Evolution of the Beetle Hind Wing, With Special Reference to Folding (Insecta, Coleoptera)

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING (INSECTA, COLEOPTERA) Dmitri N. Fedorenko EVOLUTI...

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING (INSECTA, COLEOPTERA) Dmitri N. Fedorenko

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING (INSECTA, COLEOPTERA)

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

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A. N. SEVERTZOV INSTITUTE OF ECOLOGY AND EVOLUTION RUSSIAN ACADEMY OF SCIENCES

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING (INSECTA, COLEOPTERA) by

DMITRI N. FEDORENKO

Edited by

Sergei I. Golovatch

Sofia–Moscow 2009

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING (INSECTA, COLEOPTERA) by Dmitri N. Fedorenko Edited by Sergei I. Golovatch

First published 2009 ISBN: 978-954-642-494-5 (paperback) ISBN: 978-954-642-495-2 (e-book)

© PENSOFT Publishers All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the copyright owner.

Pensoft Publishers Geo Milev Str. 13a, Sofia 1111, Bulgaria [email protected] www.pensoft.net

Printed in Bulgaria, July 2009

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

TABLE OF CONTENTS Introduction

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Material, methods and terminology

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Structure and operation of insect wings: some backgrounds 17 The insect wing 17 The hind wing of Coleoptera 21 Wing structure: basic elements and their genesis through evolution Fore wing, or elytron 27 Wing venation and elytra-body interlocking 29 Hind wing 33 Wing shape 35 The articular region 38 Fold- and flexion-lines 49 Hind wing venation 51 Secondary supporting structures 74 Folding pattern 78 Evolution of the hind wing in Coleoptera 87 The main folding patterns (folding types) 87 The folding apparatus 102 The supporting system 110 The wing as a whole 119 Morphological and morphofunctional types 120 The main evolutionary trends and functional wing types Size evolution of the imago 135 Conclusion 139 Hind wing structure and evolution in particular beetle groups Adephaga 143 Myxophaga 155 Scirtoidea 157 Staphyliniformia s.l. 159 Hydrophiloidea s.l. 162

132

143

27

5

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Scarabaeoidea 164 Staphylinoidea 171 Elateriformia s.str. 174 Elateroidea 178 Byrrhoidea 184 Buprestoidea + Dascilloidea 185 The cucujiform wing 187 Derodontoidea 188 Bostrichoidea 189 Lymexiloidea 191 Tenebrionoidea 192 Cucujoidea 198 Chrysomeloidea, Curculionoidea and Cleroidea Cleroidea 202 Phytophaga 204 Chrysomeloidea 204 Curculionoidea 205

201

Morphological evolution of the beetle hind wing and the phylogeny of Coleoptera 209 Relationships of individual beetle taxa based on hind wing structure Adephaga 213 Staphyliniformia 224 Elateriformia 229 Bostrichoidea 236 Tenebrionoidea 237 Cucujoidea 243 Chrysomeloidea 248 Curculionoidea 248 References

250

Appendix 1 Appendix 2 Appendix 3

263 323 333

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

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INTRODUCTION The beetles, Coleoptera, or Scarabaeida, is the most diverse insect order comprising about 360,000 extant species. These are arranged into four suborders, a few series, 16 superfamilies and ca 160–170 families in the most recent classifications (e.g. Lawrence & Newton, 1995). Among holometabolan insects (Endopterygota), the Coleoptera is prominent because its origin seems to have been a direct result of strong transformations of its flight apparatus. More specifically, archetypal beetle features, especially the adult external structure transformed into a durable protective construction, resulted immediately from a strongly increased defensive function of the fore wings. Having transformed into rigid elytra, these reliably prevented the hind wings in repose and the hindbody terga from damage or some other troubles when the imago penetrated into any liquid, closed or running substrate, or, on the contrary, left a confined space after preimaginal development. Formation of such a structural plan of the adult body brought about profound change in the entire flight apparatus. Functional posteromotorism, the hind wings longer than the elytra and thence reducible in length when not in use were the main sequels to this process. The great variety of body shapes and sizes, together with the immense taxonomic diversity of Coleoptera, contributed much to the diversity of hind wing venation and folding patterns. Nevertheless, the understanding of the general trends that defined this diversity is far from complete. Many studies have been restricted to hind wing venation in separate beetle families or, more seldom, superfamilies. Comparative analyses of venational characters across the order are singular. Some of them are out of date while some others seem superficial. In particular, Ganglbauer’s (1892) well-known venational typology has been shown to be largely artificial, with its carabidiform, cantharidiform and staphylinidiform venation types often being only stages of successive veinal reductions (Ponomarenko, 1972). A comparatively recent typology introduced by Wallace & Fox (1980) has not been widely adopted. Special emphasis was put on folding patterns by Forbes (1926), but with no or minimum relation to wing venation. As a result, Forbes’ typology proved to largely be functional. Nonetheless, the placement of a few families in the Adephaga, for which a separate suborder, Myxophaga, was afterwards

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

erected (Crowson, 1955), as well as the incorporation of the Hydraenidae into the Staphylinoidea, and the Haplogastra shown to be a natural group became greatly appreciated novelties of his classification based on this typology (Lawrence et al., 1995b). Thus, phylogenetic reconstructions and higher level classifications of the order, proposed to date from analyses of wing structure, have been supported by separate characters regarded as set elements, not parts of the whole, these being interrelated and thence interdependent in their changes through evolution. Such an approach obscures the intrinsic trends of evolution both of the wing as a whole and of its integral parts, forbidding the separation of synapomorphies from homoplasies. Hence, it leads to warped results and is less efficient. The objective of this work is to fill in this gap.

MATERIAL, METHODS AND TERMINOLOGY

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MATERIAL, METHODS AND TERMINOLOGY Hind wing structure, namely venation, articular region, folding pattern, tracheation of the main veinal stems, sclerotization patches, flexion lines, and mesorelief of the wing membrane were studied in members of Recent beetle families listed in Appendix 2, as well as in individual representatives of Ephemeroptera, Orthoptera, Dermaptera, Dictyoptera, Plecoptera, Megaloptera, Neuroptera, Trichoptera, Lepidoptera, Mecoptera, Diptera and Hymenoptera. Some of these are depicted (Figs 8, 9, 12–14, 22–24). Unfolded wings were mounted on glass slides with a transparent adhesive and then examined under the stereoscope at magnifications of 8× to 56×. All convex (mountain) and concave (valley) folds were identified in isolated, non-fixed, mostly dry wings; these were examined first folded and then stepwise unfolded in water or glycerol. Mesorelief peculiarities of the wing membrane were explored in a drying drop of water. The left and right wings were largely examined using more than one specimen, usually 2–10, of each species listed. Most of the folding patterns thus obtained were checked on in paper models. The following three parameters were measured: the length of the body (BL), the length of the wing (WL) and the length of the apical membrane (ML) (Appendix 3), with further analyses of the indices WL/BL (%) and ML/ WL (%). WL was measured in a fully unfolded wing, from its apex to the posterobasal margin or articular region in the case of a strongly reduced jugum or clavus plus jugum. ML was measured from wing tip to the anterior tip of the apical hinge or to the distal costal pivot (Polyphaga), or to the proximal costal pivot (Archostemata, Adephaga). In the text, the term long(er) wing or long(er) apical membrane corresponds to a high(er) value of WL/BL or ML/WL ratio, respectively, unless otherwise stated. Information on the structure of fore and hind wings of extinct Coleoptera was predominantly extracted from the literature (Ponomarenko, 1969, 1972, 1975; Nikritin, 1977; Nikolajev, 1995; Krell, 2006). Only the hind wing imprint of an Upper Permian insect was examined, probably that of a beetle labelled “PIn AS USSR, № 3286/4±, Udmurt ASSR, right bank of Kama River, dividing range of Rassokha and Kasyanovka rivers, 1.5 km NE of Chepanikha,

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

boring 121–k, depth 44–48, coll. E.I. Ulanov”. Below, this is referred to as the beetle protowing (Fig. 1). The venational nomenclature (Redtenbacher, 1886; Comstock & Needham, 1898–1899; Comstock, 1918; Forbes, 1922) is used, with slight later modifications (Balfour-Browne, 1943; Ponomarenko, 1969, 1972; Kukalová-Peck & Lawrence, 1993; Fedorenko, 2002, 2003) (Figs 2 and 3). Each of the longitudinal veinal stems from C to Cu is recognized as forking into the anterior (A) and posterior (P) veinal sectors. The hierarchy of successive forks is supported, firstly, by numerical and, then, alphabetical and other symbols. Schematically, the anterior media, MA, is accepted as first forked into MA1+2 and MA3+4, then MA1+2 forks into MA1 and MA2, while MA1 into MA1a and MA1b, and MA1a into MA1a' and MA1a". While in use here, the subdivision of the anal system into sectors AA and AP is of no fundamental significance lying in recognizing this as a pterygote protofeature. This is rather done for convenience so as to simplify the veinal symbols. Likewise, to avoid bulky symbols, cross-veins ra–rp, ma–mp, mp1+2–mp3+4, mp–cua, cua–cup and cup–a1 are designated as r, m, mp, m–cu, cu and cu–a, respectively. Symbols CuA1 and CuA2 are used instead of CuA1+2 and CuA3+4 for the same reason. The prefix basi- or symbol B (e.g., basicubitus, BCu, or basimedia, BM) is attributed to more or less strongly transformed bases of the respective veinal stems where these adjoin the articular region. The nomenclature of the sclerotization patches in the wings of Polyphaga is original (Fig. 4). In designating components such as folds and ﬁelds of the folding pattern, I follow Forbes (1922, 1926; Fedorenko, 2004a) (Figs 5, 6). The term area is used for the wing region that does not change its position during folding (most areas) or slightly turns in the wing plane (areas W and Q). Field is the wing region that becomes inverted after each elementary step of folding. Simple and double lines correspond to concave and convex folds, respectively. The ﬁrst letter in the symbol used for a fold reﬂects the ﬁeld it belongs to while the second letter points to the adjacent area or ﬁeld. The principle is the same in designating folds of ﬁeld group I (Fig. 6). Exceptions to the rule are as follows: (1) Radiating folds of apical folding sector E–X are designated each as en or xn, n = 0, 1, 2…; (2) la is an abbreviation for the longitudinal axial fold (see below). (3) The last letter of the fold name reﬂects its relative position, either anterior (a) or posterior (p), or distal (d), or proximal (pr) of the folds belonging either to (a) ﬁeld J2, i.e. the postjugal lobe, or (b) weak and rarely occurring ﬁelds K and N, or (c) ﬁelds Be, Ba and Bi in the wings of Scirtoidea. All the names of folding patterns speciﬁed by Forbes (1926) derive from those of higher beetle taxa. Many of them, e.g. Haplogastra, Dryopiformia, Diversicornia, Serricornia, etc., are currently out of use. To avoid confusion resulting from the introduction of new names, I retain most of the older names, but modify

MATERIAL, METHODS AND TERMINOLOGY

11

1

2

3

Figures 1–3. Hind wing structure of Coleoptera: the imprint of an Upper Permian beetle (the beetle protowing) (1), reconstructed groundplans of beetle wing venation after Forbes (1922) (2) and Ponomarenko (1969) (3).

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

4

6

5

Figures 4–6. Hind wing structure of Coleoptera: a generalized pattern of membrane sclerotizations in Polyphaga (4), a generalized folding pattern (5), the elaterid folding pattern (6). In Figs 5 and 6, concave (–) and convex (+) folds correspond to ordinary and double lines, respectively.

them into adjectives in quotation marks and use for particular folding types only, albeit without direct relation to taxa used at the times of Forbes. For instance, Forbes’ Dryopiformia is replaced by a “dryopiform” folding pattern. Double quotation marks are also applied to some terms or symbols in common use which are treated here otherwise than elsewhere, “Rr” and “r–m” serving as examples. The illustrations of beetle wings are moved into Appendix 1 (Figs A1–236); hereafter these ﬁgures are referred to as, e.g. Fig. A135 or Figs A24–27, or Figs A: 45, 57–59, 107. Fold- and ﬂexion-lines are dotted in the ﬁgures and supplied either with symbol ⊕ or when convex or concave, respectively. The same symbols, (+) or (–), are used in the text. The identiﬁed folds were marked on

MATERIAL, METHODS AND TERMINOLOGY

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most of the depicted wings. Some accessory or irregular folds were sometimes omitted as unnecessary details. All speculations concerning how and to which extent these or those wing parts are or may be involved in ﬂight have been made based on literature information alone. The wing is considered here as a morphological system of high complexity, in which the integral parts are organized in hierarchic order. The term archetype is used for such a system, its meaning varying depending on a particular aspect of the study. In full measure, this holds true for the present work, in which both typological and evolutionary aspects are closely intermixed. The typological archetype (Schmalhausen, 1964, 1982; Meyen, 1978; Lyubarsky, 1996) of a taxon or organism, or of something else, means the whole. This consists of its own parts, termed mera when one deals with an organism, and defines these parts, including their interrelations with both one another and the whole, according to the particular relation of each part to the whole, e.g. its position or function in the whole. The archetype is invariant, but includes all of the individual variants it defines. Mera of higher rank in the hierarchy are archetypes relative to the mera of lower levels. An evolutionary aspect of my study requires the use of Haeckel’s notion of archetype, i.e. prototype or groundplan. This is a hypothetic organism or its part which is supposed to have been ancestral to a particular taxon and thus had a complete set of the most primitive (plesiomorphous) characters. According to Beklemishev (1994), each subsequent, derived prototype is deduced from the previous one up to the Recent taxon in consideration. It is evident that when so reconstructed, morphogenesis is reduced to a monodimensional transformation series for separate characters only. Evolutionary changes in multilevel morphological systems are accompanied by character transgressions along with numerous parallelisms and convergences. General trends in the evolution of these systems become identified from comparisons between the evolutionary trends in their inherent parts. It is also quite clear that typologies proposed in the present paper for the wing as a whole and, especially, its parts, the folding pattern in particular, stand far away from the natural taxonomic classification of Coleoptera. Development of these typologies has been expedient rather than an objective, since the identification of stable wing morphotypes and folding patterns has become basic for further deductions of the relationships between them as well as between the taxa they define. Discrepancies between the typological archetype and prototype are well illustrated by comparing the “diversicorn” and elateroid folding types. Hence, the former pattern both is related to the latter as prototype and, at the same time, includes some of its special derivatives.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Phylogenetic reconstructions made for different groups of Coleoptera have resulted from mental analyses of the similarities or differences in wing structural plans, or wing types. The lack of a character matrix in the present work is only due to practical difficulties. These are largely rooted in substantial, often fundamental differences revealed between the trends of evolution in various beetle groups and no less significant discrepancies in wing groundplans of these groups. As a result, a transformation series across the order Coleoptera should have been divided into a number of sections for some lower taxa, with characters in one series often to be coded different from those in others. Since a character matrix would have become necessary for each superfamily or family, a general matrix is hardly achievable at all. Symbols used in the text and figures ac – axial ligament, or axial cord

cpde – external cpd

ah – apical hinge (= fold dq or e0)

cpdi – internal cpd

ahII – secondary apical hinge

cpdv – virtual cpd

aj – apical joint, reinforced ah

cpp – proximal costal pivot

ANP – anterior process of the notum

MNP – middle process of the notum

cp – cubital pivot

pjl – postjugal lobe of the wing

cpd – distal costal pivot

PNP – posterior process of the notum

cpdd – double cpd

teg – tegula Wing venation:

AAP – vein AA3a"+(AA3b+(AA4+AP1+2))

med – medial sclerite of pmp

al – anal loop

mcl – mediocubital loop

anarc – anal arculus

mch – mediocubital hook, or mcl open anterobasally

anarc.c. – complex anal arculus

Mr – recurrent media, the anterior part of mch

arc – arculus

o – oblong cell

arc.c. – complex arculus

pmp – proximal medial plate

cb – costal bar, or costal axis

rb – radial bar, or radial axis

cbz – costal bending zone

rc – radial cell

MATERIAL, METHODS AND TERMINOLOGY

cbzII – secondary costal bending zone

“r–m” – “radiomedial cross-vein”

cc – carpal cell

rml – radiomedial loop

cj –costal joint

rms – “radiomedial” spur, abruptly truncated base of (RP3+4+MA)+MP1+2

cub – cubital sclerite of pmp

RMP – vein (RP3+4+MA)+MP1+2

cubz – cubital bending zone

“Rr” – recurrent “radius” (RP+MA)

cuj – cubital joint

rsp – radial spur, remnant of RP1+2 base

Cur – recurrent posterior cubitus

scw – subcostal window

cw – costal window

tcu – cubital tracheal stem

dmp – distal medial plate

tm – medial tracheal stem Deformation lines:

bf – basal fold

la – longitudinal axial fold

cf – claval furrow

pjd – postjugal distal fold

hf – humeral fold

pjpr – postjugal proximal fold

hw – principal fold

phf – humeral furrow

jf – jugal fold

rf – radial furrow (Adephaga) Sclerotizations:

aas – antero-apical sclerotization

pas – postero-apical sclerotization

aas' – secondary aas

pcas – postcosto-apical sclerotization

abs – antero-apical basal sclerotization

pcs – postcubital sclerotization

ams – anteromedian sclerotization

pjs – postjugal sclerotization

as – apical sclerotization

prs – postradial sclerotization

cas – costo-apical sclerotization

pst – pterostigma

cs – central sclerotization

pst.c. – complex pterostigma

icsa – intercubital anterior sclerotization

pstII – secondary pterostigma

icsp – intercubital posterior sclerotization

SV, SVn – secondary “veins”

js – jugal sclerotization

TV – tertiary “veins”

mas – medio-apical sclerotization

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

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Fields (A–J, K, N, S, X) and areas (Q, P, T–W): A – medial

K – radial

B – proximal pivotal

Ka – radial adephagan

Ba – proximal pivotal anterior

N – intercubital proximal

Be – proximal pivotal external

R – third costal

Bi – proximal pivotal internal

S – central

Bs – staphylinid

Sa – central caraboid

C – anteromedial

X – postero-apical

C – anteromedial caraboid

Xh – medio-apical

D – distal pivotal

P – first costal

E – antero-apical

Q – second costal, or radial

F – anal

T – wedge

G – intercubital distal

U – cubital

H – principal (H1, H2 – its derivations)

V – outer anal

Ia – elateroid (intercalary) anterior

W – oblong

a

Ip – elateroid (intercalary) posterior

WING STRUCTURE

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STRUCTURE AND OPERATION OF INSECT WINGS: SOME BACKGROUNDS The insect wing The insect wing is considered to be subdivided into a (true) alar area and an articular region, or axilla, through which the alar area is articulated to the notum (Fig. 7). The neopterous alar area is in turn subdivided into three principal regions, the remigium, the clavus and the jugum, or the jugal lobe (Wootton, 1979), with the claval furrow, cf, and the jugal fold, jf, serving as lines of demarcation, respectively. As shown by Wootton (1979), the subdivision of the neopteran alar area into the remigium and the vannus by Snodgrass (1935) is unacceptable in many cases, because the vannus, or the anal fan, and consequently the vannal fold separating the vannus from the remigium occur only in the hind wings of Polyneoptera. Moreover, the vannal folds in the wings of Plecoptera, Dictyoptera and Orthoptera are known to be non-homologous (Brodsky, 1987). I think the vannal fold is secondary as compared with jf and seems to be not a jf shifted forward, as Brodsky (1987) believed, but is the anteriormost of the folds once added to jf to fanwise fold an enlarged anal region. Articular region. According to the classical, yet a more or less strongly modified scheme (Snodgrass, 1909, 1935; Wootton, 1979; Brodsky, 1988, 1989), the articular region in Neoptera is composed of three axillaries (1Ax, 2Ax, 3Ax) and the proximal median plate, m, or pmp. The basal hinge, bh, and the basal fold (bf) immediately extended into jf in the alar area separate the axilla from the notum and the alar area, respectively (Figs 7, 22, 23). The posterodistal border of the axilla passes along the outer border of 3Ax. 1Ax and 3Ax serve to articulate the alar area to the following three processes of the alinotum: anterior (ANP), median (MNP) and posterior (PNP) (Brodsky, 1989). MNP is superimposed on the basal margin of 1Ax which is in turn superimposed on ANP. In flight, 1Ax rotates on bh, i.e. in the stroke plane, whereas it adheres to a convex side margin of the notum in a folded wing. The caudal process of a rather small 3Ax is articulated to a pointed PNP. During folding, the axillaries hinge on bh and two more folds. For convenience, the latter are termed here the first (if1) and second (if2) interaxillary

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

folds, one lying between 1Ax and 2Ax, the other between 2Ax and 3Ax+m. As a result, concave and convex folds alternate in the line bh––if1+–if2–– bf+. Some of these folds have been reported to be more (bh) or less (if1) strongly involved in flight (Wootton, 1979). The region of the alar area adjacent to pmp is termed distal medial plate, m', or dmp. Some authors (Snodgrass, 1952; Hamilton, 1971; Emelianov, 1977) recognize dmp and pmp as the median plate proper and an anterior lobe of 3Ax, respectively. Wing venation. Veins as constituent parts of wing venation are cuticular tubes sclerotized on one or both sides of the wing surface. A vein serves for haemolymph circulation and protects the trachea and nerves, if any, from damage. Braced in a particular way with one another, veins reinforce the wing membrane and thus provide the wing with the necessary ratio of rigidity to flexibility. The basal sections of stronger veinal trunks and/or the narrow loops they form serve as the main supporting elements in the wings of many extant insects. Reinforced C, Sc, R and usually also the base of RP (or RP+MA) combined are considered to constitute the main mechanic axis of the wing (Brodsky, 1979), the former two or three veins supporting its leading edge. The first anal vein, 1A, performs a similar function in the trailing wing area (Brodsky, 1979). The remigium’s posterior part is supported with both branches of Cu or only one, anterior (CuA), of them. Longitudinal veins are connected through cross-veins, which add to the strength properties of the wing-supporting carcass. Some cross-veins serve as

Figure 7. Principal regions of the neopterous wing. Subdivision of the remigium into the basal part and the apical membrane is only attributed to the Coleoptera.

WING STRUCTURE

19

principal braces at pivots or joints. They localize wing deformations and restrict movements of the main axial supporting elements relative to one another. The wings are costalized in most of the pterygotes: in the course of evolution, longitudinal trunks of the anterior half of an originally symmetrical protowing have become stronger and shifted forward in (sub)marginal position. The posterior part of a costalized wing is freed from veins completely or in part. Deformation lines. There are lines that weaken or interrupt the veins they intersect in the wing membrane of most pterygotes. With no special regard to the function each of them performs, the lines have usually been termed folds or sutures (Emelianov, 1977; Brodsky & Ivanov, 1983; Brodsky, 1987), or, according to function, subdivided into fold-lines, or folds proper, and flexion-lines, or furrows (Wootton, 1979, 1981). The folds serve for folding the wing into a resting position, the furrows contribute to wing deformations during flight. Flexion-lines. The following principal flexion lines (as “folds”) have been recognized (Brodsky & Ivanov, 1983; Brodsky, 1987): (1) that of the radial sector, (2) a cubital fold, and (3) a transverse fold. Further two furrows have been specified in the hind wing of Sialis: (4) a medial “fold” and (5) a longitudinal “fold” between the apical branches of the radius-sector. The former two furrows are supination lines; therefore, they are concave and more strongly developed than the latter two that are convex pronation lines. The transverse furrow is also convex, but it largely reveals itself during flight when the wing apex deflexes at the end of a downstroke. In a different nomenclature (Wootton, 1979, 1981; Brackenbury, 1994), the flexion-lines (1) to (3) have been referred to as the medial line, the claval furrow, and the transverse flexion-line, respectively, without (4) and (5) being specified. Grodnitsky & Morozov (1994) introduced the terms remigial and remigio-anal furrow for the medial line and claval furrow, respectively, because they reasonably considered both these lines as highly adaptive and therefore varying in position in different insect wings. As a result, the new names proved to be in no way referred to a particular vein, thus better describing insect wings in flight. The claval furrow, cf, is the principal flexion-line occurring in generalized fore and hind wings. This is always well-developed at least in the basal part of the wing. In Neoptera, cf is of strict position as primitively lying between Cu and A, while intersecting BCu. These peculiarities make cf a reliable marker in identifying veins it is associated with in many neopteran wings. However, in derived wings, the described interrelations between cf, Cu and A hold true only for the wing basal part or even the very wing base, whereas the more distally located cf often migrates forward, in between Cu branches. This occurs e.g. in Papilionidea, some Neuroptera, Paraneoptera and Coleoptera.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Folds. The folds are almost passive elements, yet they facilitate and direct deformations of a folding wing. The wing of a generalized structure is equipped with the only convex fold, the jugal fold which was often referred to as the anal fold. I refrain from using the latter term because it was also applied to the claval furrow or the vannal fold. The jugal fold emerged from folding both wing pairs roof-wise (Rasnitsyn, 1980b; Brodsky, 1988). The other longitudinal folds, if any, are secondary in pterygote wings. These are chiefly radiating vannal folds which serve for flat fan-folding of the entire anal area, the vannus. This occurs in the hind wing of Polyneoptera alone. Flight kinematics and deformations. Flapping insect wings deform in a particular way and generate vortex rings during the beat cycle. Interaction of these vortices with both one another and the wing produces net lift and thrust. Supination, pronation and deflexion of the wing apex are principal flight deformations. The wing supinates at the beginning of an upstroke. It flexes first along the medial and then the claval furrow. The wing thus becomes concave, with its leading edge being directed upwards. The beginning and subsequent development of supination is related to wing torsion. This is under control of the clavus (plus jugum), which prevents the wing’s basal region from twisting (Brodsky & Ivanov, 1983; Brodsky, 1994). Therefore, no torsion usually occurs in the wings with a large clavus. On the contrary, it is the wings which are narrow basally and normally operate with high beat frequencies that appear most strongly twisted (Grodnitsky, 1996). A complex torsion articulation is present to supinate and twist the wing. It occurs at the wing base where the remigial and claval furrows converge. The main mechanic axis of the wing pivots on this articulation relative to the rest of the wing. At the end of an upstroke, the wing pronates. Its leading edge becomes directed downwards, and the wing slightly flexes along pronation lines. A camber takes place because the wing’s posterior part is flexed. During a downstroke the wing remains flat or weakly convex. A transverse deformation of the wing occurs in many insects. It develops in the wing affected by inertial forces at the end of a downstroke. Then either the wing apex or entire alar area except at base becomes deflexed downwards; this deflection can be smooth or abrupt, with a transverse furrow observed in the latter case. Wing folding. The following four types of longitudinal folding are generally recognized: roof-like ancient, roof-like proper, flat and contour, the latter three types being known in extant insects. A roof-like folding is hypothesized to have been an endopterygote wing protofeature (Rasnytzyn, 1980b; Brodsky, 1989). Folding starts with rotation of 3Ax initiated by wing flexor contracting. This muscle is either t–p 14 or t–p 13 (Hemiptera, Mecoptera, Hymenoptera), or both (Brodsky, 1989). At the wing base, there are one or two mechanical systems responsible for folding, the toggle-joint system and/or the abutment system. The

WING STRUCTURE

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latter is best developed in the hind wings of Coleoptera, Megaloptera, Trichoptera and Lepidoptera (Brodsky, 1989). Adduction of the wing is accompanied by tucking the posterobasal wing sector or jugal lobe (= jugum). When folded over the abdomen, the wings of various pterygote taxa are fixed in a particular way.

The hind wing of Coleoptera Two lines of research concern beetle wings. In the first, comparative-morphological, wing characters taken separate or combined with other characters were utilized in constructing classifications and/or phylogenies of Coleoptera, with the minimum or no reference altogether to function. These studies vary considerably from one another in the amount of available material. Among them, most dealt with wing venation across certain families or, more rarely, superfamilies (e.g., Good, 1925; J. Wilson, 1930; Maŕan, 1930; S. Wilson, 1934; Procházka, 1936; Saalas, 1936; Marçu, 1939; Balfour-Browne, 1940, 1943; King, 1956; Jolivet, 1957, 1959; Khalaf, 1970; Suzuki, 1970, 1994; Ward, 1979; Pasqual, 1982; Zherikhin & Gratshev, 1995; Dolin, 1975, 2000). Only a few concerned the whole order (Forbes, 1922, 1926; Crowson, 1955; Ponomarenko, 1973; Wallace & Fox, 1975, 1980; Kukalová-Peck & Lawrence, 1993, 2004). Works in which wing characters were used to diagnose or describe beetle taxa, mostly of the genus- or family-group level, are virtually countless. Comprehension that the wing is an integrated system, not a mere set of characters, comes from morphofunctional studies. These show how wings of different structure operate in flight or folding, how the constituent parts of a wing operate and co-operate and how much each part contributes to the whole. However, the methods used in these investigations of folding and, especially, flight are so toilful that only a few, model beetles have been studied yet. Nothing is known about microscopic Coleoptera in flight, in which the wings operate with low values of Reynolds number (Weis-Fogh, 1975). The articular region. Comparative morphological analyses of the axilla have shown that the Coleoptera is monophyletic and closely related to the Neuropterida (Megaloptera, Raphidioptera, Neuroptera) and the Strepsiptera (Hörnschemeyer, 1998). Coleoptera have been classified as Adephaga + Archostemata + (Polyphaga + (Myxophaga + Buprestidae)), with interrelationships of most of the beetle series, superfamilies and families remaining unresolved. The results obtained imply that the morphological features of the axilla are only of limited use in evaluating the affinities between higher coleopteran taxa. Hence, I can only suggest that the characters of the axillaries which underlie several recent phylogenies of Scarabaeoidea (Browne et al., 1993; Scholtz et al., 1994; Browne

22

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

& Scholtz, 1996, 1999; etc.) could in part be overweighted. Following Brodsky (1989, 1994), Hörnschemeyer (1998) also emphasizes that nothing supports the origins of the axillaries and median plates due to clustering of smaller ancestral sclerites, as believed by Kukalová-Peck & Lawrence (1993). Typologies of wing venation and venational groundplans. The first venation type recognized was “Adephaga”, or carbidiform, or caraboid. It is its distinctions, the rich venation in particular (numerous cross-veins and a well-developed oblong cell), that inclusion of Paussidae, Gyrinidae, Dytiscidae and Carabidae in the suborder Adephaga was supported by Burmeister (1841, 1854). Later, Ganglbauer (1892) specified the following two venation types, the staphyliniform (or staphylinoid) and cantharidiform (or cantharoid). The former was characterized by very few or no cross-veins and a few longitudinal veins combined, with the latter type being intermediate between the other two types in combining a few crossveins, but no oblong cell. This classification has been shown by Ponomarenko (1972) to largely be formal, because its types often reflect nothing more than successive venational reductions developed in parallel by many Coleoptera. Yet, the above types prove convenient for describing particular wings, especially in identification keys and taxonomic descriptions. A different typology (Wallace & Fox, 1975, 1980) is currently not in use.

Two reconstructions of beetle venational groundplans are well-known among the others (Figs 2, 3), those of Forbes (1922) and Ponomarenko (1972). The former resulted from a comparative analysis of extant Coleoptera, the latter focused on the wings of extinct beetles, especially the beetle protowing (Fig. 1). The fact that the protowing imprint bears a complex folding pattern similar to that of extant Coleoptera was put forth as a weighty argument in favour of this imprint belonging to a beetle. However, some of its features are not characteristic of Endopterygota. This especially concerns the basal brace between M and Cu, namely, the presence of m–cua versus mp–cua in the extant beetles. Given the shape and large size of the protowing, the latter character makes it look much more similar to the hing wings of plecopterans and their allies. Nevertheless, features of the beetle protowing have been utilized in some recent reconstructions of hind wing groundplan of Recent Coleoptera (Fedorenko, 2003, 2004a, b, 2006). Folding patterns. Forbes (1924, 1926) was the first who focused on the folding and folding patterns of beetle wings. He specified and homologized the integrants of folding patterns, as well as classified them and defined the principal ways of folding. He also subdivided the patterns into main two types, “Adephaga” (+“Archostemata”) and “Polyphaga”, the latter comprising the (sub)types, or series, “Haplogastra”, “Diversicornia”, “Bostrychiformia” and “Dryopiformia”. Forbes considered “Haplogastra” the most primitive subtype of “Polyphaga” in bearing a greater part of the characteristic features of “Adephaga”. The subtype “Diversicornia”, or “normal group”, was subdivided into two variants linked together by transitions. Among them, “Clavicornia” actually conformed

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to the groundplan of “Polyphaga” while “Serricornia” was derived. The subtypes “Bostrychiformia” and “Dryopiformia” were recognized as derived from “Diversicornia”, with “Dryopiformia” considered as the most advanced. Among the above patterns as specified by Forbes, “Archostemata”, “Adephaga” and “Haplogastra” are only more or less natural. In contrast, “Diversicornia”, “Bostrychiformia” and “Dryopiformia” are not natural, as they embody externally similar derivatives of different groundplans. In other words, Forbes’ typology proved in part functional and reflecting only the general trends of evolution of beetle hind wings. Peculiarities of flight kinematics and deformation of coleopteran wings. Since transformed into rigid elytra, the fore wings in flight produce no thrust, but generate lift while undergoing a considerable drag (Nachtigall, 1964; Schneider & Hermes, 1976; Grodnitsky, 1999). When promoted, they flap with low amplitudes or remain immovable. The latter holds true for Adephaga (Schneider, 1978; Grodnitsky & Morozov, 1995; Grodnitsky, 1996, 1999) and Buprestidae. Sometimes the elytra lose the flight function from being strongly shortened or immobilized (some Scarabaeidae), or owing to a special position in flight. The latter case implies that promoted elytra can be set immovable above and perpendicular to the dorsal surface of the body, as observed in some Buprestidae (Grodnitsky & Morozov, 1995). In addition, Brackenbury (1994) reported that Nicrophorus lays the elytra inverted roof-wise above the abdomen.

Grodnitsky (1996) considers that an extended, thus elongated, wing working area was what could have redressed the wing loading on the hind wing since increased by a reduced flight function of the elytra. The wing aspect ratio (AR = 4R2/s, where R is wing length and s is wing surface area) is high and reaches 3.1–3.9 in the studied species. Some other kinematic parameters are as follows (Grodnitsky, 1996): wing loading (Pw = P/S; P, weight of the imago; S, surface area of all wings) is high (3.7–15.5), but comparable with the respective values for Diptera or Hymenoptera. Hind wing amplitude on the average ranges between 140 and 170º, but often it reaches 180º (Brodsky, 1988), yet not surpassing 60º for the elytra. Wingbeat frequency is considerable and ranges between 30 and 120 Hz. The wings of big-sized morphologically dipterous beetles (Cetonia or Pachnoda, Cetoniinae, Scarabaeidae) operate with higher beat frequencies (~100 Hz), lower amplitudes (95º) and high wing loading (41.3 N/m2) (Magnan, 1934; Weis-Fogh, 1973; Grodnitsky, 1996; Schneider, 1997; Haas et al., 2000). These indices show beetle flight to be high-powered (Grodnitsky, 1996), but with highly limited or no reserves of power (Marden, 1987). The results obtained for flight deformations using different model objects and methods are somewhat conflicting. In particular, the wing in tethered flight has been shown to be slightly cambered during a downstroke, with a posterodistal gutter observed. During an upstroke, the wing is slightly concave and only sometimes supinates along the claval furrow (Grodnitsky & Morozov, 1994).

24

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

In contrast, Brackenbury (1994) reported that the wing in unimpeded flight strongly supinates along the claval furrow and still more so along the remigial one. He also pointed that a strong deflection of the wing apex intensifies supination of the wings with a short apical membrane (Hemicrepidius, Elateridae; Cantharis, Cantharidae; Agapanthea, Cerambycidae). In Cicindela (Carabidae), Oxyporus (Staphylinidae) and Nicrophorus (Silphidae), the wings at the end of downstrokes strongly deflect downwards at their base and weakly so all along their length while the pterostigma in operation triggers off supination. A characteristic feature of most Coleoptera is wing claps, i.e. contacts between wingtips, on the turning points of up- and downstrokes. These effects generate either additional lift in larger insects or thrust in smaller ones. Folding of the hind wing at rest. Different aspects of folding and unfolding have been studied (Schneider, 1975, 1978; Blum, 1979; Hammond, 1979; Kukalová-Peck & Lawrence, 1993; Brackenbury, 1994; Haas & Wootton, 1996; Haas et al., 2000; Haas & Beutel, 2001). In particular, the fine mechanics of folding has been investigated, with mathematic models schemed for describing this process (Haas & Wootton, 1996; Haas, 1998). In addition, fundamental differences have been shown to exist between Coleoptera and other pterygotes (Dermaptera, Blattodea) in the way and mechanisms of transverse foldingunfolding of the hind wing (Haas & Wootton, 1996; Haas, 1998, 2006; Haas & Kukalová-Peck, 2001). More specifically, adduction of the wing to the body, with the jugal lobe tucking, is followed in beetles by semi-automatic transverse folding. This base-to-tip kinematic chain of elementary folding steps is primitively triggered off by a decreased angle between the costal and cubital (CuA) bars. These in turn are modified to be more flexible in their apical sections. Among the modifications, a strong and smooth bending zone developed just proximal to the radial and oblong cell, respectively, has been recognized as beetle protofeatures (Kukalová-Peck & Lawrence, 1993; Beutel & Haas, 2000) while angulate bends occurring on wing supporting axes as derived. As external agents, the elytra and, especially, the abdomen are involved in folding the wings of many species (Hammond, 1979). “Pumping” movements of the abdomen push the hind wing beneath the elytra, with spiculate patches on the abdominal terga contributing much to the efficiency of this process. Immobilization of a folded wing is often due to a close contact between two highfriction binding spiculate patches, one in the wing and the other in the elytron. More important, however, is the lock between the subalare and the basalare button, on the one hand, and HP and BSc, on the other, this locking mechanism being synapomorphic to Endopterygota (Hörnschemeyer, 1998). In some beetles (Scarabaeidae, Coccinellidae), resilin was found in highly deformable regions of the wing (Haas et al., 2000). At last, a few functional

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25

folding types were specified in several papers reviewed above. Some authors (e.g. Blum, 1979; Brackenbury, 1994) derive folding patterns of higher complexity from simpler ones. I can only comment that these suggestions seem to be improper, albeit quite logic a priori. Venational nomenclature. All hitherto proposed nomenclatures of beetle wing venation can be reduced to two general ones. The first was a special case of the classification of Comstock & Needham (1898–1899; Comstock, 1918) who used Redtenbacher’s (1886) terminology. This scheme was followed by most authorities of the early last century (Kolbe, 1901; Snodgrass, 1909; Graham, 1922; Kempers, 1924; d’Orchymont, 1920, 1921; etc.), as well as by some relatively recent students. Its principal weakneses were amended by Forbes (1922) who showed that Comstock & Needham’s costa and media in the beetle hind wings corresponded to the subcosta and cubitus, respectively, in the other pterygote wings. Since then, it is this scheme that was most widely used in the works devoted to the wing venation of Coleoptera. Its several points were corrected afterwards, namely, the vein termed the first anal was reasonably renamed into Cu2 (CuP) (Balfour-Browne, 1943; Ponomarenko, 1969, 1972). Some other veins became interpreted differently as well. For instance, cross-veins of the oblong cell in Adephaga were considered branches of the media (Balfour-Browne, 1943; Wallace & Fox, 1975, 1980). Numerous earlier interpretations of beetle wing venation were reviewed by Jolivet (1957, 1959). Recently, Kukalová-Peck & Lawrence (1993, 2004) proposed a new nomenclature, one which in general is barely different from that of Comstock & Needham. It is based on the idea of Kukalová-Peck (1978, 1983) concerning the origin of the insect wing which is supposed to be a strongly modified exite, a small, annulated, freely articulated appendage of the epicoxite, the latter hypothesized as the proximalmost segment of the thoracic leg. The presence of eight veinal pairs, i.e. PC, C, Sc, R, M, Cu, A and J, is considered a protowing feature of pterygotes. Each pair, composed of two alternatively fluted sectors, a convex anterior (A) and a concave posterior (P), was articulated to the tergum via a band of four ancestral sclerites as follows: basivenale (B), fulcalare (F), axalare (A) and proxalare (P). Neopteran pteralies are believed to be composite clusters originated through fusion of some of the ancestral sclerites, only the median plate consisting of a single ancestral sclerite, the median fulcalare (FM). As the main argument against Forbes’ nomenclature, its application to the beetle wing has been stated to make the veins M, Cu and AA articulated with the axillaries and the median plate otherwise than in the remaining neopterans. Namely, (1) M has no basivenale, (2) Cu is associated with the median plate (pmp), not 3Ax, (3) some anal veins start from BCu. In addition, (4) the anal area is very large, with anal veins richly branched, which is rather characteristic

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

of orthopteroids than endopterygotes. Finally, the beetle radial cell lies between R (RA) and RS (RP), whereas when occurring the pterostigma is to be located between RA1+2 and RA3+4 in endopterygote wings. The latter point remains unclear because the homology of the beetle radial cell to the pterostigma has not been grounded at all. Introduction of the new nomenclature does not eliminate the above “disagreements”, so it simplifies nothing, but appreciably troubles homologization between the wing structures of the coleopterans and those of other neopterans. This is so first because all veinal systems, beginning from the radius-sector (RP) and the distal section of the radius (RA), prove to be removed one step backwards as compared with those in Forbes’ nomenclature. To solve the problems, the authors had to admit a number of ill-grounded assumptions. Thus, the former M was included into RP as its posterior branch (RP3+4) while the arculus between the former M and CuA became MA, or a “medial bridge”. So interpreted, the latter vein acquired the reverse orientation by being directed basad, not apicad, thus displaying a very unusual condition for a strong longitudinal vein. The claval furrow had to be renamed into a “mediocubital fold” while the “fold” termed “claval” proved reduced. Owing to the latter novelty, the beetles became a group standing apart from the other Endopterygota whose characteristic feature was the presence on the wing, or at least at its base, of a well-developed claval furrow. Avoiding a discussion of the theoretical grounds of this new system, I can state that the views of Kukalová-Peck & Lawrence (1993) concerning beetle wing venation seem largely erroneous, whereas Forbes’ scheme is correct at least in interpreting the major longitudinal veinal stems. Many conclusions drawn by those authors seem dubious as resulting from comparisons between nonhomologous structures. Among them, the conclusion is illustrative which proclaims that many peculiarities of the beetle wing occurred nowhere else but in very primitive basal Palaeozoic insects. Closer relationships between Coleoptera and Megaloptera supported by a great similarity of both groups in wing venation or wing articulation (Forbes, 1922; Ponomarenko, 1972; Brodsky, 1988; Hörnschemeyer, 1998) were omitted. From this a curious conclusion emerged that the ancestral Pterygota had diverged before a protowing was transformed into an asymmetrical wing necessary for flapping flight. In my opinion, such conclusions partly stemmed from the incorrectly interpreted relations between M and Cu, on the one hand, and the axillaries, on the other, in beetle wings. Besides this, the homology of at least some of the structures of the beetle axilla to particular “protowing sclerites” cannot be accepted as well-documented. This is especially true of “BAA” and “BAP”, as well as some 3Ax integrants, such as “AXJ”, “FJ”, etc.

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WING STRUCTURE: BASIC ELEMENTS AND THEIR GENESIS THROUGH EVOLUTION Beetle fore and hind wings are organs, i.e. integral parts of the flight apparatus. For the hind wing’s alar area as archetype, these parts are two functional apparatus, flight and folding ones. Each apparatus embodies its own supporting system and deformation lines. The entire wing venation and furrows altogether constitute the flight apparatus, the remigium’s venation combined with folds are integral parts of the folding apparatus. The integrants of both apparatus overlap: several folds serve as furrows, and many supporting structures of the remigium are involved in wing folding. It seems useful to specify separate elements of a merely structural archetype before considering them as interrelated parts of the whole. This archetype is chiefly definable by the wing shape, venation and deformation lines combined. Although wing venation as wing support is a whole, it is divisible into longitudinal veins, each of a particular grade in the hierarchy of forking, and crossveins. Deformation lines are subdivided into folds and furrows.

Fore wing, or elytron A defensive function became the main for beetle fore wings since they had been transformed into rigid protective devices, or the elytra. The elytra also protect the meso- and metanotum, as well as the abdominal tergites and hind wings at rest. At a certain evolutionary stage, they also became involved in a complex and joint defensive construction along with the pterothorax and abdomen. As the defensive function of the elytra intensified, these lost flexibility and put on weight stepwise, thus lowering their flight function to lift generation alone. New functions arose instead. Some of them resulted from a developed closed subelytral space. This enabled the beetles to better thermoregulate and prevent desiccation, as well as the aquatic beetles to breathe under water. Both the internal structure of the elytron and the development of its main types, i.e. cancellated, striated and smooth, were described by Ponomarenko

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

8

9

10

11 Figures 8–11. Fore wing structure: Wesmaelius sp., Hemerobiidae, Neuroptera (8); Sialis sp., Sialidae, Megaloptera (9); a hypothetic groundplan venation of the Coleoptera, left elytron (10); the groundplan structure of the Adephaga, left elytron. The elytral disc intervals and their tentative homologues are marked with Roman numerals I–XI.

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(1969) in detail. Briefly, the elytron started to form through the multiplication of cross-veins. As a result, wing venation became similar to the archedictyon. Veins of this, false, archedictyon divided a not or feebly thickened wing membrane into many irregular cells. These were then arranged into two or three rows between true longitudinal veins conformable to the primary elytral intervals in the sequel. The veins separating cells of the rows that bordered on one another were lined lengthwise, thus being transformed into secondary longitudinal veins, or secondary elytral intervals. These became indistinguishable from the primary intervals or nearly so. As the cells were reduced in size, they started increasingly being modified into vertical tubular columellae. The bottom of such a cylindrical columella was composed of the wing membrane, and its wall involved surrounding veins’ walls. As the cylindrical columellae evolved into conical structures, the striated elytral type replaced the cancellated (alveolar) one. Completely reduced columellar cavities left the elytron smoothed out dorsally. The cancellated elytron was and still is a characteristic feature of cupedoid archostematans first. Striated and smooth elytra prove to occur in many extant and extinct Coleoptera. The elytron is thus a trilaminar structure: its dorsal and, to a lesser extent, ventral layers are composed of dorsal and ventral veinal walls, respectively, the columellae bracing these layers are of lateral walls of the neighbouring veins, and the internal cavity pierced with columellae is homologous to the veinal cavity. A thick and strongly sclerotized dorsal layer together with columellae chiefly support the rigidity of the elytron. The ventral layer is usually either weakly sclerotized or, not rarely, desclerotized and comparable in firmness with the wing membrane. The elytron of Adephaga, Carabidae in particular, is generally the least advanced in structure. This shows all of the basic elements of a true wing; among them, all three axillary sclerites are weakly modified while 2Ax is even less strongly derived than that of the hind wing. Ventrally, the basal 1/3 elytron has retained the bases of RA and 1A (AA1+2), as well as rudimentary bases of RP+MA and of some other veins (Carabus, Calosoma, Cicindelitae). As a remnant of the jugal lobe, a well-developed alula also occurs, bearing the vein AP4 and the axial cord. An alula has also been retained in some Hydrophilidae. Wing venation and elytra-body interlocking The most complete venation of the fore wing is generally recognized to have been that of extinct Tshekardocoleidae (Ponomarenko, 1969; Kukalová-Peck & Lawrence, 1993). However, when identifying particular veins this pattern was composed of, veins of the jugal lobe (A4 in particular) were sometimes erroneously placed in the elytron proper (Ponomarenko, 1969). In addition, a strong

30

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

vein was designated as CuA (Richter, 1935; Rohdendorf, 1949; Crowson, 1955) even though it was rather weak at the wing base of Megaloptera (Fig. 9). A new venational groundplan of the beetle elytron is here proposed to eliminate these disagreements (Fig. 10). According to this groundplan, there were the following veinal trunks at the base of the elytron: C+ScA and RA rimmed the elytral side margin (morphologically, the costal one) and the edge between the epipleuron and the disc, respectively, while ScP passed along the epipleuron. The veins of the elytral disc were subdivided in two groups, radiomedial and anal ones, separated from each other basally. M took off from RA near, and RP+MA caudal to, the shoulder. The anals were the following four: AA1+2 (1A), AA3a", AA3b and AA4+AP1+2. Among them, the former was the strongest vein, and the latter was distinct only near the scutellum. In contrast to tshekardocoleids with their oblique, humerus-to-tip directed, longitudinal veins on the elytra, extant beetles are largely distinctive in having these veins reduced in number and also directed lengthwise (Fig. 11). This difference resulted from the veins changing in position, which came chiefly out of the anals turning with their distal sections laterad (morphologically, anteriad) and the apices drifting along the elytral suture caudad (morphologically, distad). Some longitudinal veins, including a greater part of the apical branches of RP+MA and MP, should have been reduced in the course of this alteration. Seven unbranched veins have only survived. These correspond to uneven intervals on the elytron of the striated type. Usually, each of these intervals is supplied with a trachea inside and bears a row of setigerous punctures on its dorsal surface. Even elytral intervals are secondary while those beginning with interval 5 onward are likely to be complex. The epipleural ridge, as well as intervals 5 and 3 are composed of RA, AA1+2 and AA3a", respectively; 9th at the apex is represented by one of RP+MA branches, apparently RP2; 7th conforms to MP–(MP+CuA) in the middle of the disc, and to CuA, or, less likely, MP–MP3+4 behind the middle; 1st is formed by fused AA3b and AA4+AP1+2. One secondary interval inserted between two primary ones appears to have become an optimal structure for the striated-type elytron. In the elytral groundplan of extant beetles, two or more secondary intervals at most could be located between interval 9 and the epipleural ridge. Regardless of frequent multiplications of separate or all intervals, one must conclude that the striate elytron could have borne eleven or twelve intervals in the groundplan. Recent Coleoptera have retained not more than eleven intervals, 10th being rarely developed as strongly as the rest (e.g. in Amphizoa, Apotomus, Byturus, etc.). Usually, it is reduced entirely or in part, being only distinct either in the

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anterior (e.g. Elateridae) or posterior (numerous carabids) part of the elytron in the latter case. On the undersurface of intervals 1 and 9, as well as the anterior, broadened part of the epipleuron, certain devices have been developed to interlock the elytra at rest into each other, the pterothorax and the abdomen. The first elytral interval is responsible for the elytra to interlock along the suture: these become locked when a narrowly carinate ridge of one elytron fits into a deep groove of the other, more often the ridge being placed on the left elytron. Sometimes a double lock of similar structure occurs which contributes to the tenacity of such a coupling of the elytra. The pterothorax constitutes an integral part of elytra-body locking. An elevated mesoscutellum overlaps and presses the prescutellary interval from above, thus fixing the elytra at their bases. The metascutal alacrista fixes the anterior portion of the elytral interval 1, this being modified into a more or less sharp ventrolateral carina. Many beetles have developed additional devices to lock the elytra, among them the mesepimeron, metepisternum, metacoxa and abdominal sternites or only some of these sclerites grooved or excavated flat along the epipleural edge to fit it better. An earlier elytra-body interlocking mechanism seems to have been simpler; the elytra clinging to the body apparently played the leading role, perhaps in couple with the friction between hairy surfaces of the elytra and the body. These opposing hairy surfaces then could have been modified into or replaced by binding patches of high friction. Laterally, such a patch extended from the metepimeron to the abdominal apex or at least a few anterior sternites, e.g., in Elateridae. The opposing patch on the elytral undersurface extended along the epipleuron. In extant beetles whose elytra interlock likewise, the opposing binding patches of one couple are usually confined to the metepimeron and a broadened portion of the epipleuron. The above mode of elytra-body locking is characteristic of free-living beetles whose elytra are affected by nothing that could unlock them. Other Coleoptera have developed additional locking devices, a carinate undersurface of elytral interval 9 occurs most frequently among them. Together with the epipleuron, it forms a narrow groove that receives and thence fixes the lateral edges of one to a few abdominal sternites. Ponomarenko (1969) believes that such a device was an adaptation of aquatic or riparian beetles to prevent the elytra from being discoupled by the air stored inside the subelytral space. Yet exceptions to the rule are frequent. In particular, a carinate interval 9 appears to be present in many cucujiform families, e.g. Coccinellidae, Mordellidae and Curculionidae.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

The internal carina of elytral interval 9 strongly varies in length from one beetle taxon to another. It can be either short, pocket-like, situated in the middle of the elytron (middle carina) or long, extended to the wing apex. A fairly short middle carina apparently locking only into abdominal sternite 2 was peculiar to such extinct archostematan families as Rhombocoleidae, Catiniidae, Schizophoridae and Triaplidae. A carina of very similar structure occurs, e.g., in Dryopidae, Elmidae, Histeridae and some Hydrophilidae. A fairly long, though apically weak (reduced?) carina has been found in Buprestidae (e.g. Buprestis, Dicerca), some Agyrtidae (Pteroloma) and a number of cucujiform beetles. In some byrrhoids (e.g. Byrrhus), the carina is interrupted medially, thus being divided into two separate carinae, one middle, and the other pre-apical. The Adephaga is the best example of how this locking device could have evolved. The groundplan might be the situation present in extant Trachypachus, Trachypachidae, Amphizoidae and Hygrobiidae. This is interval 9 which is not or barely thickened throughout its length and set apart from the epipleural ridge. Some Dytiscidae (e.g. Dytiscinae and Colymbetinae) show a similar pattern. Most other Hydradephaga and carabids possess interval 9 modified into a more or less sharp and high carina. The carina is still homogeneous in some dytiscids (e.g. Hydroporus) and rather primitive carabids (Carabus, Calosoma, Nebria, etc.), but becomes differentiated in most other adephages. The caudal part of the carina grows to be superior, thereby transforming into a small, rounded, subapical lobe directed outwards. The posterior edge of this lobe either remains beneath the elytron or enters its lateral edge before the apex. As the lobe progresses, the basal- and apicalmost sections of the former carina tend to degenerate. An apical part is retained distinct near the elytral suture in Hydradephaga and some Carabidae, but disappears in most representatives of this latter family. The best-developed subapical lobe occurs in Paussitae, some Dytiscidae (Hyphydrus) and Rhysodidae. In rhysodids, it is especially strong and shifted towards the elytral suture, the latter character probably resulting from the former. Nevertheless, it is as likely interval 7 as interval 9 that could have given rise to the lobe. Both carinate interval 9 and its derivations tended to be obliterated in Adephaga whose elytra and/or abdomen were modified in the course of adaptive radiation. Thus, the carina has disappeared in many interstitial groundbeetles with flat or shortened elytra. This happened also in cicindelites adapted to flashing rapidly. The Gyrinidae with its highly movable telescoped abdomen appears to have lost the carina for secondary reasons, too. A different interlocking mechanism is peculiar to e.g. Systolosoma. What serves to lock the elytra in this beetle genus is a couple of small lobes on abdominal sternite 7. Unlike the internally carinate elytral interval found in most other Adephaga, these erected lobes are superimposed on the elytra apically.

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33

It seems the immense adaptive radiation in Coleoptera, with their penetration into various substrates and environments, was chiefly due to the adult body of high structural integrity, especially the elytra as an integral part of the body. Several hypotheses have been proposed to explain why the fore wings of beetle ancestors transformed into the elytra, among them the defense against predators or protection of the flight-wings from damage when moving in a confined space, subcortical for example (Crowson, 1955), or in wet habitats. The other hypotheses relate the origin of the elytra to the formation of an increasingly closed subelytral cavity. This could become necessary either to breathe under water (Heberdey, 1938) or to minimize water losses under the conditions of dry climates in the Lower Permian (Kukalová-Peck, 1991).

Hind wing Wing homologies of Coleoptera to other endopterygotes strongly depend on which particular groundplan of the beetle wing is to be selected among those proposed to date. This holds especially true for wing venation. Reconstructions by Forbes (1922), Ponomarenko (1972) and Fedorenko (2003) are based on an unbranched anterior cubitus (CuA). Proceeding from this statement, some veins in the wings of Recent Coleoptera hardly agree with the groundplan. In particular, I failed in bringing the apical branches of MP and CuA in Archostemata, Adephaga and Polyphaga into accord with one another. These disagreements have been eliminated by introducing a two-branched CuA in the wing groundplan of Coleoptera (Figs 15 and 16). This (1) enables me to minimize speculations concerning particular veins in beetle wings and, as a result, (2) adds to the similarity between Coleoptera and Megaloptera in the venational groundplan of the hind wing (Figs 13 and 14). The other main distinctions of this venation pattern are as follows: (1) the arculus (arc) as the basalmost brace between M and Cu veins, occupying as it does this position in beetle wings, is designated as m–cua; (2) RP base is considered as strongly shifted distad from its much more proximal primary position; (3) MA throughout its length except its base is accepted merged in RP and, then, RP3+4 as the posteriormost branch of RP. Such a position of arc, namely, m–cua instead of mp–cua, is uncharacteristic of Myrmeleontidea; hence, this character requires or at least enables one to consider it derived. The branchpoint of M shifted distad and resulting from merged MA and MP bases seems to have been the most probable way to achieve the pattern (Fig. 16). Such a treatment leaves separate veins of derived venation patterns still more complicated, the complex arculus (arc.c.) and CuA base in the wings of Archostemata and the bulk of Polyphaga (Figs 18 and 20) being among them.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

12

13

14 Figures 12–14. Hind wings of Megaloptera and Neuroptera: an undetermined Chauliodinae, Corydalidae (12); Sialis sp., Sialidae, Megaloptera (13); Wesmaelius sp., Hemerobiidae, Neuroptera (14).

WING STRUCTURE

35

15

16

Figures 15–16. Hind wing groundplans of Coleoptera, hypothetical successive stages. Dotted lines correspond to folds, shaded regions to fused veins.

Demarcation between the remigium and the clavus in the wings of Coleoptera is lined along the anterior (or the only) branch of the claval furrow (see below), starting at its base and then just behind CuA–CuA2. Wing shape Beetle wings vary in shape, but often resemble one another in this character in medium- to big-sized members of not only one and the same but different families. Usually, only the smallest beetles show special wing contours. Wings of

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

17

18

19

Figures 17–19. Hind wing groundplans of Coleoptera: Adephaga (17), Archostemata (18), Schizophoroidea (19). Designations same as in Figs 15–16.

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37

20

21

Figures 20–21. Hind wing groundplans of Coleoptera: Polyphaga (20), the cantharoid wing type (21). Designations same as in Figs 15–19.

smaller Dytiscidae, Scirtoidea and Drilidae are the broadest while the wings of most of Hydradephaga (Gyrinidae, Haliplidae, Noteridae) approximate them. The narrowest wings occur in many Staphylinoidea, Histeridae, Jacobsoniidae (Sarothrias), Nitidulidae, some Cerambycidae, larger Coccinellidae and, with no relation to body size, numerous Curculionoidea. Fairly slender wings are also present in some Carabidae and many Scarabaeoidea. The hind wing of a triangular shape, with the anterior margin straight and slightly oblique at the apex, is most frequent. In this wing, probably groundplan, the apex is fairly narrow, situated level to or slightly before the middle of wing width, more strongly rounded anteriorly than posteriorly. Along the posterior

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

margin, the wing is moderately convex to, more rarely, almost straight, with no or an indistinct jugal incision. A primitive jugal lobe is more or less evenly rounded and broad. The maximum wing width varies in position lengthwise, on the average being situated at or before midway. A common trend in the evolution of the above wing type is very weakly expressed. It manifests itself in transforming a triangular contour into a more or less oval one as the adult body decreases in size. As a result, the clavus and jugum become reduced in whole or in part. More often, this alteration is mediated or accompanied by an increasingly deep jugal incision, this tendency being general for beetle wings in the course of body miniaturization. Invertedly triangular (Figs A: 59, 142) or oblong-oval (Figs A: 109, 152, 172, 173, 187, 236), or semilunar (Figs A233–235), or more or less falcate (Figs A: 47, 62, 67), or, seldom, rectangular (Fig. A197) shapes are extreme specializations. Of them, the latter two have resulted from shifting the wing tip caudad while the others have anyway been related to reduced clavus plus jugum. More specifically, the invertedly triangular wing has emerged from the combination of an attenuated wing base and the maximum wing width shifted distad. The oblong-oval wing is in fact the previous pattern supplemented by a (more) widely rounded wing apex. A narrow wing base, combined with a forward shifted wing tip, defines the semilunar wing. Narrower wing bases chiefly occur in smaller or, more rarely, larger (e.g. Scarabaeoidea) beetles. More or less stalky wings are observed in the smallest beetles, accompanying very long apical membranes in very long wings. A shorter and wider abdomen and/or a weighty body induce the wing to be broader near the middle, especially so at the base, to prevent the vortex ring from contact with the body (Brodsky, 1986, 1987). A falcate wing is supposed to contribute to an easier development of the apical vortex (Brodsky, 1987). An almost separated jugal lobe analogous to the dipteran alula appears to be a device to change wing working area (Grodnitsky & Morozov, 1994).

The articular region The Coleoptera (Figs 25–33) corresponds well to the general pattern of the axilla. Some misinterpretations raised by applying it to beetle wings (Snodgrass, 1909) were corrected by Balfour-Browne (1943). The basic distinctions of the Coleoptera are as follows: (1) a small mediobasal sclerite articulated with the wing flexor (t–p13 and t–p14) is detached from the 3Ax body and (2) pmp is more or less distinctly split into two sclerites, each protecting a large tracheal stem. The Adephaga is peculiar in having an addi-

WING STRUCTURE

Figure 22. Hind wing base of Arcynopteryx sp., Plecoptera, dorsal aspect.

Figure 23. Hind wing base of Sialis sp., Sialidae, Megaloptera, dorsal aspect.

39

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

tional process (PMNP) of the alinotum articulated with a considerably elongated posterobasal process of 1Ax. PMNP is the longest, superimposed on PNP in Gyrinidae. It has also been reported in Corydalus, Corydalidae (Brodsky, 1989). Kukalová-Peck & Lawrence (1993) treat the median plate (pmp) as a single ancestral sclerite, FM, which, in beetles, is secondarily divided into two ones, FM1 and FM2, each articulated with the anterior (BMA) or posterior (BMP) medial basivenale, respectively. In my opinion, that the above sclerites belong to the M-system alone, not to the M- and Cu-systems as follows from Snodgrass (1935), demands weighty arguments in support. The medial origin of “FM1” and “FM2” needs to be sustained by their closer contacts with the elements of 2Ax of the same nature, namely, “AxM”. Yet beetle sclerites articulate with one another otherwise. When

Figure 24. Hind wing base of Chauliodinae gen. sp., Corydalidae, Megaloptera, dorsal aspect.

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41

well-developed and separate (e.g., in Archostemata, Adephaga, Staphyliniformia), “FM1” is always associated only with 2Ax (AxM) while “FM2” with 3Ax. The latter connection is so prominent that “FM2” often looks like nothing but a process of 3Ax (e.g. Carabidae, Histeridae), suggesting “FM1” to be of medial, and “FM2” of cubital, origins. The tracheae of “BMA+FM1” and “BMP+FM2” being independent, confirms this. Namely, there occur four tracheal stems at the wing base of Adephaga (e.g. Amphizoa, Acilius, Calosoma). These are: tr, tm (“MA”), tcu (“MP”) and ta (“Cu”+“A”). The medial trachea (tm) emerges from the 2Ax basal part, then it passes through the “FM1” area and enters “BMA”; thereafter it gets into R and goes further parallel to the radial trachea (tr). Level to the anterior arculus (m–cua), tm fuses shortly with (or, e.g., in Dytiscus, passes close to) the cubital trachea (tcu), and then it gets separate again and enters the vein “RP”. The common tracheal stem tcu+ta forks at the 3Ax base into tcu, entering “FM2”, “BMP” and “MP” in succession, whereas ta forks into taa3+4 and tap at the 3Ax apex. Nothing follows from the above but “FM1” = FM, “RP” = MA, “BMA” = BM, “BMP” = BCu, “the medial bridge” = m–cua, “MP1+2” = CuA. “BCu” could have been recognized as BAA only. “BAA” is not a basivenale, but a strongly reduced “cross”-vein that braces the bases of the neighbouring anal veins on each side of the jugal fold. Here “BCu” and “BAA” are considered as a remnant of the vein AA4 and the vein AP3–AP3a, respectively. When in use elsewhere, the terminology of Kukalowa & Lawrence (1993, 2004) requires the “ancestral” sclerite “FM2” to be renamed into FCu while “FCu” into FA. In my opinion, “FA” is to be recognized as a secondary structure. Given the corrections made, it seems appropriate to apply the names medial (med) and cubital (cub) sclerites to FM and FCu, respectively. As regards the median plate (pmp) as a whole, it seems better to be termed a mediocubital plate or mediocubital lobe of the 3Ax. Although med and cub vary strongly within Coleoptera both in appearance and peculiarities of their contacts with 2Ax and 3Ax, med is always articulated with 2Ax while cub with 3 Ax, the respective trachea being traced well in case of either of the sclerites is reduced proximally. More or less subequally developed, uninterrupted, band-like med and cub chiefly define primitive beetle groups (Archostemata, Scirtoidea, Hydrophiloidea, Staphylinoidea, Dascilloidea, some Elateroidea, Byrrhoidea, Bostrichoidea, Lymexiloidea, Figs 28 and 29). The median plate (pmp+dmp) in Archostemata seems to be of the most primitive structure. In their wings, contiguous med–BM and cub–BCu most closely resemble flattened veinal bases; cub at the base is fused with 3Ax, being also in contact with the 2Ax body. Adephagan pmp+dmp is hardly derived: a well-developed cub is fused with 3Ax basally, being separated from 2Ax (Figs 25–27). The sclerite

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

med tends to be reduced in size. It becomes detached from 2Ax or, seldom, also from BM (Calosoma, Carabidae, Figs 25 and 26), but disappears in Rhysodidae alone. Most polyphages show the opposite tendency, one towards an entire med, coupled with a partly reduced cub, the latter either attenuating basally (some Elateroidea and Byrrhoidea; Bostrichoidea) or interrupted in the middle by

25

26 Figures 25–26. Hind wing base of Calosoma, Carabidae, dorsal (25) and ventral (26) aspects.

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43

the basal fold (most Scarabaeoidea, Elateroidea, Tenebrionoidea, Cleroidea, Chrysomeloidea, Curculionoidea and Cucujoidea, Figs 30–33). More rarely, the distal portion of cub disappears totally. The interrelations of cub with 2Ax and 3Ax in Polyphaga are similar to those in Archostemata. However, in separate polyphagan groups (Dascilloidea, Buprestidae, Byrrhoidea: Callirhipis) the contact between cub and 3Ax tends to weaken in the course of cub shifting anterobasad, with its base drifted towards 2Ax. That pmp in beetles is divided into two can be explained with the assumption that Coleoptera and Megaloptera are closely allied, with many structures of the coleopteran hind wing derived from those of the megalopteran one. In particular, Megaloptera (Figs 23 and 24) show a pmp composed of no other sclerite but what is quite conformable to the cub in the beetle wing. In front of this sclerite, a large, more or less oval, membranous window is situated crossed by the basal fold. Towards the 2Ax base the medial trachea passes through the window, implying that the area around the trachea is to be homologous to med of the beetle wing; therefore, pmp composed of cub alone might have been a beetle protofeature. If so, a beetle autapomorphy is not a pmp split into two parts, but med as a novelty. However, beetles might have also developed a bipartite pmp from a much more primitive pmp similar to that of Plecoptera (Brodsky, 1988), the latter pmp being evenly sclerotized and occupying the entire region between 2Ax, 3Ax and bf (Fig. 22). Based on this evidence, pmp of Gyrinidae

Figure 27. Hind wing base of Graphoderus, Dytiscidae, dorsal aspect.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

seems to be the most primitive among the beetles. It is composed of a large entire sclerite separated from 2Ax by a narrow membranous zone crossed by the if2 fold. The Amphizoidae shows a similar pmp structure, but this similarity appears to be secondary as their wings are out of use owing to atrophied wing muscles (Beutel, 1995). Further transformations of pmp (as well as the entire axilla) were obviously affected by flight and folding deformations peculiar to a particular wing type. To resist the coacting deformations as one or both wing functions intensified, a more flexible and more rigid pmp seems to have been necessary. This was modified in different ways, separate or combined, including changes in the shape and relative position of med and/or cub, and/or structuring pmp through, e.g., its corrugation (Gyrinidae). BM and BCu as constituent parts of a pattern close to the groundplan (Gyrinidae) are obviously separated by a deep furrow extended to m–cua. In the other beetles, this furrow declines step-by-step, but seldom disappears completely. Earlier stages of this reduction seem to have been influenced by the claval furrow, which resulted in the distal part of BM compressed, shifted beneath and merged into BR.

Figure 28. Hind wing base of Hydrophilus, Hydrophilidae, dorsal aspect.

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45

1Ax. The first axillary is subdivided in the beetle wing (Kukalová-Peck & Lawrence, 1993) into a more or less triangular tail articulated with the notum proximally and with 2Ax distally. The posterobasal process of the tail is fairly long in Adephaga, Myxophaga and Dascillidae (Kukalová-Peck & Lawrence, 1993). The remaining dascilloids, Buprestidae and some Byrrhoidea are to be added here. In the rest of the Polyphaga, the posterobasal and posterodistal processes are subequally long. The tail is extended forward into a comparatively narrow neck ending in a more or less widened head. At least in some beetles, the 1Ax head and neck are ventrally reinforced with a longitudinal carina. The carina is well-developed in Adephaga and some Polyphaga, running closer to the proximal edge of the neck in the former versus the distal edge in the latter. The head is extended into a ventral process which is bent downward and articulated with BSc. 2Ax. The second axillary is subdivided into a broader body and a comparatively narrow and long arm, the latter taking off from the anterior part of the body and directly extending into BR. In the groundplan, both the body and arm are well-developed. The arm is often partly to completely reduced (desclerotized), Carabidae (Fig. 25) and some Scarabaeoidea (Fig. 30) being the best examples. The arm is also absent from the wings of some Histeridae (Fig. 29), Cerambycidae (Agapanthea) and a number of large-sized members of various polyphagan families.

Figure 29. Hind wing base of Pachylister, Histeridae, dorsal aspect.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

3Ax. The third axillary in beetles is divided into the body, or 3Ax proper, and a small basal fragment articulated with the wing flexor. 3Ax varies considerably in size and shape from group to group. In Archostemata and Adephaga, it is fairly small, with a longer or shorter, but narrow head, which is often strongly bent outwards, and a rather short and narrow caudal process. 3Ax of such a structure seems to be close to the beetle groundplan. The Polyphaga, perhaps only excluding Haplogastra, shows a larger 3Ax supplied both with a fairly short head, which is usually feebly curved outwards, and an obviously elongated and broadened caudal process. This larger 3Ax is most likely secondary, resulting from the inclusion of a sclerotized wing membrane contiguous to the outer edge of an initially small sclerite. The border between this secondary sclerotization and the sclerite proper is well traced in some beetles. It is this border that appears to have been recognized as the suture between “ancestral sclerites” (Kukalová-Peck & Lawrence, 1993). 4Ax as depicted by Brodsky (1989, fig. 7) is nothing else but the secondary sclerotization. That Adephaga and Polyphaga differ in the structure of 3Ax can be explained by the particular way in which the jugal lobe becomes tucked during folding the wing at rest. In Adephaga, 3Ax+pmp functions as an integral part of the jugal lobe which hinges on the basal–jugal fold. This way of folding is

Figure 30. Hind wing base of Netocia, Scarabaeidae, dorsal aspect.

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47

based on a close contact between 3Ax and the anals of the jugum. This is attained by 3Ax and AP4 drawn together, resulting in a longer contact between them: either 3Ax bends strongly to better fit vein AP3+4 (Dytiscidae: Colymbetinae, Laccophilinae; Hygrobiidae) or 3Ax and vein AP4 become parallel due to a ┐-shaped curve of the latter (Carabidae). In most polyphages as opposed to adephages, a very small postjugal lobe (see Figs 31–33; A: 92, 103, 202, 217, 225, etc.) connects 3Ax to the jugal lobe during folding. The former lobe results from a couple of secondary folds radiating from near the 3Ax head. Of them, the posterior fold, pjpr+, passes along the outer, secondary border of 3Ax while the anterior one, pjd–, lies far behind AP4. An immediate contact between 3Ax and the jugal lobe occurs in Polyphaga as well, though not too frequently and probably secondarily. In this case, a strongly sclerotized vein-like strip often develops to support the posterobasal wing margin. This postjugal sclerotization

Figure 31. Hind wing base of Ctenicera, Elateridae, dorsal aspect.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Figure 32. Hind wing base of Mylabris, Meloidae, dorsal aspect.

Figure 33. Hind wing base of Temnoscheila, Trogossitidae, dorsal aspect.

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49

is immovably fused to the caudal process of 3Ax (Figs 28 and 30) and serves for 3Ax to more easily manipulate the jugal lobe. All the above characters are attributable to beetle wings of a more or less generalized structure. Considerable, sometimes profound, transformations of the axilla are observed chiefly in the wings with a partly to completely reduced anal area, especially in larger beetles (some Buprestidae and Scarabaeidae). Certain Histeridae taken as an example of a strongly shortened basal part of the wing (Fig. 29) show all axillaries, especially 3Ax, hypertrophied, with the arm of 2Ax lost.

Fold- and flexion-lines It is hardly possible to strictly separate folds from furrows in beetle wings, as some folds serve as flexion-lines (Brackenbury, 1994) while certain furrows are involved in flight. Topological and evolutionary interrelations of these multifunctional wing structures are complex (Grodnitsky & Morozov, 1994; Grodnitsky, 1999). Because folds were novelties for the beetle wings, some of them should have emerged from furrows as zones of wing weakness. Likewise, since formed, folds of “appropriate” position grew to serve as furrows. In addition, some fold associations, mostly internal triangular fields, could have performed some supporting functions during flight. The claval, or remigio-anal, furrow (cf) is well-expresed at the base of both wing pairs in most endopterygotes (Figs 8, 9, 12–14, 22–27, 31–33). It seems to have evolved in beetles in the following way. Initially, cf passed between the veins CuP and AA1+2 all over their lengths. As a folding apparatus formed, the distal sections of cf appear to have given rise to the folds fu and gv, respectively. At the next evolutionary stage, cf “forked” in the basal part of the wing, since an anterior branch, cf1, was added to the former cf, now cf2. The branch cf1 derived from fold na of field N in decline, thus originally not surpassing the juncture of cu2 and CuA. This pattern has been retained by Archostemata, some Adephaga and Polyphaga. In many other polyphages, cf1 step-by-step substituted for cf2 functionally: it penetrated the barrier of cu2 and extended to the CuA2 apex, leaving cf2 reduced in part or entirely. It seems quite probable that a bifurcate cf makes supination smoother for the wing because it forms a pivot where it forks. The trailing area can thus hinge first on cf1 and then on cf2 as the wing supinates. As the clavus and jugum decreased in size in many beetles, cf declined gradually until completely reduced together with the wing trailing area. Therefore, either cf was replaced with the remigial furrow or different mechanisms of wing torsion came into operation.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

The remigial furrow seems to be heterogeneous in beetles. When represented by the anterior fold (ap) of a well-developed field A, it conforms to the basal section of the medial furrow of Megaloptera. This pattern occurs only in rather primitive beetles (Archostemata, Adephaga and some Polyphaga). In the remaining Coleoptera, the medial furrow is supplanted either by a newly formed furrow or the anterior fold (cq) of field C, the latter fold being complex in many cases as well. This variant is peculiar to the folding patterns of the “serricorn” type” and some of its analogues from the elateroid type. It is along this furrow/ fold that the wings of Cantharis spp. and Athous strongly supinate (Brackenbury, 1994). The distal section of the medial furrow of Megaloptera can be homologized with the longitudinal axial fold (la) and its derivatives (folds sd and cq) in beetle wings. The antecubital furrow (= medial fold, in the sense of Brodsky & Ivanov, 1983) is here supposed to have evolved into the posterior, convex fold (au) of field A or at least underlain it by forming a convex profile along the anterior margin of CuA. The transverse furrow is only developed in the wings with a short apical membrane. It has been shown (Brackenbury, 1994) for Elateridae, Cantharidae and Cerambycidae (Agapanthea). In these, the anterior and posterior components of the furrow conform to the folds de and hw, respectively, implying that the furrow is sure to be secondary. A concave humeral fold (hf, Fig. 27) reveals itself in unfolding wings only. It results from what the costal and cubital bars are pulled apart apically, but remain braced by the arculus basally. An angular increase between the bars is accompanied by some shift and twist of R relative to its base (R+M) and the entire region proximal to hf. The greater the angle between the costal and cubital bars, the stronger the deformation of R+M near the arculus and, thence, the more pronounced hf. Accordingly, hf is less distinct or absent (reduced) in the wings which unfold without considerably pulling apart the bases of the costal and cubital bars. The impact of hf on wing venation is chiefly weak: common effects are somewhat desclerotized and flattened veins of the wing costal margin where they are intersected by the fold. A convex humeral furrow (phf) apears to perform a function similar to that of the transverse furrow. It occurs proximal to hf in the wings of some Coleoptera (e.g. Carabidae, Coccinellidae) during flight. Recorded at the early upstroke (Brackenbury, 1994, pl.5), phf is certain to develop at the end of the downstroke or during the downstroke-to-upstroke transition to increase wing amplitude. In Adephaga, phf is a narrow zone extending from the wing costal margin proximal to the humeral vein (h) to the joint of 2Ax and 3Ax (Fig. 26). The wing structures it crosses are transformed so as to supply this zone with the maximum

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flexibility: the costa is widely desclerotized, BR is strongly attenuated and separated from BM by a rounded membranous window, and the area between the anterior wing margin and ScP is modified into a convex subcostal bulge. Then phf passes in between med and cub. Perhaps it is a well-developed phf that raises a tendency towards increasingly separating these sclerites from each other from Hydradephaga to Carabidae. The great majority of other beetles show a pattern presumably derived from the above one. In their wings, the area where the costa had been widely desclerotized was reduced from the apex, the subcostal bulge approached the costa and became still more convex, still more sclerotized and thence still more vein-like. In the wings so structured, phf appears to be non- or less functional.

Hind wing venation In interpreting the sclerites of the wing base, I would rather adhere to Brodsky’s (1988) point of view, according to which the humeral plate (HP), basisubcosta (BSc) and basiradius (BR) are treated as transformed bases of the respective veinal trunks, i.e. the costa (C), the subcosta (Sc) and the radius (R). The same holds true for dmp constituent parts, the basimedia (BM) and the basicubitus (BCu). The recognition of all these structures as separate ancestral sclerites or their clusters (Kukalová-Peck & Lawrence, 1993) seems to be ill-grounded, therefore I don’t follow their argumentation. Precosta (PC). A free precosta is generally regarded as a wing protofeature occurring in many Palaeozoic insects, but absent from the wings of Recent Pterygota. Some Auchenorrhyncha and a few beetle groups (Carabidae, Staphylinidae, Silphidae, Scarabaeoidea, Cerambycidae) have only been referred to as exceptions (Kukalová-Peck & Lawrence, 1993). However, carabids and probably also cerambycids have wrongly been placed among these families, since a desclerotized base of C+ScA has been misinterpreted as PC (Kukalová-Peck & Lawrence, 1993, fig. 22). In the remaining families listed, PC was homologized with membranous strips or flaps of the wing costal margin distal to the humeral plate. These bizarre structures, especially flaps, occur only in far advanced wings, those of certain staphyliniform beetles. That these strips or flaps are absent from the wings of much more primitive structures, including those of numerous Staphyliniformia, argues against their homologization to PC. Based on this evidence, an independent PC as a beetle plesiomorphy is rejected while the anterior wing margin is considered as being composed of the costa (C) basally and the C+ScA distal to h (= sca–scp1, or sc1). When so interpreted, C and ScA conform to the traditional PC and C, respectively.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

The humeral plate (HP) is a strong sclerite originally separated from the basisubcosta (BSc) by a weakly sclerotized membranous area. The proximalmost portion of the area is transformed into a ventral pit which receives the basalare button of the wing at rest. In dorsal view, the pit looks like a rounded and moderately strongly sclerotized field similar to that of Megaloptera both in shape and position (Fig. 23). Elateriform beetles, especially Buprestidae (e.g. Anthaxia), very closely resemble Megaloptera in this character. In most other Coleoptera, the field undergoes a progressive lengthwise compression and some shift apicad. The alteration is accompanied by sclerotization of the ventral membrane which culminates in the transformation of the field into a ventral carina of HP, this being more or less long and directed towards BSc. Apicad, HP is extended into the costa (C), the latter being desclerotized over its longer (Adephaga) or shorter (most other Coleoptera) basal section. Basisubcosta (BSc) and basiradius (BR) together form a strong joint sclerite (Brodsky, 1989; Kukalová-Peck & Lawrence, 1993; Browne & Scholtz, 1994; Fedorenko, 2002), with borders, if any, hardly traceable in between. The sclerite is composed of BSc ventrally and anterobasally, and of BR posterodistally (Figs 25–27). The base of BSc receives a long anterodistal process of the 1Ax head. BR is the immediate extension of the 2Ax arm, which is in fact the basalmost section of BR. The costa (C) is free between HP and h only. Distal to h, C is fused to ScA. As a product of this fusion, C+ScA reaches the radial cell only in the wings of extremely primitive beetles, Archostemata and Scirtoidea. In the others, it constitutes a part of the costal bar due to fusion with or merging into the subcosta (ScP). A narrow cell, the costal window (cw), lies between free C+ScA and ScP. Distal to cw, C+ScA is usually indistinct or hardly traced over a very short basal section of the costal bar. The subcosta (Sc). Following Kukalová-Peck & Lawrence (1993), I consider the subcosta as being composed of two veinal sectors, of which the anterior (ScA) is superimposed on the posterior (ScP). ScA, not alone but together with the adjacent parts of a secondarily sclerotized wing membrane, constitute a convex subcostal bulge. In the Coleoptera, ScA never occurs as a conspicuous vein, so it can only be traced in few beetles. In these (e.g. Dascilloidea; Eulichadidae), the anterior border of ScA can be homologized with a weak longitudinal furrow that passes along the subcostal bulge. Sometimes this furrow grows deeper basad (Dytiscoidea) or apicad (Carabidae), rarely almost reaching BSc in a few tiger beetles (Cicindela). When expressed not too well, ScA is nevertheless traced by the respective trachea which, together with that of ScP, rises from BSc and then passes through a bulge between the anterior wing margin and ScP. While being very

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similar to vein ScA, the bulge is in fact complex, as it embodies not only the vein proper, but also the adjacent parts of a sclerotized wing membrane. ScA is separated from HP and the costa by a triangular membranous window narrowing apicad. The window is initially weakly sclerotized and nearly reaching the humeral vein. As C and ScA approach each other in many beetle wings, the window grows reduced distally, thus making the subcostal bulge still more convex. There is no similar window between ScA and ScP, since these are contiguous proximal to h. Because of this, the “transverse” humeral vein consists of the very ScA apex and two very short veins that brace ScA with C and ScP. These “cross-veins” can be interpreted ambiguously, either as free bases of ScA branches, ScA1+2 and ScA3+4, or one vein as ScA and the other as a true cross-vein. Depending on the hypothesis selected, either both veins, the costa and the subcosta, or only one of them will be complex distal to h. To simplify veinal symbols, I recognize C+ScA as a complex vein braced by h with a simple subcosta (ScP). ScP never reaches the wing apex and can rarely be traced up to its apical juncture with RA (some Adephaga, e.g. Carabitae, Cicindelitae). Usually, ScP disappears before the apical end of the pterostigma, as in most Adephaga, or much more proximally, either within or proximal to the radial cell, as in Archostemata or Polyphaga. In the middle part of the wing extent, ScP is either contiguous to R–RA (Archostemata, Adephaga) or with no suture fused to this vein (Polyphaga). Distal to h, a free ScP runs between the costal (cw) and subcostal (scw) windows. Radius (RA, or R) and radius-sector (RP, or RS), Forbes (1922) and some of his followers (e.g. Balfour-Browne, 1943; Ponomarenko, 1969) treated unbranched RA as a protofeature of the beetle wing. They accepted RA as the vein passing close to the anterior wing margin and skirting the posterior border of the pterostigma apically. RP grew away from R about midway or a little closer to the wing apex. Then it gave more (Forbes, 1922) or less numerous (Ponomarenko, 1972) apical branches. Having compared the venation of the beetle protowing and the wings of some Megaloptera, Ponomarenko (1972) suggested that the beetle RP was in fact a jointed vein. He hypothesized a secondary base of this vein to be the oblique vein. This was commonly recognized either as the cross-vein ma–mp between RP+MA and the media posterior (MP) or a free base of the media anterior (MA). A short primary base of RP was situated in the basal half of the wing until reduced or transformed into a cross-vein in beetle ancestors. Answers to the questions where the MA+RP branchpoint was to be originally situated in beetle wings and how many branches this vein comprised vary from author to author. Thus, Wallace & Fox (1975, 1980) placed the first fork of

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

the vein proximal to field B and recognized its five apical veinal branches. Ward (1979) considered the vein forking distal to the field only into three branches. These authors accepted the posteriormost branch of MA+RP as a MA or MA fused to the posterior branch of RP. Kukalová-Peck & Lawrence (1993) treated RP ambiguously. They recognized RP as forking at the very base of the beetle protowing, but unbranched in extant Coleoptera. Forbes regarded RA as forking, with its posterior branches strongly shifted caudad and thus conformable to the RP+MA branches. I also adhere to Forbes’ viewpoint in accepting RA (Figs 15–21) as a free and unbranched vein which skirts the back margin of the pterostigma (Adephaga, Myxophaga) and shares the joint stem R (or perhaps RA+RP) with RP in the basal half of the wing. R–RA either tightly adjoins or is fused to ScP between scw and r1. When, which happens rarely, it is extended to the wing apex (Fig. A22), it seems to have been elongated secondarily. In Polyphaga and Archostemata, RA and the pterostigma combined show a tendency to total reduction. RP takes off from R–RA at about or even distal to the midway of the wing and then almost immediately is fused to MA, thus being a free vein only at its very short base. The basal, often strongly weakened section of MA is only retained in Gyrinidae (Figs A1–3) and some Dytiscidae (Eretes, Dytiscinae), being hardly traceable in Carabidae (Figs A: 14, 19, etc.). Of the two RP+MA branches, the anterior one (RP1+2) is either free (Adephaga, Myxophaga, Archostemata) or likely to be fused at its base with the caudal part of r2 (Polyphaga). The posterior branch, RP3+4+MA, is totally reduced distal to the radiomedial spur (rms), a short basal section of RP3+4+MA being free only as constituting the anterior component of “r–m” between the RP1+2 base and rms. The presence of a basal remnant of RP1+2, the radial spur (rsp), proves RP1+2 taking off from within the radial cell in Polyphaga. A vein-like RP1+2 is absent from the wings of all Polyphaga, perhaps except for Sikhotealinia (Fig. A30). A more or less strongly transformed rsp persists in some Cleroidea, Chrysomeloidea, Curculionoidea, Tenebrionoidea, Lymexiloidea (Fig. A128) and Elateridae. Since rsp is reduced, the outer border of the radial cell becomes angulate, often with a strong tracheal stem rising from the angle. Probably RP1+2 did fork, yet it is unbranched in Adephaga and Archostemata. Conversely, if the sclerotizations of the apical membrane in some polyphagan wings, especially those of Mordellidae, are considered homologous to veins, they imply that RP1+2 was two-branched. The pterostigma (pst) is peculiar to the costalized wings of numerous pterygotes. Looking like the elongated patch of a thickened wing membrane between the anterior wing margin and the subcosta or RA proximal to the wing apex, pst makes the wing to operate more effectively by maintaining an optimal angle of

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attack at the early upstroke and suppressing the flutter effect (Norberg, 1972). In Coleoptera and some Hymenoptera, pst contributes much to the automatic supination of the wing apex (Brackenbury, 1994). The above true pst is only retained in Adephaga (Figs A1–27), being totally reduced in the other beetles (Figs 34 and 35). When present in some Polyphaga, primarily Staphyliniformia (Scarabaeoidea; Staphylinidae, Silphidae, Synteliidae, Figs A: 42, 47, 49, 59, 63, 64, 66–69), well-developed pterostigma-like structures are sure to be secondary, hence to be termed pstII. Progressive evolution of the wing folding pattern brought pst to reduction, i.e. largely either the formation of the apical hinge, fold dq (= e0) (Archostemata, Polyphaga), or shifting this fold basad (Adephaga). This happened because all rigid structures distal to the hinge, including pst, strongly tended to be oblite-

a

d

e b

c

f

Figure 34. Evolution of the pterostigma, radial and carpal cells in Adephaga: Hydradephaga (a–c) and Carabidae (d–f).

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

rated, since they proved involved in the rolled wing apex (Archostemata) or its derivatives (some Adephaga; Polyphaga) during wing folding. Adephaga is the best example of how fold e0 affects pst. The latter is initially well-developed because the fold passes distal to the RA apex or intersects its very tip at best. As

b

a

d

e

c

f

Figure 35. Evolution of the pterostigma, radial and carpal cells in Polyphaga; a–f, successive stages.

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the apical membrane grows longer, the fold shifts basad, leaving an increasingly long apical portion of pst desclerotized. To balance this loss, the anterior part of the radial cell constitutes an integral part of a new, complex pterostigma, pst.c. This has been developed by many Adephaga in parallel, being best expressed in smaller Hydradephaga and Carabidae, as well as Myxophaga. The sharp posterobasal border of pst.c. inside the radial cell was wrongly recognized as a vein (Ward, 1979). The radial cell (rc, or 2r). Treatments of the veins the rc is enclosed with strongly vary from author to author. Usually the cell lying between RA and RP (or the anterior branch of RP) and limited by cross-veins proximally and distally (Forbes, 1922) is considered as the beetle groundplan. Forbes attributed this pattern to all Coleoptera but Polyphaga. The Polyphaga was distinguished by the distal cross-vein fused in part or entirely to the anterior branch of RP. The latter character is often ascribed also either to Adephaga (Balfour-Browne, 1943) or Adephaga plus Myxophaga (Kukalová-Peck & Lawrence, 1993), or all Coleoptera (Wallace & Fox, 1975, 1980). Kukalová-Peck & Lawrence (1993) concluded that rc is limited by cross-veins both proximally and distally in Archostemata alone, whereas in Polyphaga the only vein “RA3+4” skirted rc throughout but anteriorly. What could have happened to the proximal cross-vein was not clarified. I think that all groundplan components are present in Polyphaga, cross-veins r1 and r2 included (Figs 20 and 21). The veins situated proximal to r1 were only reduced (desclerotized), among them cross-vein m1, as well as the RP+MA basal section which field B intersected1 twice. An almost caraboid wing-venation pattern of some Scirtoidea (Figs A: 32, 33) confirms this was the case. In particular, the following groundplan elements occur in scirtoids: RP, crossveins r1, m1 and m3, as well as both free sections of RP+MA. Some other Polyphaga show more (Elateriformia: Byrrhoidea, Dascilloidea, Elateroidea) or less (Cucujiformia: Tenebrionoidea, Chrysomeloidea, Curculionoidea) similar patterns. Nevertheless, these are derived as showing already a developed “recurrent radius” (“Rr”). The medial system (M). There are no reliable criteria for the identification of the apical branches of the media. This is largely so because the anterior- and posteriormost of them were fused with the adjacent branches of RP and CuA at the earlier evolutionary stages of Pterygota. Since then, distinctions between the branches of different origin, but sharing the common stem became more or less conventional.

1

Schizophoroid archostematans, perhaps partly, are the only exception to the rule.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

As the above fusions formed, longitudinal veins decreased in number while the transverse braces between them became stronger. The braces which resulted from free bases of longitudinal veins fusing apically substituted for cross-veins as former primary braces, because the new braces proved much more stable both in length and position. Based on this, the brace between the main mechanic axis of the wing and the posterior border of the remigium seems to have been consolidated, strongly contributing to the structural and functional integrity of the remigium. The RP–MA brace is a feature of all Endopterygota, its presence in the hind wings of Plecoptera and even Dictyoptera implying a general evolutionary trend in Pterygota. The basal M–Cu brace occurs in the wings of most insects, including the Namurian Paoliidae, a hypothesized ancestor of the pterygotes (Rasnitsyn, 1980b). Treatments of this brace vary strongly between authors: either m–cua or mp–cua, or M5 (Tillyard, 1926; Martynova, 1960; Rasnitsyn, 1980a, b), or MP (Sharov, 1966; Kukalová-Peck, 1983; Fedorenko, 2002, 2003, 2004a, b). In Endopterygota, this strong and usually short vein takes the appearance of a mp–cua. I am rather inclined to accept this neutral interpretation of the vein. I designate it as m–cua, according to its relative position in the beetle wings, and avoid a discussion concerning its nature. Forbes (1922) termed this vein (anterior) arculus (arc). Later, it was re-named into a “medial bridge” (Kukalová-Peck & Lawrence, 1993). The vein M–MP, or the medial bar, has been retained uninterrupted in a few beetles only, some Adephaga in particular (Figs 25 and 26). In the other Coleoptera, M–MP having become desclerotized distal to arc, the medial bar evolved into a baseless vein, the recurrent media (Mr). Then, Mr tended to shorten from base until total reduction. This peculiarity strongly obscures the relations between the veins at the wing base. Nonetheless, some beetle wings allow to trace these interrelations. For example, the medial bar of Cupedidae, despite desclerotized basally, stems from CuA just distal to arc (Fig. A28). A similar pattern, but with a trachea instead of the M–MP base, occurs in polyphagan wings with a longer Mr (e.g. Elateridae, Lycidae, certain Tenebrionoidea). In Archostemata and at least some Polyphaga, M–MP is therefore fused to arc and the CuA base. Hence, two different patterns are to be specified for the Recent Coleoptera. The first is defined by independent bases of R, MA and MP, with a simple arculus, arc = m–cua (Adephaga, Fig. 17). The second pattern is derived and represents either a synapomorphy of Archostemata plus Polyphaga or, this being even more likely, a homoplasy of Archostemata plus Polyphaga but Scirtoidea1: the basal section of MA is reduced, the arculus is complex, arc.c. = M+(m–cua) 1

The Scirtoidea seems to be defined by a simple arculus; no arc.c. has been confirmed in Haplogastra either.

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while MP (or M–MP) stems from CuA (M+CuA) at a longer (Polyphaga) or shorter (Archostemata) distance from arc.c. Cross-veins between RA, RP and MA are so designated after Fedorenko (2003, 2004), except for some corrections made to simplify venational nomenclature. Strict homologization of cross-veins in the wings of Recent Coleoptera to those of the beetle protowing is rejected because the latter may actually have been not a beetle wing at all. Cross-vein m1 is present in Adephaga and Archostemata, whereas it is totally reduced in the Polyphaga, except for its certain members retaining the vein rudimentary. Since enclosed by field B, cross-vein m2 was obliterated in all beetles but some Archostemata (Omma) which retained the vein indistinct. In Adephaga, m2 persisted as a strongly transformed vein, more vein-like in a few representatives, but replaced with a sclerotized strip in the remaining taxa. Cross-vein m3 is distinct in Archostemata, some Gyrinidae, Dytiscidae, Scirtoidea and also probably Sikhotealinia (Figs A: 3, 7–11, 30–35). In the other Polyphaga, m3 seems to have been lost through its obliteration or perhaps incorporation into “Rr”. The vein termed “recurrent radius” (Fig. 21) usually lacks its base; nevertheless, it is connected basally to rudimentary veins in some Elateriformia (excluding Scirtoidea) and Cucujiformia. Chrysomeloidea display traces of “Rr” bifurcation distal to field B (Fig. A213) more often than the other cucujiform beetles do. Therefore, “Rr” is to be considered a complex vein, RP+MA, not a cross-vein. In elateriform beetles (Fig. A97), frontal and caudal basal remnants of “Rr” are certain to be those of RP and m1 (m1–MA), respectively. What these remnants are in cucujiform beetles largely depends on how field B is to be interpreted. More specifically, it is not improbable that the anterior remnant corresponds to RP–(RP+MA) while the posterior one to m3. I rather adhere to the opposite in believing that m3 was totally reduced in all Polyphaga except Scirtoidea. It was either obliterated or first shifted onto, and then merged into, RP+MA as “Rr” was formed. Forbes (1922) recognized m3 as a true cross-vein, “r–m”. Kukalová-Peck & Lawrence (1993) considered “Rr”of Polyphaga and the RP+MA base of Adephaga, Myxophaga and Archostemata as quite different veins, r3 and RA3+4, respectively. The “radiomedial” vein, “r–m”. This vein braces the leading edge support, which ends in the radial cell, and MP3+4, the latter an integral part of the medial bar. It was Forbes (1922) who already referred to “r–m” as a complex vein. Yet he only recognized (Fig. 2) the posterior component (“r–m” proper) of the vein as a true cross-vein while the anterior component as a section of Rs. This pattern was attributed to Adephaga alone (Forbes, 1922; Balfour-Browne, 1943), whereas the entire vein was considered as r–m for Archostemata and Polyphaga. Kuka-

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

lová-Peck & Lawrence (1993, 2004) define each of the four beetle suborders by a particular pattern of “r–m”. These are: r4 for the Polyphaga, “RA4–r4–RP2” for the Archostemata, “RA4–r4” for the Myxophaga and “RA3+4–RA4–r4–RP1 ” for the Adephaga. The above considerations are certainly wrong, especially those concerning Polyphaga. Apparently, this is due to the radiomedial spur, rms, overlooked in the wings of many Polyphaga. Yet this short and abruptly truncated vein stems from “r–m” at its middle and fails to differ from rms of Adephaga, implying their homology. I consider “r–m” as a jointed vein originally composed of the following veins or veinal sections: (RP+MA)–(RP3+4+MA)–mp1 (Adephaga, Myxophaga, Fig. 17). Archostemata, numerous Adephaga and also probably Polyphaga show the same or perhaps a slightly derived pattern, because MP3+4 is partly fused to mp1 just distal to the oblong cell and thus shifted onto “r–m”. The anterior component of “r–m”, RP+MA, was reduced, being merged (together with the RP1+2 base) into the rc posterior border. This character seems to be a synapomorphy of the Polyphaga (Figs 20 and 21). Apical branches of RP and M. Initially, veinal branches of RP and M seem to have been at least four in number (Fig. 16). Yet four veins occur in no beetle wings but those of a few Hydrophilidae and Histeridae, in which these “veins” are clearly of secondary origin. It is these numerous “veins” that appear to have provoked Forbes (1922) to include no less than five apical branches of RP in the venational groundplan of the beetle hind wing (Fig. 2). In Archostemata, Myxophaga and Adephaga, two distinct apical branches, RP1+2 and MP3+4, do occur. However, these were already modified into weaker (Archostemata) or stronger (Adephaga) flat sclerotized strips, the wing apex having begun to roll during folding. From this, one more longitudinal vein was reduced to its truncated base, rms. This is characteristic of numerous Adephaga (Fig. A8), Chrysomeloidea and some Tenebrionoidea (Stenotrachelidae), but not well-developed, albeit traceable, in Scirtidae, some Curculionoidea (Figs A: 216, 220) and Cucujoidea (Cucujidae, Silvanidae, Passandridae). More or less distinct remnants of rms have also been retained in different representatives of some other taxa of Polyphaga. The Archostemata lacks this vein. A strongly elongated rms of some carabid wings (Cicindelitae) is most likely to be a secondary feature. The radiomedial spur has hitherto been interpreted either as the base of one of RP branches, RP4+5 (Forbes, 1922; Balfour-Browne, 1943), or the MA base (Ward, 1979). I consider rms as the shared base of not three (Fedorenko, 2003) but two veins, RP3+4+MA and MP1+2, partly or completely fused; for convenience, the abbreviation RMP is used below for the product of this fusion. The primary base of MP1+2 occurs only in few Archostemata (e.g. Tetraphalerus: Kukalová-Peck & Lawrence, 1993, fig. 33). Free apical sections of the veins

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involved in RMP are here supposed to have been reduced. Since such have not been found in any extant beetle, they are rather hypothetical than real structures. An answer the question why rms has been formed may concern an improved wing folding apparatus in the course of earlier beetle evolution. In particular, field B changed its configuration from the beetle protowing to the wing of Polyphaga. This change was unidirectional while deviating a little from the general pathway. This should have led to a considerably different orientation of the veins around this field already at the stage of caraboid wing type. More specifically, the base of RP3+4+MA and MP1+2 had to drift together to merge at least into a short shared section. The veins were most likely to approach each other stepwise along the in-between lying cross-vein m4 until they fused distal to field B. This newly formed brace seems to have localized field B and thus reduced its negative effects on the adjacent veins. Besides the radial (rsp) and radiomedial (rms) spurs, there is only one vein, MP3+4, lying in the apical membrane of polyphagan wings. In numerous Polyphaga, this vein1 is associated with sclerotized strips and patches in a highly characteristic pattern. All or only some of these sclerotizations may be secondary structures. Yet the pattern they form is so stable in shape and relative position that they can be supposed to represent rudimentary veins. As underlying the reconstructed wing groundplan of Coleoptera, the wing type of Megaloptera includes a supination line between RP1+2 and RP3+4+MA (Fig. 13). In position, this furrow closely resembles the longitudinal axial fold, la, of the beetle wing, suggesting the fold having derived from the furrow. If so, then the beetle homologues of RP1+2 and RP3+4+MA are to be situated frontal and caudal to la, respectively. Most similar to weakened veins, in both shape and position, are sclerotized strips of some Tenebrionoidea, especially Mordellidae (Figs A134–136). In particular, a vein starts immediately from rsp, with its two apical branches definable as RP1 and RP2. Just behind the fold la lies RMP connected to the RP2 base and MP3+4 by cross-veins rp1 and mp2, respectively. Finally, what could have been homologous to the free apical section of CuA1 grows away from MP3+4 caudad, implying also the CuA1 basal section reduced through complete obliteration or fusion to MP3+4 and the veins proximal to it. This helps to reveal homologues to all the veins of the groundplan. Yet the model being tentative rather than evident prevents me from designating all above structures but MP3+4 as veins. They seem better to be termed sclerotization 1

Unlike sclerotized strips which are flat or concave in cross-section, the vein involved is usually convex. This feature and the position criterion combined allow discriminating between the vein and the sclerotizations with a fair degree of certainty.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

patches, or sclerotizations, of the apical membrane (Figs 4 and 37). Among them, the anterobasal sclerotization (abs) corresponds to RP1 and/or the RP1+2 base, the postcosto-apical sclerotization (pcas) to the distal part of RP2 (or of RP1+2, if the vein was unbranched), the central (cs) and medio-apical sclerotizations (mas) to RMP, the postero-apical sclerotization (pas) to the distal part of CuA1 in the wings of Cucujiformia. The anteromedial sclerotization develops on each side of “r–m” on the basis of a reducing rms. This also involves a secondary base of MP3+4 and probably a remnant of the MP1+2 base as well. The vein MP3+4 is here considered as primitively lying far behind the longitudinal axial fold, la, in polyphagan wings. The vein running close to la is a derived condition resulting from a stepwise drift of the vein forward in a series of successive stages (Fedorenko, 2004a). In the course of this shift, mas usually undergoes reduction. Conversely, a well-developed or strengthened mas/RMP concurs with MP3+4 either reduced partly (A: 93, 96) to completely (A170–171)) or substituted for the cubital spur, CuA2 (Staphyliniformia). The anterior cubitus, CuA, is present in beetles as a more (Adephaga, Myxophaga, Polyphaga) or less (Archostemata) strong longitudinal vein, the cubital bar, this being always complex due to partial fusion between CuA and CuP. This fusion zone either lies between the base and the apical part of CuA (Adephaga) or also involves the CuA base (Archostemata, Polyphaga). Just proximal to the oblong cell, the cubital bar is originally almost interrupted (Archostemata; Adephaga; Eucinetidae, Polyphaga). This cubital break is present where the corners of fields A and G meet, thus forming the cubital pivot (cp) on which the area W rotates basad during folding. As a result, CuA bends angle-wise. This cubital joint (cuj) seems to be a protofeature of Recent Coleoptera while a weak cubital bending zone (cubz), i.e. the smoothed, non-angular bend of an uninterrupted CuA is to be considered as a derived condition of Polyphaga but Eucinetidae. The anterior branch of CuA, CuA1, rises from the oblong cell (o) while forming the distal or posterodistal border of the cell. CuA1 remains free in Archostemata, some Myxophaga, e.g. Hintonia, Claudiella (Kukalová-Peck & Lawrence, 1993, figs 24 and 25) and Adephaga. Distal to o, CuA1 often (some Myxophaga and Adephaga) approaches MP3+4 and either shifts onto this vein as merging with cross-vein m–cu4 and the MP3+4 base (Sphaerius, Spaeriusidae; Ytu, Torridincolidae: Kukalová-Peck & Lawrence, 1993, figs 27 and 23; Hydroporinae, Dytiscidae) or loses its base (some Carabidae and Dytiscidae). In Polyphaga, CuA1 seems to be merged into MP3+4 at least medially. Its initially quite free base (Fig. A37) could have been fused with MP3+4 and the veins proximal to it in most Staphyliniformia or obliterated in the other Polyphaga, occasionally reverting to its short and spur-like remnant starting from the mch (some Cleroidea). What happened to the apical part of CuA1 remains unclear,

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as it was absent from all polyphagan wings studied. It was either merged into MP3+4 or desclerotized, or transformed into pas (Fig. 21). The posterior branch of CuA, CuA2, is a direct extension of CuA apicad, for which reason it is also termed the cubital spur. This vein is of special position in the wing as lying between two strong deformation structures converging at the CuA2 apex. Among them, the principal fold (hw) and the claval furrow, together with field G, evolved in two ways as field H expanded basad. Following the first pathway, fold hw pushed CuA2 basad until it was perpendicular to the wing margin (Fig. A151). In the second pathway, the fold intersected the spur, leaving it either movable during folding or reduced distal to the fold. In Staphyliniformia, except for Hydrophilidae s.l., MP3+4(+CuA1) appears to have substituted for CuA2, resulting from the latter vein’s reduction. CuA2 merged into MP3+4 seems less likely, since the two veins are originally separated at the base by fold hw (e.g. Fig. A39). The oblong cell, or 4m–cu, is an integral part of caraboid venation (Archostemata, most of Adephaga; Calyptomerus, Scirtoidea). When in a plesiomorphic condition, the cell is comparatively large and fairly long (Figs A: 1–11, 13, 17–18, 28–29). In Adephaga, at least Geadephaga, the cell clearly tends to be reduced. It becomes increasingly short and cuneiform (Figs 54; A: 15, 16, 19, 20, 23–27) until reduced (Figs A: 12, 21, 22). The cell is absent (reduced) from the other Polyphaga but Sikhotealinia (Fig. A30). The posterior cubitus, CuP. This vein is always partly reduced in Coleoptera. It lacks its base and often also the apical section, except for Archostemata or some Adephaga (Figs A: 28, 29, 14, 19, 20). In these latter groups, CuP takes off from CuA far distal to the arculus. This pattern is surely derived because it sharply contrasts with what other Neoptera show, Endopterygota in particular. Therefore, the first fork of Cu is to be sought for proximal to the arculus. The basal transverse brace between CuA and superficially 1st anal vein accounts for how the fork of Cu “migrates” apicad. Kukalová-Peck & Lawrence (1993) consider this brace as an “arculus”, m–cua cross-vein, interrupted by a “cubitoanal fold”. Forbes (1922) accepted the brace as a jointed vein in which the anterior and posterior components were the base of “1A” starting from CuA and a cross-vein, the anal arculus (anarc), respectively. The entire brace is designated below as the complex anal arculus, anarc.c. The anarc is homologous in all Coleoptera (Figs 17, 18, 20, 21) while the anterior component of anarc.c. is of different nature in Adephaga, on the one hand, and Archostemata, on the other. Adephaga may serve as an example of how anarc.c. could have been formed. In Adephaga, CuP merged into CuA medially where a cross-vein cu1 could have been situated. Cu was thus supplied with a new branchpoint considerably approaching cu2. The new, secondary base

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

of CuP has persisted only in a few primitive carabids (Figs A: 14, 19, 20). In the remaining Coleoptera, it was reduced either completely (Figs A1–11, etc.) or down to a short remnant, Cur, just proximal to cu2 (Figs A: 12, 15, 16); in both these cases, the respective tracheal stem has often survived where the vein passed until obliterated. The primary base of CuP underwent modification as well. It became desclerotized in its proximal, lengthwise section while transformed into a cross-vein apically, this being the anterior component of anarc.c. As a strong vein, the proximal section has persisted only in certain Dytiscinae (Figs 27 and A8), much less so in some Carabidae (Fig. A20). In the other Adephaga, this veinal section is barely visible, if any. In Archostemata, CuP grows away from CuA proximal to anarc (Fig. A28). This pattern is very likely to have resulted from the CuP primary base merged into CuA up to cu1 or over a little longer extent. This could happen due to a somewhat different relative position of cross-veins as compared with that in Adephaga, e.g. cu1 lying proximal to cu–a1. The Polyphaga shows a pattern which seems to be very close to and derivable from the previous one: there is no secondary base of CuP while anarc is reduced to a short baseless remnant on the anterior anal vein. This remnant is rather long only in primitive Polyphaga (Figs A: 31, 84–85, 110, 134–137), but lost or hardly traceable in the rest. Certain Polyphaga retain or, most likely, secondarily revert to a more or less groundplan pattern composed of the almost meeting CuP secondary base, Cur and anarc (Fig. A86). Apparently, the reversion is due to a considerable increase in body size. Distal to anarc, CuP remains free in such beetles as Archostemata, Rhysodidae, some Carabidae, numerous Elateroidea and Derodontidae (Figs A: 12, 14, 15, 19, 20, 23, 24, 28, 29, 83–87, 107, etc.). In the other Coleoptera, CuP first fuses medially with the anteriormost anal vein, AA1+2. The latter vein first shifts onto CuP, resulting from cu–a2 reduced in between, with an emerging longer or shorter AA1+2+CuP. Veins AA3a', CuP+AA1+2 and the secondary base of AA1+2 in the role of cu–a2 then repeat this evolutionary scenario. In the course of these alterations, the CuP free parts tend to be strongly reduced. This largely concerns the apical section of the vein. It persists in Adephaga, Myxophaga and some Polyphaga, including certain Elateriformia, some Bostrichoidea, Cucujoidea, and a few, predominantly the most primitive members of Chrysomeloidea (Cerambycidae), Curculionoidea (Belidae), Tenebrionoidea (Colydiinae, Zopheridae; Histanocerus, Pterogeniidae) and probably also Cleroidea. The other beetles appear to have lost this CuP section, which conclusion holds true at least for those beetle groups that are defined by the apical veinal branches reduced in number in the clavus. Perhaps Scirtoidea and

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Haplogastra can be referred to as the only exceptions to the rule due to some obscure evidence of CuP or AA3a reduction. Proximal to cu–a2, CuP often survives as a short baseless vein (Figs 20 and 21) here termed the recurrent [posterior] cubitus (Cur), by the analogy with the “recurrent radius” (“Rr”) or the recurrent media (Mr). When Cur is reduced, cu2 becomes a new, tertiary CuP base (Figs A: 73, 74, 87–90, etc.). Under the effect of field G, CuP often detaches a very short proximal fragment associated with cu2 (Figs A: 202, 214, 217). Reduction of the fragment results in CuP and CuA widely separated (Figs A: 225–231, 206–209, etc.). The anal veins. Homologization of the anal veins in Pterygota requires an adequate assessment of how the anals relate to one another, as well as to the cubitus, the claval furrow and what has been termed the jugal, anal and vannal folds. These deformation lines, especially the latter two, have hitherto been interpreted very differently. Thus, it is they that pose the greatest difficulties for identification. A cubito-anal brace was generally recognized as an integral part of all pterygote wings (Kukalová-Peck & Lawrence, 1993). This brace was considered as a veinal one in Neoptera as being formed by Cu or CuP fused to the first anal vein or its anterior branch (Lawrence et al., 1991; Kukalová-Peck & Lawrence, 1993). More recently, however, either this pattern was attributed to Endopterygota alone, with the first anal vein designated as AA3+4 (Haas & Kukalová-Peck, 2001), or AA1+2 was homologized with the first anal vein in the Endopterygota (Kukalová-Peck & Lawrence, 2004). Both AA1+2 reduced and the anal fold substituted for the claval furrow in the hind wings of Endopterygota seem to be ill-grounded. These considerations could have been true if the anal fold were homologous in all Neoptera, being incapable of migrating forward or backward in the course of morpho-functional alterations. Hence, I count the anal veins starting with AA1+2. Other assumptions I proceed from are as follows. The claval furrow as the boundary line between the remigium and clavus of beetle wings originally lies between CuP and A. The jugal fold (jf) is recognized as the only general fold that separates off the jugal lobe from the remigium plus clavus. This convex fold primitively occurs in both wing pairs of Neoptera as an immediate extension of the basal fold (bf), which subdivides the medial plate, when developed, into pmp and dmp. At the wing base, jf passes between 2nd (AA3+4) and 3rd (AP1+2) anal veins. If the anal fold, which is often identified with the vannal fold, is not a heterogeneous structure, then it is reduced totally or probably down to a weak fold that sometimes occurs behind the AA1+2 base in Endopterygota. The anals are here supposed to be primitively not less than five in number in the hind wing of Endopterygota. Among them, the first three, AA1+2, AA3+4

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

and AP1+2, lie before the jugal fold, whereas the other two, AP3 and AP4, as well as the immediate base of AP1+2, run behind the fold. In Coleoptera and some Megaloptera, the latter three veins seem to be more closely associated with each other than with the former two which were also termed the postcubitus, PCu (Lameere, 1923; Snodgrass, 1935), or the plical vein, P, and the empusal vein, E (Hamilton, 1972a, b). The subdivision of the anals into two sectors, AA and AP, I follow here reflects nothing else but closer interrelations between some veins as compared to the others. The veins of the jugal lobe remained free in the course of evolution while those in the clavus likewise anastomosed one another in Endopterygota. These fusion zones appear to have stemmed from two adjacent veins merged along a cross-vein, first in between and then apically. 1A (AA1+2) is either an unbranched vein or it gives chiefly two apical branches. Of them, the posterior branch appears to be the anteriormost branch of 2A (AA3+4) shifted onto 1A. 2A bears a few apical branches. It seems possible to restrict these of the wing groundplan of Myrmeleontidea to three or four in number. The first branch shifts onto 1A, thus enclosing a large, anal, loop (al) at the wing base. The second branch either remains free or shifts onto 1A like the first branch, or fuses apically with the branch posterior to it. The third branch chiefly merges with the “anterior branch” of 3A apically. If the fourth branch did exist, it would be reduced afterwards from being fused to 3A throughout its length, except for the very base. This could be homologized with the basalmost cross-vein lying between 2A and 3A in the wings of some Megaloptera (Fig. 24). 3A (AP1+2) looks forking, but this fork has rather emerged from the fusion of an unbranched 3A with a veinal branch lying either anterior or posterior to it. I accept 3A as corresponding to AP1+2 at the very base, and to AA4+AP1+2+AP3a medially, with AA4+AP1+2 and AP3a being the anterior and posterior branches of 3A, respectively. 4A (AP3) takes off from a well-developed, unbranched 5A (AP4) which supports the jugal lobe. Then it extends directly into the posterior veinal branch (AP3b), passing just behind the jugal fold (Mecoptera; Corydalidae, Megaloptera, Fig. 24). The anterior branch of 4A (AP3a) is situated in front of the fold (see above), with its short base transformed into a cross-vein that jf intersects. The base of AP3a has only persisted in Adephaga (Figs 25–27; A1–27) and Corydalidae (Fig. 24). The above anal pattern seems to be shared by Myrmeleontidea (Figs 12–14) or even all Oligoneoptera. Moreover, it closely resembles what some other Pterygota, e.g. Plecoptera (Fig. 22) or extinct Protereisma, Ephemeroptera (Kukalová-Peck, 1983, fig. 3), show. However, this similarity could be assignable to merely functional causes, among them improved mechanical properties of the wing follow-

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ing its trailing area’s consolidation in a particular way. Namely, independent anals weakly associated with one another evolved into a firm mechanic construction of high integrity, with the anal loop serving as its body. In general, the venational groundplan of the beetle wing’s anal region fits in with the above pattern, being especially close to that of Megaloptera. Yet, unlike other Endopterygota, the Coleoptera shows the anal region of a highly derived structure: there is no anal loop, there are two anal veins instead of three in front of the jugal fold, and there are no less than three apical branches of the superficially 1st anal vein in the wing. An attempt to eliminate these disagreements by reconstructing the venational groundplan shared by Megaloptera and Coleoptera (Wallace & Fox, 1975) failed at its starting point, since it was based on the wrong assumption that CuP was reduced in the beetles; thus 1A (PCu) was to be considered as the vein next to CuA. That the first vein in the beetle clavus runs in front of the claval furrow undoubtedly argues this vein to be CuP. Consequently, the reduced vein, if any, was that situated caudal to the claval furrow; hence, this vein could be nothing else but AA1+2. Two following pathways of this reduction seem most probable, either (1) through desclerotization or (2) through shortening the vein basally. The first pathway must result in al open anteriorly while the second in al gradually reducing in size in the course of cell shifting basad. Either way, the resultant patterns should be indistinguishable in appearance while they would contrast in two differently designated veins, anarc and the base of the superficially 1st anal vein. In the former case (Fig. 17), the first vein at the wing base would be AA3+4, with anarc interpreted as a jointed vein composed of cu–a1 anteriorly and of a rudimentary AA1+2 posteriorly. In the latter case (Fig. 16), anarc should be recognized as cu–a1 while the base of the first anal vein as AA1+2+AA3+4. Cross-veins of the clavus and anal cells. There are two cross-veins, anarc (cu– a1) and cu–a2, between CuP and the 1st anal vein in the beetle protowing (Fig. 1), as well as in the beetle wings of primitive structure. Forbes (1922) and Ponomarenko (1972) considered these veins as true along with the other cross-veins in the clavus of Recent Coleoptera. Forbes also specified that the vein enclosing the first anal cell basally could only be the base of the 4th, posteriormost branch of 1A (“2A”). Conversely, Wallace & Fox (1975, 1980) treated all transverse braces in the clavus as anastomoses of longitudinal veins. Kukalová-Peck & Lawrence (1993) followed this, but adapted it to their own venational nomenclature. They regarded the veins enclosing the anal cells distally as free bases of two posterior branches of “CuA”, i.e. “CuA2” (AA3a'') and “CuA3+4” (AA3b), both fused with “AA1+2” (AA4+AP1+2) apically in succession. The basal brace between the 1st (“Cu”) and 2nd (“AA”) anal veins was recognized as “BCuP” while

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“CuP” proper as an obliterated vein in all beetle wings except for certain extant Coleoptera (some Hydrophiloidea, Scirtoidea and Scarabaeoidea) which these authors believed to have retained a short basal section of “CuP”. Both “BCuP” and “BCuP–CuP” are homologized here with one and the same, albeit differently expressed, structure here supposed to be a remnant of the posteriormost branch (AA4) of the 1st anal vein. In general, I agree with this, considering the anal cross-veins as free bases of the longitudinal veins AA3b and AA3a". These enclosed the first (1a) and second (2a, or cuneal) anal cells distally, having been fused distally with the vein AA4+AP1+2 caudal to them (for convenience purposes, the product of fusion of these veins is here abbreviated to AAP). 1a is very likely to have already existed in beetle ancestors. The presence of the two anal cells is a protofeature of all extant and also probably of most of the extinct Coleoptera. Both 1a and, especially, 2a tend to be strongly reduced in the course of beetle evolution. 2a disappears first, albeit in different ways. More often, a totally reduced 2a results from merged veins it is enclosed with. Disintegration of the cell comes out either of its distal (Elateroidea, some Buprestidae and some Hydrophilidae) or, more rarely, frontal (some Cleridae, Trogossitidae), or caudal border opening up. The vein cu–a2 is here accepted as a true cross-vein. This follows from independently tracheated CuP, on the one hand, and the anals, on the other. Such interrelationships are better traced in larger beetles (e.g. Julodis, Buprestidae) showing a complete veinal set of the clavus. A well-developed cu–a2 is a plesiomorphy of Archostemata, Rhysodidae, some Carabidae and numerous Elateroidea s.l. The remaining Coleoptera lost this vein, AA1+2 having shifted onto CuP. There is a vein-like brace between BCu and 1A in many Polyphaga (Fig. 33). This, however, is only the constituent part of a secondarily structured BCu, albeit strongly resembling in relative position the cross-vein cu–a1 in the hind wing of some Megaloptera (Fig. 24). Apical branches of the 1st anal vein. In the beetle protowing, six apical veins are present in front of the jugal fold (Fig. 1), only four of them reaching the posterior wing margin. The interrelationships of some anal veins in the imprint remain tentative because the anal region is warped, especially at the base: the wing membrane is partly crumpled while the veinal bases are broken and displaced anterobasad. Still, the two anterior apical branches, AA1+2 and AA3a', surely belong to the superficially 1st anal vein. This is likely to have given rise to the next two branches, AA3a" and AA3b, which share the base in the wing basal part, but fail to reach the wing margin. The remaining anals designated as AA4+AP1+2 and AP3a do not conflict with those of extant Coleoptera.

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In fossil (Platycupes, Notocupoides: Ponomarenko, 1969, figs 43 and 48) and some Recent (Fig. A29; Cupes: Forbes, 1922, pl. 31, fig. 12) Cupedidae, four apical branches are present in the clavus. The other Archostemata, e.g. Omma, Tetraphalerus, Distocupes (Kukalová-Peck & Lawrence, 1993, figs 30, 33, 35) and all Adephaga possess only three apical branches. The latter pattern seems to be derived, resulting from the reduction of one branch, most likely AA3a'. This conclusion follows from the anals varying from four to three in number in the wings of some Cupedidae (e.g. Tenomerga), the latter pattern resulting from AA3a' elimination. Four anal veins in the clavus is a groundplan feature of the Polyphaga. Indeed, certain members of Elateridae, Cantharidae, Dermestidae, Cerambycidae and Belidae show these veins increased to five or, seldom, even more in number, besides varying individually. All these patterns seem to be abnormal, resulting from one to a few longitudinal veins split secondarily and chiefly occurring in individual specimens of only some species. This is extremely rare in some of the above groups, but frequent or even regular in some others, among which certain Elateroidea (Elateridae, Cantharidae) and Dermestidae are the most illustrative. Based on the above evidence, the superficially first anal vein is here considered as five-branched. The anterior branch is AA1+2, and the other four belong to AA3+4. These are AA3a', AA3a", AA3b and AA4, the bases of the latter three veins being transformed into cross-veins enclosing both 1a and 2a. In Recent Coleoptera, the bases of the AA1+2 apical section, AA3a' and AA3a", are always situated distal, while the AA4 base lies proximal, to anarc. AA3b grows away from the shared veinal stem either proximal (Archostemata) or distal (Adephaga, most of Polyphaga), or level to (Elateridae, Polyphaga) anarc. The zone of fusion between AA1+2 and the next vein (AA3–AA3a–) varies in length. It is either longer in Polyphaga and some Archostemata (Fig. A28), in which AA1+2 is also fused with the AA3a' base, or shorter when a free shared base of AA3a' and AA3a" is observed. This base seems to be of different origins, supposedly primary in Archostemata and Sikhotealinia (AA3a, Figs A: 29, 30) or secondary in the remaining Coleoptera (Figs A: 73, 110). The following veins belong to AP only. A “forked” AP1+2 passes before the jugal fold, whereas its extreme base, as well as veins AP3 and AP4, lies behind the fold. The vein AP3 has often been overlooked. This has probably happened because the vein is obliterated or indistinct in most of the Coleoptera. Yet Scirtoidea and Adephaga, especially Gyrinidae, show this vein to be conspicuous, albeit ranging from well-developed to very short. The vein’s base is very close to the AP1+2 and AP4 bases, but the order of tracheation of all these veins in Adephaga (Amphizoa; Dytiscidae; Calosoma, Carabidae) argues AP3 to be so specified. Just

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distal to its base, AP3 is braced with AP1+2 by a short cross-vein considerably varying in orientation. I am inclined to treating this brace as conformable to a free base of the longitudinal vein AP3a, this being the anterior branch of AP3; the free apical section of AP3a is thus the “posterior branch” of AP1+2. In my opinion, the following two arguments can be put forth in support of the above treatment of AP3. Among them, the first is that AP1+2+AP3a is often subdivided into two parts lengthwise, with the posterior part superimposed on the anterior one. The second reason is the great similarity between Adephaga and some Corydalidae in the venation of the wing region involved (cf. Figs 24 and 25–27). The vein AP4 has been considered to be primitively either two-branched (Forbes, 1922, 1926; Wallace & Fox, 1975, 1980; Kukalová-Peck & Lawrence, 1993) or unbranched (Ponomarenko, 1972; Ward, 1979). The latter character occurs in most beetles, but Archostemata and some Carabidae, Dytiscidae, Dascillidae, Scirtoidea and Staphylinoidea (Agyrtidae, Leiodidae) show structures which might be identified as apical veinal branches. The nature of those structures is obscured by AP4 being closely associated with the axial cord (ac). When best expressed, ac rims the posterobasal wing margin and disappears just distal to the apex of AP4 (or what could be recognized as its posterior branch). This cord is present in some Adephaga (Gyrinidae, Trachypachidae, some Carabidae and Dytiscoidea). It is also more or less distinct in Cupedidae and some Scirtidae (Figs A: 32, 34), but lost in the other beetles. A tendency towards a reduced ac is well-traced within Adephaga. It is realized in two different ways or perhaps their combination. Following the first pathway, the cord becomes increasingly attenuated and then obliterated. In the second pathway, ac grows progressively short basad, drawing the vein in its wake. As a result, the vein bends more and more (Figs A: 14, 15), forming a smooth loop. This often becomes internal, since ac is detached from the posterobasal wing margin (Figs A: 20, 21). A two-branched AP4 or at least traces of this pattern are only combined with a well-developed cord, but never with a totally reduced ac (Figs A: 4, 5, 17, 23, 24, 26, 27). When ac is well-developed, the following main patterns can be revealed: (1) AP4 is long, unbranched, apically meeting a conspicuous to rudimentary ac, and not forking (Figs A: 1, 3, 6–10); more seldom, ac and AP4 are somewhat shortened (Figs A: 2, 14, 15, 18); (2) AP4 is well-developed, ranging from long to shortened, with a spur-like, short to nearly indistinct “anterior branch” which runs far away from the wing margin; the “posterior branch” varies between short and long (Figs A: 13, 16, 19, 25; Broscini); (3) the same but for the “anterior branch” long (Fig. A22). At least two hypotheses can be put forth to account for the above patterns, as well as those displayed by Archostemata and some primitive Polyphaga. According to the first, AP4 is primitively a two-branched vein. If so, both branches

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of AP4 have only persisted in Archostemata, as well as in certain basal Carabidae (Fig. A22) and Polyphaga, Scirtidae (Fig. A34) and Dascillidae (Fig. A100). The remaining Adephaga and Polyphaga have lost the anterior or posterior branch, respectively. As it follows from the opposite hypothesis I rather adhere to, AP4 “forks” since ac becomes detached from the wing margin; therefore, this “fork” is actually the junction of ac and the apex of the originally unbranched vein (Fig. 36). Hence, the “anterior branch” of AP4 is a secondary structure homologous either to the ac

g

f

a

b

e

c

d

h

Figure 36. Evolution of vein AP4 in association with the axial cord in Adephaga; a–h, morphogenetic stages. Arrows show directions of morphogenesis.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

section lying distal to the AP4 apex or to a secondarily elongated apical section of AP4, or to the product of fusion between the apical section of AP4 and ac. There often are one or two sclerotized strips caudal to AP4, which are sometimes (e.g. Kukalová-Peck & Lawrence, 1993) termed jugal veins. These strips are always deficient of tracheae and most closely resemble wing veins in some Dytiscidae, advanced Carabidae and certain Polyphaga (e.g. Cetoniinae). These strips are here considered either as remnants of ac (sometimes strengthened, perhaps secondarily) or novelties, thus being designated as jugal (js) and postjugal (pjs) sclerotizations. Complex supporting structures. The radial bar (rb) (Kukalová-Peck & Lawrence, 1993) is characteristic of the beetle wing. This supporting axis is composed of ScP and R–RA, tightly contiguous or adnate between the subcostal window (scw) and the pterostigma. In the Coleoptera, except for Archostemata and Scirtoidea, C+ScA seems to have been reduced or also incorporated in rb, thus making it the costal bar (cb). This double or triple structure seems to have emerged from the evolution of the wing folding apparatus. Because the costal margin of the beetle wing originally bends smoothly and rather strongly just anterior to the anterior corner of field B, a single axial bar seems to be an optimal structure to increase the deflection angle, as well as to prevent the leading edge support from damage. Very likely, the formation of rb began between the RP base and r1 where R–RA deformed maximally, and it was not until this had taken place that the fusion zone between the rb constituent parts spread basad. The boundary between the rb integrants is well-visible in Archostemata and Adephaga, yet not so well in most of Polyphaga. A broadened ScP constitutes the body of rb in Adephaga, whereas an incrassate anterior wall of R–RA greatly contributes to cb width in most of Polyphaga. C+ScA having been reduced or merged in cb distal to cw in the bulk of the Polyphaga, cb and rb coincided. At last, cb being more or less narrowly desclerotized along the costal margin in numerous Polyphaga often produces the illusion that rb and a desclerotized C+ScA combined are present instead of cb. Like CuA, cb/rb is supplied with devices of two kinds to deflect the wing apex during folding. These are either extending deflection zones, or bending zones (Schneider, 1978; Haas, 1998; Haas et al., 2000; Beutel & Haas, 2000; Kukalová-Peck & Lawrence, 2004), or joints. Termed also springs (Kukalová-Peck & Lawrence, 1993), the former structures serve for smoothly deflecting the wing apex. The joint is developed to deflect a vein angle-wise where a pivot occurs that abuts on it. During folding either the costal bending zone (cbz) or the costal joint (cj) is developed at the proximal costal pivot

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(cpp) formed by the anterior corner of field B. When strong, cbz is densely transversely corrugated throughout the cb length to provide it with additional flexibility. This crimping is sure to be a derived condition, being an unambiguous homoplasy of Adephaga and some Staphyliniformia (Hydrophilidae, Scarabaeidae). The arculus (arc first and arc.c. after) forms the pivot on which R–rb/cb and CuA rotate, drawing them closer/apart during wing folding/unfolding. The arculus is short and wide in Adephaga. Numerous Polyphaga, especially Cucujoidea, show a considerably longer arc.c. This appears to serve also as a torsion pivot or its part in the wings which strongly supinate along the remigial furrow; the latter coincides with an extended fold cq in case the “serricorn” folding pattern is well-developed. The carpal cell (cc) is the integral part of a primitive, caraboid wing-venation pattern; so a normally developed cc is present only in Archostemata, Adephaga and some Scirtoidea. It was formed to support the central region of the wing during the early beetle evolution. The cell’s irregular shape, coupled with veinal remnants inside, is evidence of the cell being of high complexity. Four primary cells, 3m, 4m, 5m and 1mp, were involved in cc, the borders having been obliterated in between. The least derived is cc of Cupedidae, Archostemata, as it retains these or those rudimentary veins of the primary set (m2, m3, MP1+2 base) inside and the internal border lying far proximal to field B. A general trend of further cc evolution was to localize field B that strongly affected the central region of the wing during folding. As a result, the veinal framing of the cell was drawn closer to the field’s folds and often also to the apical folding sector E–X (i.e. fields distal to B), the latter almost extruded distal to the cell (Adephaga). In the course of this alteration, the veins inside cc were obliterated or evolved into sclerotization patches to stiffen the wing membrane inside (m2) and distal (m3) to field B (Figs 34 and 35). The radiomedial (rml) and mediocubital (mcl) loops are terms used for two basal regions of the remigium, both delimited by three strong longitudinal veins as follows: R–RP (the radial bar), M–MP (the medial bar) and CuA (the cubital bar). The distal borders of these loops are the vein m1–MA and cross-vein m– cu3, respectively. Both rml and mcl are integral parts of a full, caraboid venation type (Adephaga, Archostemata). As this evolved into the cantharoid type, rml and mcl incorporated cc or the oblong cell, respectively. The loops then disintegrated internally while mcl was modified stepwise into the mediocubital hook (mch) as M–MP shortened gradually from the base, thus evolving into a Mr (Polyphaga).

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Secondary supporting structures These wing structures are represented by sclerotization patches and secondary “veins”. They either substituted for veins as primary supporting elements or developed in the wing regions originally deficient in veins. The sclerotizations are of different origin. Some of them derive from rudimentary veins while the others are novelties or both. Both secondary veins and sclerotizations strongly vary in appearance. All of these structures are best developed in Polyphaga, most of them being associated in a very characteristic pattern. Conversely, Adephaga and Archostemata lack secondary veins, with sclerotizations being few and weak. These are certain to conform to rudimentary veins m2, m3, the MA basal section and the CuA2 base, therefore requiring no special terms. Only a small postcubital sclerotization (pcs) inside field G and a surely secondary jugal sclerotization (js) are exceptions. In addition, pcs could have emerged from a rudimentary cu3 in Adephaga, but otherwise in Cupedidae (cf. Figs A4 and A28). Some other secondary membrane sclerotizations serve for deformation lines’ localization, such as the basal section of the claval furrow (Figs A: 5, 6, 9–12), the jugal fold (Figs A: 5, 9), the fold bp (Figs A: 5–7, 13, 25, etc.), the field A (Figs A6–11), etc. Sclerotizations of polyphagan wings (Figs 4 and 37) The depicted pattern is composed of a few sclerotizations associated with both one another and the vein MP3+4. They occupy the apical membrane and slightly penetrate into the wing’s basal part along field C. Among the sclerotizations, the anteromedian (ams), anterobasal (abs) and central (cs) ones support the fields C (or its distal part), D and S, respectively. A short, transversely directed antero-apical sclerotization (aas) extended into a more or less lengthwise postcosto-apical sclerotization (pcas) performs the same function in the anterior part of the apical membrane within field E (+R). The posterior part of the apical membrane within fields H and X is supported by a transverse postero-apical sclerotization (pas) and a longitudinal strip of medio-apical sclerotization (mas). All these sclerotizations, perhaps except only pas, may be homologous to veins (see above). The assemblage aas–pcas is strongly liable to change, with its shape and orientation depending on many wing characteristics, among which the length of the wing apical membrane, the orientation of field D, the presence of a closed field R, etc. can be delimited. More often, aas–pcas is modified into a more or less lengthwise strip arched forward which comes out of a reduced pcas base. A transverse strip aas–aas' resulting from aas extending forward into aas' is as frequent as the previous modification. Concerning the latter two patterns, as well

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as some others, certain of their constituent parts are here strongly supposed to be of different origins in various beetle taxa. For instance, what is designated as aas' on one wing may really conform to cas or pcas in another, and vice versa. The postradial sclerotization (prs) is the most constant element of polyphagan wings. It supports the wing membrane between R–RA and fields B and A or B and C. Throughout its length, prs lies close to R, with a narrow membranous zone in between. When rather wide at its middle, prs can be either evenly sclerotized or strengthened up to vein-like along its anterior margin; prs is the most strongly broadened apicad in Nosodendridae, Anobiidae and some Bostrichidae. The other sclerotizations of the apical membrane are certainly secondary and often developed in parallel in different groups of Polyphaga. Among them,

b

c

a

d

e

Figure 37. Evolution of the sclerotization pattern of the apical membrane in Tenebrionoidea, Polyphaga; a–c and a–d–e, successive stages.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

the costo-apical sclerotization (cas) supports the costal wing margin distal to the apical hinge or distal costal pivot (anterior corner of field D). It develops more often as a novelty (Figs A: 36–62, 107, 114–123, 125, 178, 193, 225, 226), but sometimes on the basis of a strengthened frontal part of aas' or pcas, or fused aas' and pcas (Figs A: 81, 92, 93). In many of these cases, cas is transformed into a secondary pterostigma. A much less frequent apical sclerotization (as) supports the very wing apex (Figs A: 92, 121–125, 145, 152, 180, 181). A more or less vein-like jugal sclerotization (js) performs the same function for the membrane region caudal (superficially proximal) to AP4. Either it is detached from the wing margin (Figs A: 100, 126, 138, etc.) or, more rarely, rims it (Figs A: 92, 96, etc.). Much more rarely, a strong postjugal sclerotization (pjs) bracing 3Ax with the very posterobasal wing margin is present caudal to js (Figs 28 and 30). Two small intercubital sclerotizations, the anterior (icsa) and posterior (icsp) ones, can occur on each side of CuA2. Either icsp alone or both sclerotizations combined is a distinction of some Chrysomelidae (Fig. A213), Melyridae (Fig. A236) and most of Curculionoidea (Figs A: 215, 216, 218–224), icsp being in fact the extension of a shortened CuA2. The resultant complex cubital spur, CuA2–icsp, seems to get the best balanced strength properties, such as rigidity and flexibility, to support the wing both in flight and folding. Such a structure of the cubital spur results from a particular folding first because the spur is to bend strongly at its middle or even in a few points. Secondary “veins” are heterogeneous structures of two kinds. In Staphyliniformia, they emerge from a corrugated submarginal wing membrane, as some of its elements, numerous, narrow, dense veinlets, or “ghost” branches, either hypertrophy or merge into a few strong lengthwise strips. These are as rigid as strongly sclerotized because of their flat cross-sections. Except in flight, the “veins” of this kind are involved in a fanwise folding of the apical membrane. In most of the other Polyphaga, strength properties of secondary veins come out not so much of stronger sclerotizations as of being gutter-like in crosssection. “Veins” of this kind are unlikely related to folding. These occur in some Byrrhoidea (Figs A: 96, 97), Nosodendridae, Anobiidae, Cucujoidea, Cleroidea, Chrysomeloidea and Curculionoidea, members of the latter four superfamilies being very similar in secondary “veinal” patterns. A generalized pattern includes two longitudinal “veins” at bottom, both supporting the apical membrane anteriorly. Among them, the anterior (SV1) rises from a sweeping convexity around fold de while the posterior (SV2) emerges from near aas or between aas and mas. Deviations from this pattern are not considerable, being chiefly restricted to the absence of a basal convexity or SV2, or its base. Or else a transverse “vein” (SV0) is observed, one associated with SV1 in a V-shaped figure (Figs A210–212).

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There is only “vein” SV in advanced Bostrichoidea. It is rather similar in position to SV1 of the above pattern (Figs A114–121). Lymexyloidea and Tenebrionoidea are usually deficient in secondary veins, so patterns close to the generalized one are rather exceptions (Fig. A164). It is only sometimes that a few or numerous convex gutters occur (Figs A: 149, 150, 175). What could apparently add to the rigidity of a secondary vein is either a narrow, medial, sclerotized strip on its dorsal surface (Figs A: 213, 215, 217–222) or the wing membrane intensely sclerotized around and, especially, between the “veins” (Figs A210–236), or both. The latter zone is stepwise modified into a narrow sclerotized strip, the tertiary “vein”, TV (Figs A: 219, 223). The TV–SV association gradually evolves into a complex axial support. This is mostly rooflike in cross-section, with TV and a flattened SV1 constituting its posterior and membranous anterior parts, respectively, with SV2 obliterated (Fig. A224). Similar patterns occur in Derodontoidea (Fig. A107). The sub-cubital binding patch (sbp). Termed so after Hammond (1979), this structure was also referred to as pigment fleck (Sharp, 1882), medial fleck (Kukalová-Peck & Lawrence, 1993), tache médio-cubitale ( Jolivet, 1957), katastigma (Heberdey, 1938) or rubbing surface (Balfour-Browne, 1940, 1943). This is mostly a round, elliptic or, more rarely, angulate patch of the wing membrane densely covered with microspicules and so looking like a sclerotization. It always lies caudal to CuA2 and serves for binding the folded wing to the respective binding patch on the undersurface of interlocked elytra. Either the left wingelytron couple of binding patches is independent from the right one or both sbp of the wing pair are bound superimposed on each other to the apicosutural binding patch shared by the elytra. In most beetles, sbp is either lacking or separate (most of Tenebrionoidea, some Cucujoidea and Chrysomelidae; Figs A: 130, 132, 133, 140, 143–148, 185, 186, 191, 192, 211, etc.). Conversely, in some Adephaga (Figs A: 5–6, 9–10), Cucujoidea (Figs A: 188, 189, 200, 206) and certain Tenebrionoidea (Figs A: 153, 154, 174), sbp is closely associated with the apical section of the clavus’ anterior vein in adjoining it from behind (Adephaga) or being penetrated by the vein (Polyphaga). To order the above patterns in transformation series one should answer the following questions: (1) Is the sbp-vein association primary or not? (2) What are the veins with which sbp is associated primarily and secondarily? (3) Is sbp a synapomorphy or homoplasy? Given the sbp function, the hypothesis seems preferable that sbp could have emerged from or in close association with a vein: the vein as a reliable brace between sbp and wing support would prevent the folded wing from its being shifted spontaneously. This hypothesis might mainly be accepted for Adephaga

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

and Tenebrionoidea. On the contrary, the combination of a well-developed separate sbp and a full venation of the clavus in such primitive cucujoids as Protocucujidae or Sphindidae points to a membrane origin of sbp. An answer the second question is largely conventional because the clavus’ apical veinal branches considerably vary in number. When associated with sbp, a vein is here considered no other but CuP unless otherwise stated. This association is recognized as primary only for Adephaga and Tenebrionoidea. In all other cases (Cucujoidea), it is accepted as secondary, derived from the occupation of CuP by sbp. Homoplasy is certain for Adephaga and Polyphaga, maybe also for Tenebrionoidea, Chrysomeloidea (Chrysomelidae, Orsodacnidae), Cucujoidea and some families within the latter one or two superfamilies. To summarize, the CuP–sbp association is a groundplan feature of Adephaga and Tenebrionoidea. In Cucujoidea, sbp stemmed from the wing membrane and entered a vein (Biphyllidae, Byturidae, Monotomidae, etc.) secondarily. This vein is here designated as CuP, albeit it might be either AA1+2 or CuP+AA1+2. The lack of an sbp is very likely to have resulted from its reduction (Passandridae, Laemophloeidae, Cryptophagidae, Nitidulidae, Brachypteridae, partly Cerylonidae, Coccinellidae and related families). This may also hold true for Helotidae, Phalacridae and Bothrideridae. When a separate sbp is only combined with four apical veinal branches in the clavus (Erotylidae, Languriidae, some Chrysomelidae), the anteriormost veinal branch is recognized as AA1+2 while CuP as reduced. Successive stages of this reduction remain uncertain: CuP could have been either desclerotized or fused to AA1+2 when both were combined with a separate spb, or this reduction followed the detachment of sbp from the CuP–sbp association.

Folding pattern The folding pattern, or fold system, is a structure of high complexity. It integrates elements of two different structural-functional grades or levels (Figs 5 and 6). Separate folds varying both in number and position and not or feebly associated with one another structurally are a lower grade. As a rule, these are peripheral folds entering the wing margin. Closed fields occupying the central regions of the wing are a higher grade. These fields are chiefly triangular in shape and either not adjoin the wing margin or touch it with one corner only. The basalmost and unclosed fields of the apical membrane are of intermediate position in the hierarchy. The jugal fold (jf) among the others is of special importance. As a groundplan feature of Endopterygota it is responsible for folding adducted wings roof-

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wise (Martynov, 1925; Rasnitsyn, 1980b; Brodsky, 1988). Both functionally and structurally, jf is in no way involved in reducing the wing length; therefore it does not cooperate with the other folds in beetle wings (Figs 45–47). Functionally, each fold serves as a hinge for any two wing regions it separates, these being either fields or a field and an area. Principal for the wing is the apical hinge composed of the fold e0 = dq. Each corner of the triangular field operates as a pivot on which the wing regions lying on both sides of the field rotate relative to each other. There are three main pivots in beetle wings, as follows: proximal costal (cpp), distal costal (cpd) and cubital (cp), these corresponding to the anterior corners of fields B and D, and to the posterior corner of field A, respectively. Schematically, the folding of a beetle wing is a base-to-tip kinematic chain of the following elementary steps. Folding starts at the wing base (fields A and B), then it extends over the central part of the wing (fields C, S and D) and terminates at the wing apex (fields H and E–R–X). The internal fields of the remigium, chiefly B–C–S–D, are leading in this process, with those of the clavus (G, F) and apical membrane (R, E, X, H) being driven. The central field group, A–B–C, includes fields of triangular shape which extend along the wing’s longitudinal axis adjoining each other with one corner only; rarely, fields A and B overlap secondarily in Carabidae, some Dytiscidae (Dytiscinae), Cleroidea, Cucujoidea and Tenebrionoidea. Field B, or proximal pivotal field, is of special functional and, consequently, evolutionary importance in transformations of the field having defined numerous modifications in the fields A and C it is associated with. During beetle evolution, field B among the others appeared first, thus having become a starting point for the formation of a folding pattern as a whole. At earlier evolutionary stages, the field was large (Archostemata, Myxophaga, Adephaga) and thence strongly affected the adjacent veins. As a result, a venation pattern characteristic of the Coleoptera was formed. Firstly, the radial bar and then the costal bar were developed, with the costal bending zone (Adephaga) and afterwards the costal joint (Archostemata) being formed at the proximal costal pivot. Secondly, the outer veinal framing of the field became stronger while the veins lying in close contact with the field (m2, m3 and the MP1+2 base) got weak to totally reduced. As the polyphagan folding pattern developed, field B tended to be reduced. The fields S and D in tandem, especially the latter field, played the leading role in this alteration. The field D at first performed the same function as the field B and then took this function over, to a greater part or entirely, from the field B. This happened because field D proved to be of a more favourable position in the wing than field B was. More specifically, lying distal to the basal, supporting part of the remigium, the field D almost in no way troubled the wing support, whereas the

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

field B when well-developed induced numerous deformations, including a strong bending of cb, the latter serving to support the wing leading edge. Within Polyphaga, a large field B occurs only in Scirtoidea (Clambidae excluded), Bostrichoidea and some Cleroidea. In the latter two taxa, it is certain to be secondary as constituting part of a highly specialized folding apparatus, of which a secondarily strengthened costal bending zone is characteristic (Figs A: 113–119, 122, 123, 235, 236). Unlike the field B folds in the wings of Archostemata and Adephaga, those of Polyphaga are often inverted: bq and bw are concave while bp is convex. Accordingly, these are derived and are to belong to a secondary, tertiary, etc. field which can only be termed B for convenience reasons (Fedorenko, 2003). The secondary field is likely to have been developed on the basis of the former field B. It either replaced the field B proper or, more likely, was formed a little distal or proximal to this field, new folds having appeared on one side of the field B while some primary folds having been reduced. Field K, or radial field, is narrow, longitudinal and rudimentary, thence with folds of ambiguous polarity. It occurs in Cupedidae only. Sometimes a field of similar shape and position is observed in Eucinetidae. If this field is a protofeature, its direct influence could account for the absence of a distinct basal part of MA from many beetle wings. Field A, or medial field, is initially fairly large, lying between MP and CuA. A cubital hinge is developed where its posterior corner meets field G (Archostemata, Adephaga, Myxophaga, Polyphaga: Eucinetidae). This field almost always persists even in the wings of derived structure, being somewhat shortened from the apex. As a rule, a strong to complete reduction of field A either follows a reduced field B or results in a narrower mch (some Staphylinoidea, Scarabaeoidea and Histeridae). The combination of a well-developed field A and a rudimentary or missing field B occurs more rarely (some Cucujiformia). In Polyphaga, field A often splits into a few, usually two, daughter fields. Among them, the caudal medial field (Ac) is an immediate successor of A in fold polarity while the folds of the frontal medial field (Af) are inverted. At the next evolutionary stage, both fields are arranged lengthwise, Af following Ac, with the latter field tending to be strongly reduced in size until either confined to the very wing base only or obliterated. This accounts the best for why the field “A” is inverted in numerous representatives of different polyphagan families (e.g. Bostrichoidea, Cleroidea). Fields C (anteromedial field), S (central field) and D (distal pivotal field). All three are only present combined in Polyphaga. In Archostemata and most of Adephaga, fields S and D are absent while field C has no regular external border. Only Carabidae and Trachypachidae possess two fields, Ca and Sa, similar but not homologous to the fields C and S, respectively.

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The field C is almost always present in Polyphaga. Exceptions are only some representatives of Anobiidae, Bostrichidae, Brentidae, Jacobsoniidae and certain members of Melyridae and Tenebrionidae, i.e. beetles with highly specialized folding patterns. In these, fields C, S, D and H fuse with one another in various combinations, sometimes with C totally reduced (Figs A: 118, 119, 166, 224, etc.). While rather small in the groundplan, field C tends to be strongly elongated. When so, it is always combined with fields B and, usually, A being partly to completely reduced. The tendency towards an elongated field C culminates in the field’s proximal corner reaching the arculus. This pattern is likely to have developed in different ways, with the inclusion of field B’s posterior part in the field C being the most frequent (Fig. 38). Before this occurs, field B becomes subdivided into two or three parts, of which the proximalmost becomes lengthwise and involved in a new, complex field C. This thus comes into direct contact

a

b

c

d Figure 38. Evolution of the “clavicorn” folding pattern into the “serricorn” one; a–d, successive stages.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

with field A while the field B gets reduced or “inserted” in the field C. It is in such a way that the “serricorn” folding pattern, as well as some variants of the staphyliniform folding type, has been formed. The field D is usually a closed triangle, with its anterior corner entering the wing costal margin and thus forming the [external] distal costal pivot, cpd(e) (Fig. 39 c). In a more derived condition, the field in question is partly reduced in size, with its anterior corner detached from the wing margin. Only wings with strongly advanced folding patterns (Figs A: 113, 114, 116–119, 123–125, 166, 224, 235) are devoid of this field which has been reduced or merged into adjacent fields. On the contrary, in a number of beetle groups (Scirtoidea; Dascilloidea; Schizopodinae, Buprestoidea; some Elateroidea, Tenebrionoidea and Cucujoidea) the field D is narrowly or widely open along the wing margin. The field D stemmed from field E’s basal part, with fold de formed to separate both. The internal border of the field D, i.e. the fold dq = e0, or the apical hinge, conformed to the internal border of the field E, the latter being a part of the entire apical folding sector (E–X); this, originally, had supposedly been rolled (Archostemata). When well-developed, field D varies considerably in shape, size and orientation of the folds it is enclosed with. These field parameters strongly depend on those of the fields (primarily, C and S) most closely associated with field D, as well as on wing shape and probably also some other wing characters. Hence, the answer the question which particular field D configuration is to be considered as a plesiomorphy of Polyphaga is ambiguous. I suggest this to be the field widely open along the costal margin. This is supported by the field D is widely open in Polyphaga with the least derived structure of the wing as a whole (Scirtoidea) and the most primitive members of some other Polyphaga (Dascilloidea, Buprestidae, Stenotrachelidae, Mordellidae, numerous Elateroidea). When choosing between open and closed fields, I also consider the general trends in the evolution of beetle folding patterns (see below). A functional difference between open and closed fields D is fundamental. A widely open field D in operation gives the minimum reduction of the wing length because its apex hinges only on the folds dq and de while generally retaining a longitudinal orientation. Since closed, the field D becomes a functional analogue to the field B in making the wing apex turn upon the distal costal pivot and thence deflect, not retract basad as above. As an open field D gets closed, the deflexion angle, i.e. that between the wing longitudinal axis and the basal section of fold la in a folded wing, increasingly approximates to 90º. The wing apex folded in such a way either no longer requires further shortening (when the elytra are wide enough) or it can readily be reduced by one to a few couples of oblique folds. Field H, or principal field, always works alongside the apical folding sector E–X, being driven in this association; therefore, secondary folds which almost

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always strongly vary in number and position often intersect this field. The field appears to be primitively tucked flat along a not quite developed, convex fold hw (the principal fold) which passes just distal to the CuA2 apex. It is conceivable that the fold hx as a boundary between the fields H and X either declines or gets fused with fold la, or substitutes for it in most of the Polyphaga. The apical folding sector (E–(R)–X) is the most labile fold association. This is largely due to the particular, apical, position of the sector in the hind wing and, consequently, in the kinematic chain of folding. As a result, the sector’s folds can strongly vary both in number and position not only in different individuals of one species but in the left and right wings of one and the same adult. All this prevents me from an overall homologization of the sector’s folds, yet allowing to discuss the general trends of its evolution. The apical folding sector is absent from the beetle protowing. In folded archostematan wings, it looks like a bilaminar roll spiraled around the fold la. Proximally, the sector is delimited by two, not quite developed folds, e0– and x0+, the former being conformable to the fold dq of Polyphaga. Accordingly, the apical sector begins on where field C’s anterior corner is situated in the wings of more advanced Coleoptera. The wing apex rolling up starts from moving the fold la ventrally and posteriorly, thus making fields E and X concave and convex layers of the roll, respectively. In flattened apical rolls of the wings of most of Adephaga (Haliplidae, Noteridae, Gyrinidae), couples of concave (en) and convex (xn) folds are added to well-developed folds e0 and x0 in the respective fields E and X. Those folds radiate from the fold la towards the antero- and posterodistal wing margins, respectively. To fold the wing apex flat, the folding pattern of Polyphaga was equipped with the field S and the folds dq = e0–, de = e1+ and hx–, all of which differentiated in the basal part of the apical sector. With these integrants being well-developed in all Polyphaga, the wing apex, nevertheless, is rolled in some of them (e.g. Artematopodidae, some Mordellidae and Oedemeridae). In these, rolling starts with fold la moving forwards, not backwards, as in Archostemata or Adephaga. Hence, fields E and X are convex and concave, respectively, in folded wings of these Polyphaga, i.e. they are folded invertedly as compared with the respective fields of Archostemata1. The way in which Polyphaga fold their wing apices is certainly advanced farther than that of Archostemata or Adephaga, and is likely to have derived 1

There are rudiments of the wing apex rolled in some other Polyphaga. For example, Attagenus, Dermestidae, or Campsosternus, Elateridae, show a short roll similar to that of Archostemata. Although the wing apex so folded is most likely derived from that folded flat, it demonstrates high lability of the apical sector.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

from it. In spite of this, one can only hypothesize how this apical folding was achieved. It might have resulted from flattening an archostematan apical roll which spiraled in the reverse direction. If so, the fold e1 should have evolved into the fold de while the convex fold x1 (= sh) co-operating with e1 might have enclosed the field S externally, with fold x2 (= hx) substituting for the fold x0. But the groundplan folding pattern of Polyphaga might have emerged from a never rolled wing apex. If so, it should have derived from new folds developed in the fields E and X, in combination with at least a few reduced primary folds. Thus, the folding pattern of the wing apex of Coleoptera seems to have passed through three successional morphofunctional grades. An upgrade happened each time when a new triangular field or several fields were added to the former fields from the apex. The large and supposedly non-differentiated apical sector of the beetle protowing seems to be most primitive among the others. Wings of Archostemata and Adephaga + Myxophaga are a higher grade in having a well-developed field H and an incipient field C combined. At last, the polyphagan apical folding pattern is the most strongly derived, since it includes the field trio C–S–D or at least the former two fields in tandem. The above interrelationships and evolutionary events can be well illustrated by the fold la: this starts from the distal corner of the field B in the beetle protowing and becomes increasingly short as its proximalmost sections corresponding first to the fold cq and then to the fold sd become incorporated into the fields C and S, respectively. How the fold la evolved within Polyphaga was obscured by a pronounced tendency towards vein MP3+4 a stepwise shift forward in many representatives of the suborder. In the course of this shift, the distal part of vein RMP (mas) was totally or almost obliterated while the primary folds around the vein either migrated or disappeared, including their replacement by secondary folds. This culminated in what a fold lying just frontal to MP3+4 became the longitudinal axial fold. This might have been either la or hx, or a fold of the field X. Because the homology of these folds in different polyphagan wings is far from clear, the terms la and hx are used here for all the wings unless otherwise stated. It follows also that the field H, as well as an expanded X, have persisted somewhat shifted basad as compared with those in the groundplan. Field R, or the third costal field. In the groundplan folding pattern of Polyphaga, the field R is nothing but the field E portion proximal to fold e2. Not until the groundplan evolved into advanced folding patterns, chiefly the “dryopiform”, bostrichoid and melyrid ones, did the field R become the same structural-functional unit as the other triangular fields had been. This happened since a free tip of the fold e2 turned basad and entered the distal costal pivot, this being predominantly external (Fig. 39).

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As the above three folding patterns evolved, the field couple D–R and, consequently, the distal costal pivot (cpd) tended to be increasingly internal. These had concurred with the secondary apical hinge (ahII) until the latter supplanted them. This hinge is a secondary fold connecting cpdi to the wing costal margin. It could be homologized with one of the three folds, if necessary. These are dq when ahII is concave or de or e2 when convex.

a f

b

c

e

d

Figure 39. General trend in the evolution of the folding pattern in Polyphaga; a–f, successive stages; ah, apical hinge; ahII, secondary apical hinge; cpp, proximal costal pivot; cpd, distal costal pivot: virtual (cpdv), external (cpde), doubled (cpdd), internal (cpdi).

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Field G, or intercubital distal field. A well-developed field G (plesiomorphy) is always combined with the cubital pivot (Archostemata, Adephaga, Myxophaga; Eucinetidae, Polyphaga). In the other Polyphaga, the field usually gets partly reduced. Its basal portion adjoining CuP just distal to cu2 dissolves in the wing membrane while secondary folds anterior to the reduced portion build up the remainder. A very narrow field resultant from this lies close to the cubital bar, CuA–CuA2. The proximal corner of the field either declines at the juncture of CuA and cu2 or enters cu2, thus extending into the anterior branch (cf1) of the claval furrow. When so, the field appears to serve as the distal section of the claval furrow rather than the field proper. Sometimes, for example in some Bostrichoidea (Figs A: 113, 115, 119), field G becomes either engrossed or supplied with additional, mostly unstable folds or fields. Field N, or intercubital proximal field, is more or less strongly developed in Cupedidae and Eucinetidae, being reduced totally or down to a fold in the remaining beetles. Because the fold is chiefly concave, it is likely to perform the function of the anterior branch of the claval furrow. It either declines at cu2 (plesiomorphy) or intersects it and adjoins the field G derivative. Field F, or cubitoanal field, is strongly to completely reduced in Coleoptera, except for Archostemata, Eucinetidae and some Adephaga (Figs A: 2–4, 6, 9–11, 18–20), for which reason a well-developed field F seems to be a beetle protofeature. Field J, or jugal field, corresponds to the jugal lobe of Neoptera, thus lying posterior to the jugal fold. The field is almost always well-developed in larger beetles. The smaller the body size, the shorter the hind wings, the smaller the jugal lobe and the deeper the jugal incision. The best-developed jugal incision can almost reach the wing base. Sometimes the jugal lobe is totally reduced. Following the jugal lobe tucked along the jugal fold, portions of the area T and field J, all adjacent to the jugal fold, are often involved in folding the wings with a strongly enlarged anal region (some Carabidae, Dytiscidae, Curculionoidea, etc.). A couple of secondary folds perform this function. These radiate from, but run close to, the jugal fold. A few membrane puckers occurring in veinal forks of the area T often accompany the folding of this narrow wing sector. A feature of most of Polyphaga is a postjugal lobe (pjl), or J2. This very small wing sector lying between the jugal lobe, J or J1, and 3Ax (Figs 5, 31–33) is very likely to have been a novelty resulting from what a couple of folds, pjpr+ and pjd–, was formed. These diverge from near the 3Ax head, one separating J2 from 3Ax, the other from the clavus + jugum. Sometimes a small, secondary, intercalary field Ji is observed inside the field J1.

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EVOLUTION OF THE HIND WING IN COLEOPTERA To understand how the beetle wing evolved as a whole, first one should consider how the integral parts of this whole, i.e. the supporting system, with venation at its bottom, and the folding pattern, developed and contributed to the evolution of the whole wing. The typology of wing venation and folding pattern seems useful to reach the goal, especially when their typologies are compared with each other. Yet the venational typology is generally much less informative than that of folding patterns. When considered regardless of folding, venation patterns form a succession hardly reducible to the caraboid, cantharoid and staphylinoid types, because there are no gaps seen in between, especially the latter two. In contrast, folding patterns can be ordered into a hierarchic system, which much better reflects evolutionary change in the wing folding apparatus. The main folding patterns (folding types) The coleopteran type, or prototype (Fig. 15). This is a rather hypothetic construction, being an integral part of the beetle protowing. Field B very large, triangular, twice intersecting RP+MA; fold bq directly extended into a convex fold hw. Anterior corner of B adjoining RA between RP and r1 and lying equidistant from distal and proximal field corners in longitudinal direction. Posterior border of B (bw) lengthwise, lying close to MP–MP1+2. Fold hw intersecting MP3+4 and CuA1, entering wing margin distal to CuA2 apex. Remaining main elements, especially fields A and G, in an inceptive stage. Wing apex likely to have fan-folded (Fig. 1) along folds radiating from anterior corner of field B and then passing between RP+MA branches. The archostematan type. Field B as above but a little smaller and of a somewhat different orientation. Fields A, G and H well-developed, C incipient, D and S not yet formed. Field H delimited by a convex fold x0 distally. Fold hw lying distal to CuA2. Wing apex (E–X) more or less regularly rolled through folding. Wing costal margin smoothly deflecting at field B’s anterior corner due to a radial bending zone (cbz) in operation.

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A combination of the proximal costal pivot (cpp), the cubital pivot (cp) and no or an indistinct apical hinge (ah) is characteristic. This hypothetical folding type is here recognized as the groundplan of the Recent Coleoptera, which gave rise to at least three derivatives, as follows. The adephagan subtype (Adephaga and Myxophaga, Figs 17; A1–27). A slight modification chiefly defined by a reinforced cbz and fold hw intersecting CuA2 at its base (apomorphies). Wing apex folding variously: either a flattened roll (Figs A: 3–5, 9–11; Sphaerius, Myxophaga) or a crinkled apex (Fig. A12), or apex folding flat more (Fig. A13–27) or less (Figs A: 1–2, 6–8) regularly. Fields Ca and Sa (or Ca alone) either in an incipient stage or, more seldom (Carabidae, Trachypachidae), well-developed. Apical hinge composed of a well-developed fold e0. The schizophoroid subtype (Fig. 19). This reconstruction is based on the folding pattern and wing imprints of extinct schizophoroid archostematans (Schizophoridae, Catiniidae) as described and depicted by Ponomarenko (1969). The main distinction of the subtype is the field B of highly unusual shape and orientation. This is due to the anterior corner of the field situated much proximal to its distal and posterior corners; thence the folds bp, bw and bq look like posterior, distal and anterior ones, respectively. As this pattern formed, the RP base reduced while the RP+MA base was released from being intersected by the field B. The latter, because of all these characters, is either in no way or only marginally involved in the wing’s transverse folding, with this function apparently going over to the apical folding sector E–X. The cupedid subtype (Recent Archostemata, Fig. 18; A: 28, 29) is distinguishable from the archostematan type as groundplan, chiefly because (1) the costal joint substituted for cbz, and (2) the wing apex spiraling in a regular conical roll. The anterior corner of the field B is situated distal to its proximal corner. The fields K and N are also characteristic. The polyphagan type (Fig. 20). Its distinctive features are closed fields C and S, especially when these combined both with each other and with fields D and H, the latter field being delimited distally by fold hx-. The fold hw originally lies distal to CuA2. The wing apex is either folding flat or spiraling in different directions, or both. The apical hinge in the form of the fold dq is well-developed. A reconstructed groundplan will strongly depend on the assessment of the interrelationships between the “clavicorn”, scirtoid and elaterid folding patterns. Among these, the former can be recognized as the groundplan of most of Polyphaga. Yet the scirtoid folding pattern and, especially, its eucinetid variant seems to be much more primitive in having the following plesiomorphies: a large field B (or its derivatives), well-developed fields G and F, and a widely open field D. What is the elaterid folding pattern is uncertain because interca-

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lary fields I (Fig. 6), as well as a rolled wing apex (Fig. A70), can be considered as either apomorphies or plesiomorphies. Based on this evidence, I recognize the groundplan as conformable to the “clavicorn” folding pattern, but for a widely open field D, fairly large fields B and G, a well-developed cubital pivot/joint and probably also the costal joint at the proximal costal pivot. The original way of apical folding is uncertain as it could have been flat or spiral. The scirtoid subtype. This corresponds to the “cyphonid” type among the other two subtypes of Forbes’ “Bostrychiformia” and probably also to his understanding of the groundplan of the latter type. The main distinctions are a widely open field D and both well-developed proximal costal and cubital pivots. All triangular fields are large. This character seems to be plesiomorphous for the fields A, F and G, but may be apomorphous for the field S and a rather short and wide C. There are the field N and probably also K. The wing apex is folded flat. The central folding is highly peculiar due to the following three or at least two fields instead of the single field B initially occurring in this wing region. These are either proximal (Bi), anterior (Ba) and distal (Be) fields combined or Bi is coupled with Be. Among them, Be is certain to have been a novelty, whereas each of the other two fields can be considered either as derived from or, on the contrary, conformable to the field B. It matters little whether the pattern Bi–(Ba)–Be is a synapomorphy of Scirtoidea alone or Polyphaga in general. Yet it started developing since two secondary folds, one concave, the other convex, became the proximal and posterior fold of the field Be, respectively1. As this folding pattern evolved, the field Be was apparently reduced in part or entirely while the field C with which the field Be had shared one corner before extended basad. Of the other fields of the B-group, only one has persisted, either Ba or Bi, or Ba+Bi. As a member of the subtype, the eucinetid folding pattern (Eucinetidae, Fig. A31) seems to be especially close to the groundplan. The scirtid folding pattern (Figs A32–35) is apparently derived in bearing the following apomorphous features: (1) a totally reduced field A and thence a lacking cp, or vice versa, and (2) modified fields F and G. Among the fields of the B-group, either two, Be and Bi (Ba+Bi) (Fig. A33), or only one, Bi (Ba+Bi) (Figs A: 32, 34, 35), have been retained. In the clambid folding pattern (Clambidae), a large triangular field of complex nature plays the leading role in wing folding. The internal, external and posterior borders of the field are very likely to conform to the fold bepr–, the fold line bq–cw–hw+ and the fold gw, respectively. Hence, this complex field 1

The development of these folds could account for the absence of a cross-vein mamp3 and, consequently, an internally open oblong cell in almost all Polyphaga.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

emerged from the inclusion of the area W in the field Be, the fold bep having been reduced in between. Perhaps it is this reduction that enabled Calyptomerus to retain the oblong cell (Kukalová-Peck & Lawrence, 1993, fig. 57). The “diversicorn” folding group (Fig. 39 b, c). Its groundplan is prototypical of Polyphaga but Scirtoidea. Field D is usually closed, triangular, but primitively widely open (Figs A: 130–138, 189); field G is rudimentary due to a reduced cubital pivot. The characteristic of this pattern came out of field B’s function in strong decline as being taken over by field D. Gradual reduction of the field B followed thence, with the apical hinge (ah) functionally substituting for the proximal costal pivot (cpp) first, and the distal costal pivot (cpd) for ah and cpp after; the costal joint, if any, thus reverted to a very weak or indistinct costal bending zone. The “clavicorn” and “serricorn” patterns as members of the group are linked by transitions, sometimes being inseparable as contrasting only in quantitative characters. The former pattern seems to be almost groundplan while the latter is certainly derived. The “clavicorn” subtype. This is characteristic of the wings with a fairly long apical membrane, ca 25–40% of the total wing length. Fields B and A are usually well-developed while C is either not or weakly extended basad (e.g. Figs A: 188, 191, 211). Nothing but a little smaller fields C, S and D, as well as a slightly larger apical folding sector E–X, could only be considered as differences between the present pattern and the “diversicorn” groundplan. The “clavicorn” folding pattern passes across all of the series of Polyphaga, being ancestral to the folding subtypes discussed below, perhaps except for the elateroid one. It is observed in Cucujoidea, Cleroidea, primitive Bostrichoidea (Orphilus, Dermestidae; Endecatomidae, Fig. A120) and all of the Chrysomeloidea (perhaps except for the larger Cerambycidae). Among Elateroidea, only Cerophytidae and some Buprestidae (e.g. Anthaxia) show it. It seems appropriate to regard the salpingid folding pattern (Figs A: 174, 175) as a specialized variant of the present subtype. Except for some Salpingidae and Pterogeniidae, it occurs in certain Silvanidae (Silvanus) and probably also some other beetles. The distinction of the pattern is the combination of a closed field R and a still open field H. The former character is a formal argument for drawing this pattern closer to the “dryopiform” one and for suggesting it to be a link between the “clavicorn” and “dryopiform” patterns. The byrrhoid folding pattern (Figs A: 94, 95, 97) is distinctive in the internal, not double, distal costal pivot. It is present in primitive Byrrhoidea (Callirhipidae, some Ptilodactylidae, Byrrhidae) and gives rise to the “dryopiform” pattern of the remaining byrrhoids (Figs A: 96, 98, 99) but Eulichadidae in which the elaterid folding pattern (Fig. A93) is most likely to have evolved into the byrrhoid one.

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The pseudobostrichoid folding pattern is the most specialized and very rare derivation (some Tenebrionidae; Sphindus, Sphindidae, Fig. A187). It emerges from fields D and C being split up into a few independent triangular fields, resulting in an open field D and the distal costal pivot reduced down to a concave fold dq, the latter serving as the apical hinge. These characters, especially the latter one, add much to the similarity between the pattern involved and the “bostrichoid” one. The “serricorn” subtype (Figs A: 73, 76, 81–82, 88–90, 126, 144, 149, 178, etc.). This subtype is a feature of wings with a considerably shortened apical membrane (up to 12–7% of total wing length). It results from a steady evolutionary tendency towards a basad strongly extended field C, combined with field B (and often also A) partly to completely reduced. Thus, the “serricorn” pattern emerges as a slightly modified “clavicorn” pattern or a reduced variant of the elaterid one. The pattern involved most frequently occurs in Tenebrionoidea and some Elateroidea (Lycidae, Lampyridae, Omethidae, Throscidae, some Eucnemidae and Elateridae), to which certain Dermestidae (Dermestinae) and some Cucujoidea are to be added. It is uncharacteristic both of Cleroidea and Phytophaga. The staphyliniform subtype (Figs A: 36–69, 201) seems to be heterogeneous and poorly differs from the “clavicorn” subtype in the following characters. (1) Fold hw intersects the CuA2 base, resulting in the distal portions of areas V and W involved in field H1. (2) Fields S and D are subequally large and of similar shape; the latter field is somewhat extended along its posterior fold, sd, so that the posterior corner of the field lies clearly distal to the anterior corner. (3) There is a tendency towards a “simplified” folding which shows at an early evolutionary stage. Thus, when the folding groundplan of Polyphaga is in operation, the following folding events take place in succession: the basal longitudinal folding by means of the field C – the central, complex, largely transverse folding through the fields S and D – the apical, complex, longitudinal and transverse folding (fields E–X). In advanced Haplogastra, excluding some Hydrophilidae, this base-to-tip kinematic chain is reduced to two links: the longitudinal folding along the line cq–sd–la is followed by transverse folding through the fields S and D. The following modifications contribute to this process: (a) the fold line la–sd approximates to the straight line, (b) fields D and S become coupled 1

This pattern has been developed in parallel in numerous Coleoptera, including Adephaga + Myxophaga, Eucinetidae, Haplogastra, some Byrrhoidea, certain Dermestidae, Derodontidae, Nosodendridae, Malachiinae, some Cucujoidea (Monotomidae, Nitidulidae, Cryptophagidae, etc.), some of Tenebrionoidea (e.g. Othniinae, some Anthicidae) and numerous Curculionoidea.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

and thence congruent, (c) secondary folds radiating from the central region of the wing appear between apical veinal branches to make a fan-folding possible. Corrugated submarginal parts of the wing membrane also contribute to this. (d) The wing costal margin around and, especially, distal to the distal costal pivot (cpd) becomes reinforced with the costo-apical sclerotization, cas, or secondary pterostigma, while cpd is modified into a reinforced apical joint, aj. Overlapping fields B and C or only field C extended into the caudal portion of field B is an additional characteristic of numerous patterns of the “staphyliniform” type; this comprises a number of variants linked by transitions. The hydrophiloid folding pattern is here considered as the closest to the groundplan. It is observed in most of Hydrophiloidea s.str. (Fig. A36) and differs from the “clavicorn” pattern only by a movable CuA2 and a well-developed aj. A large but rather weak field B and a basad non-extended field C are among the other distinctions of this folding pattern. The couple of folds e2–hx turned basad is also characteristic. This adds to the similarity between the hydrophiloid and “dryopiform” patterns, being a precondition for the former to evolve into the latter. This transformation, however, occurs rarely because a strong cas usually prevents the fold e2 from meeting aj. In addition, the fold hx is often underdeveloped, being split into irregular folds. The scarabaeoid folding pattern (Sphaeritidae, Synteliidae, Scarabaeoidea, Figs A42–62) stems from the above evolutionary trend. Concisely, this can be formulated as the anterior part of the apical membrane being transformed into a stiffened lobe which deflects at the apical joint while remaining non-folded transversely; as a result, the wing folds like a jackknife. The wings of Sphaeridiinae (Figs A: 38, 39) and Saprininae (Fig. A40) can also be placed in this group while the histerine folding pattern (Histerinae, Fig. A41) is to be considered as a not too advanced derivation chiefly distinguishable by the wing apex folded transversely, as well as longitudinally, with the aid of multiple secondary folds parallel to the fold la. The staphylinoid folding pattern (Staphylinoidea) can briefly be defined by the presence of field Hs or fold hi+ as the posterior border of the field (Figs A: 63, 64, 66–68). The field Hs emerges from the anterobasal portion of field H adjacent to field S and delimited by folds la and hi. This is one of the few secondary folds of the hw-group which originally radiates from the base of MP3+4 (Fig. A66). It runs between RMP and MP3+4, directly extending into the fold xi; the latter tends to proceeding parallel to the fold la in the course of evolution. The staphylinid folding variant (Staphylinidae s.l., Silphidae, Figs A66–69) of the pattern involved is closer to the groundplan. Small and very narrow fields S and D, a long and narrow field C and a totally reduced B characterize it. Where field B had formerly been situated, a secondary field Bs was formed. It also incorporated the area Q, thus becoming contiguous to field D. The entire

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field association C–Bs–S–D contributes little to folding, hence it strongly tends to be reduced along with fold hw, resulting in field Hs and secondary fold xx functionally substituted for field D and fold hw (Scydmaenidae). The agyrtid folding variant (Figs A: 63, 64) differs by an originally lacking field Bs, an almost completely reduced field association C–S–D and a basad extended field Hs of a tetragonal or triangular shape, instead of a pentagonal one. As a consequence, fold hw is totally reduced, cpd almost so; therefore, the fan-folding is replaced by a flat one, including a transverse folding along the fold line e2–hx–xx, xx being a secondary fold in field X. Finally, the scydmaenid folding variant is intermediate and likely to be annectent between the above two variants. The field association C–S–D is totally reduced, fold hw as well. As a result, the proximal corner of a triangular field Hs enters the wing costal margin at the former cpd, the latter thus persisting as a weaker cpdII. The other characteristic features are almost the same as in the previous variant, being especially close to the folding pattern of Leiodidae (Fig. A64). The nitidulid folding pattern (Nitidulidae, Brachypteridae), as well as that of Sikhotealinia (Fig. A30) are also to be included in the present type. The former fits in well with the scarabaeoid folding pattern but for a lacking apical joint. The latter is also different in fields S and D being not that long, as well as in a quite closed field R, thus approximating to the “dryopiform” folding pattern in the latter character. The following three subtypes are the most profound modifications in the “clavicorn” folding pattern. All of them share a closed field R by which Forbes (1926) defined the subtype “Dryopiformia”. The “dryopiform” subtype (Figs 39 d–f; A: 80, 96, 98, 99, 108, 109, 150–152, 161, 198, 199, 206–209, 218–224, etc.) is peculiar to the wings with a longer apical membrane, ca 27–65% of the total wing length. It occurs since free apices of the folds e2 and hx meet the distal costal pivot (cpd) and the apex of fold hw, respectively. The portion of the field E lying proximal to the fold e2 thus becomes an independent, closed, triangular field R. The field H gets closed trapezoidal in the same way. In the course of further evolution, the fields R and H tend to growing increasingly internal and small (e.g. Fig. A221), with a convex fold of the secondary apical hinge getting longer. The fold hw either intersects CuA2 or it does not. This folding type is developed in parallel in numerous Coleoptera (Table 1). It often occurs also in Tenebrionoidea and Cleroidea, but never in Chrysomeloidea. It is linked up with the “clavicorn” subtype by transitions and is likely to have stemmed from it in two ways, as follows. The folds e2 and hx turning basad in couple is the first and apparently most frequent pathway. It is such a way that intermediate patterns of some Cleroidea (Figs A: 226, 230), Zopheridae (Fig. A154) and primitive Curculionoidea (Fig. A215) seem to have appeared; in these, at least one of the fields R and H is not quite closed.

“serricorn”

adephagan scirtoid “clavicorn”

“diversicorn” group

polyphagan

Type Subtype archostematan cupedid schizophoroid

“protomelyrid” byrrhoid salpingid “pseudobostrichoid”

nominate

Taxon Archostemata Archostemata: Schizophoroidea (Schizophoridae, Catiniidae) Adephaga, Myxophaga Scirtoidea Cerophytidae, Buprestidae (Anthaxia), Dermestidae, Endecatomidae, Mordellidae, Rhipiphoridae, Stenotrachelidae, Oedemeridae, Tetratomidae, Zopheridae, Boridae, Tenebrionidae, Mycteridae, Salpingidae, Sphindidae, Byturidae, Biphyllidae, Erotylidae, Laemophloeidae, Propalticidae, Phalacridae, Chrysomeloidea, Trogossitidae, Cleridae, Melyridae Melyridae Callirhipidae, Ptilodactylidae, Byrrhidae Salpingidae, Pterogeniidae, Silvanidae Tenebrionidae, Sphindidae (Sphindus) Eucnemidae, Throscidae, Elateridae, Lycidae, Omethidae, Lampyridae, Lymexyloidea, Rhipiphoridae, Oedemeridae, Melandryidae, Tetratomidae, Zopheridae, Prostomidae, Tenebrionidae, Synchroidae, Trictenotomidae, Pythidae, Pyrochroidae, Anthicidae, Meloidae, Scraptiidae, Aderidae, Anaspididae, Erotylidae, Passandridae, Cucujidae, Silvanidae, Bothrideridae, Helotidae

Table 1. Distribution of folding patterns in the Coleoptera Variant

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Group

94

Type polyphagan

“dryopiform”

Subtype staphyliniform

monotomid “postdryopiform”

curculionid

“eudryopiform”

nitidulid “hemidryopiform”

histerid staphylinoid

Group hydrophiloid scarabaeoid

coccinellid

cryptophagid

nominate diaperine curculionoid

staphylinid scydmaenid agyrtid

Variant Hydrophilidae Hydrophilidae, Sphaeritidae, Synteliidae, Histeridae, Scarabaeoidea Histeridae Staphylinidae s.l., Silphidae Scydmaenidae Ptiliidae, Hydraenidae, Agyrtidae, Leiodidae Nitidulidae, Brachypteridae Zopheridae, Trogossitidae, Cleridae Tenebrionidae Belidae, Nemonychidae, Anthribidae Georissidae, Elateridae, Ptilodactylidae (Forbes, 1926), Chelonariidae, Dryopidae, Heteroceridae, Limnichidae, Elmidae, Derodontidae, Mycetophagidae, Archeocrypticidae, Ciidae, Tenebrionidae, Zopheridae, Salpingidae, Erotylidae, Endomychidae, Coccinellidae, Corylophidae, Discolomatidae, Lathridiidae, Cerylonidae, Bothrideridae (Bothrideres), Melyridae (Forbes, 1926) Cryptophagidae, Phloeostichidae, Curculionidae, Anthribidae, Urodontidae, Attelabidae, Brachyceridae, Barididae Derodontidae, Endomychidae (Forbes, 1926), Coccinellidae Monotomidae Jacobsoniidae, Tenebrionidae, Brentidae

Taxon

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Type polyphagan

elateroid

bostrichoid

Subtype melyrid

cantharid buprestoid

Group melyrine malachiine “probostrichoid” megatomine bostrichid anobiid nosodendrid elaterid

schizopodine buprestid dascilloid

Variant

Melyridae Melyridae Endecatomidae, Bostrichidae Dermestidae Bostrichidae Anobiidae Nosodendridae Artematopodidae, Brachypsectridae, Eucnemidae, Throscidae, Elateridae, Omalisidae, Eulichadidae, Melandryidae (Serropalpus) Cantharidae Buprestidae Buprestidae Dascilloidea

Taxon

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The salpingid (Figs A: 174, 175) and probably also byrrhoid (Fig. A95) folding patterns seem to be among otherwise formed transitions. Following this pathway, field R becomes closed first, and field H after, since either a secondary fold analogous to hx or a joint fold hx–hxa is formed. In this case, the internal but simple cpd seems to be a precondition for the closed field R to appear. When such a cpd occurs, folding deformations are to form around the field D’s corner. Ordering these appears to be a good explanation as to why either fold e2 changes its orientation or its analogue is formed. The series Salpingus or Istrisia (“clavicorn” folding pattern) – Prostominia – Sphaeriestes (“eudryopiform” folding pattern) illustrates well how field H becomes enclosed with the joint fold (Fig. 40). Prostominia is keystone in this series because a three-branched fold hx is present there. Among the hx branches, the internal one, hxa–, encloses field H, thus drawing the folding pattern superficially close to the “eudryopiform” one, except for the field H being pentagonal, not tetragonal, in shape. As the “dryopiform” folding pattern evolves, two main tendencies are seen towards field transformation in the apical membrane. Of them, the first terminates in strongly to completely reduced fields D and S ( Jacobsoniidae, Brentidae, Monotomidae) while the second leads the tip of a convex fold x3 (or fold x3–x3a, by analogy with hx–hxa) to be turned basad until entering the posterior corner of the field H. As a result, the anterobasal portion of field X becomes an independent, closed field Xh triangular (Figs A: 108, 109, 208) or tetragonal (Figs A: 198, 199, 215–224) in shape.

a

c

b

d

Figure 40. Two probable pathways (a–b–d or a–c–d) in the evolution of the “clavicorn” folding pattern into the “dryopiform” one; a–d, evolutionary stages: Istrisia (a), Prostominia (b), Rabocerus (c), Sphaeriestes (d).

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Based on the above evidence, the “dryopiform” folding type comprises a number of folding patterns of different grades which can be arranged in the following way: (1) The “hemidryopiform” folding pattern includes patterns with at least a not quite closed field R. Of the patterns belonging here, two require special mention. The diaperine variant is distinguishable by the combination of a quite separate internal cpd and the fold e2 which starts serving as the apical hinge (Fig. A164). The curculionoid variant is defined by the field Xh (Figs A: 215–217, 220). (2) The “eudryopiform” folding pattern fits in well with the groundplan of the “dryopiform” subtype. The field Xh is absent; fields S and D are well-developed or somewhat reduced in size; cpd is either external (cpdd, Fig. 39d) or internal (cpdi), combined with the secondary apical hinge (Figs A: 96, 98, 99, 107, 150–152, 161, 206, 207, 209). (3) The curculionid folding pattern is derived, since field Xh is present while fields D and S are reduced in size. Its cryptophagid and coccinellid (sub)variants contrast in a particular shape of the field Xh, as well as in the relative position of CuA2 and fold hw. The former (Cryptophagidae, Phloeostichidae, most of Curculionoidea) demonstrates a tetragonal field Xh, with hw intersecting CuA2 at the base (except as shown in Fig. A218). The latter variant differs by the combination of a triangular field Xh and the fold hw lying distal to CuA2 or its basal half (Laricobiinae and Derodontinae, Derodontidae; some Coccinellidae and Endomychidae); in addition, the field H can be secondarily triangular in this pattern (Fig. A208). (4) The “postdryopiform” folding pattern (Figs A: 109, 166, 224) contains derivatives of both curculionid and diaperine patterns. The fields C and H are fused into a longitudinal field because of totally reduced fields S and D in between. In Brentidae, the proximal part of the field R becomes an independent field. It also seems possible to derive the monotomid folding pattern (Monotomidae, Fig. A200) from the “eudryopiform” one. That pattern closely resembles the nitidulid one because both share congruent fields D and S, as well as a straight fold line sd–la and the vein CuA2, the latter intersected at the base by fold hw. Yet the following two characters suggest different origins of the patterns involved: (1) fairly long fields D and S, and (2) two transverse sclerites, instead of only one, abs, inside the field D. Besides this, a rudimentary fold separates these sclerites during the earlier folding of the wing, the fold occurring in couple with its counterpart inside the field S while being absent from the folded wing. The sclerites may be abs and aas, as well as the folds may be de and sh. Were it true, the above fields D and S would be nothing but D+R and S+H, respectively. The melyrid subtype. This is rare as occurring only in advanced Melyridae. It combines separate features of the salpingid and “dryopiform” folding patterns,

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but differs from the latter in a lacking counterpart of the fold de. The apical hinge conforms to the distal section of the fold de/e2+. This subtype originates from the “clavicorn” groundplan (Fig. A232) through an intermediate stage corresponding to the “protomelyrid” folding pattern (Figs A: 233, 234) of the latter subtype. The pattern reaches completion since the field R is almost closed by the tip of fold e2 at cpd while the other free folds of the apical membrane are reduced to only three, e3, la and hw. These three folds are stable in position in the wing, with the latter two ones running more or less parallel to each other (Figs A: 234, 235). As this pattern evolves into a more specialized one, the field C increasingly shortens through its proximal corner shifted distad (Fig. A235) while the posterior corner of the field appears frontal to MP3+4. The melyrid pattern proper is defined by the combination of a strongly internal cpd, the fields D and R strongly reduced in size and a lengthwise D. Each of the following two folding variants could have originated either from the melyrid or “protomelyrid” folding pattern. The melyrine variant has anyway resulted from simplification of the groundplan pattern by merging the fields C, S, D and H into one field (Fig. A235; Astylis: Forbes, 1926, fig. 124). In contrast, the malachiine variant has come out of field differentiation. Namely, two closed fields, H1 and H2, were separated from field H’s anterobasal portion while the remainder of H occupied peripheral parts of the areas W and V, resulting from the CuA2 base intersected by the fold hw (Fig. A236; Collops: Forbes, 1926, fig. 125). The bostrichoid subtype. This is a special derivation of the “clavicorn” folding pattern, the closest to that of Endecatomus or some Dermestidae, e.g. Orphilus. It began to form since a strongly internal cpd had appeared (Figs A: 121, 122), this being the characteristic feature of the most advanced variants of the “dryopiform” folding type. The bostrichoid folding pattern differs from the “dryopiform” one primarily by the following two characters: (1) the secondary apical hinge is concave, so it can be identified as the distal section of the fold dq; and (2) the folds e2 and hx are never cooperating. This subtype is certain to have resulted from a transition to wing folding using secondarily reinforced bending zones in the cubital and, especially, costal bars. An enlarged field B and the cb apex detached from the wing costal margin were basic modifications for these zones to operate. It is the latter modification that appears to have given rise to many secondary folds, some of which convex, the other concave; all these radiated from cpdi to the anterior wing margin (Orphilus) which were then oligomerized to only a single apical hinge. Forbes (1926) failed to adequately interpret this type. He confused the field R and the basal part of the field E with fields S and D, respectively, apparently considering the true fields S and D as secondary. Following this

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misinterpretation, the folding patterns of some Bostrichoidea were placed in the scirtoid folding subtype. Particular folding patterns: The “probostrichoid” folding pattern (Lyctus, Lyctinae, Fig. A122; some individuals of Megatoma or Endecatomus) is a slight modification in the “clavicorn” pattern, supposedly the closest to its groundplan, but cpd is strongly internal (cpdi). The megatomine folding pattern (Dermestidae: Megatominae: Anthrenus, Fig. A113, some individuals of Megatoma): the only field composed of fused fields D, R and the proximal part of E occurs between the folds dq and e3 because the folds de and e2 are reduced; the field S varies from not to strongly extended caudad. The bostrichid folding pattern (most of Bostrichidae, Figs A123–125): two complex fields are present, C+S+H and D+R, the former open, the latter closed and tending to be reduced. The anobiid folding pattern (Anobiidae, Figs A115–119). A large, triangular, complex field, either C+S+D or, when C is reduced, S+D, is interposed between the field H and the area W. A tendency towards the folds sd, de and la in decline culminates in the fields D and R first transformed into a wrinkled region and then merged into fields lying caudal to them. In Ernobiinae and Ptininae, a new field, B', replaced B in the course of C reduction, having resulted from a new fold, b'q, formed distal to the bq proper, with fold bw extending into cq. The posterior (superficially distal) corner of field B thus “migrated” distal to “r–m”. The nosodendrid folding pattern (Nosodendridae, Fig. A114). Two large, internal, contiguous, triangular fields distal to the field B are the main distinctions. These are very likely to be C+(S)+D and R while resembling the fields C and S, respectively. The latter field seems to have been reduced while R extended backwards due to the extrusion of the fold sh by the fold de growing progressively long. The elateroid subtype. Its groundplan (Fig. 6) is characterized by a unique ensemble of the central field group which is chiefly due to two intercalary fields, one anterior (Ia), the other posterior (Ip), both inserted between the fields C, S and D. The fields F and G are reduced either partly or, more seldom, one or both totally. The field B is replaced by a secondary field situated proximal to it, except in the groundplan (Fig. A70). This substitution was accompanied by a basad extension, often a strong one, of the field C. A rolled wing apex (Fig. A70) may be a protofeature. The field D is primitively open (Figs A: 70, 71, 73–75, 77, 78, 84, 86, 100–103), versus closed in all other cases. The folding pattern as above has only persisted in primitive Elateroidea and in Eulichadidae, Byrrhoidea, occasionally occurring also in Serropalpus (Fig. A143), Melandryidae. In many other Elateriformia, the field Ip has disappeared either together with S (Figs A: 92, 100–103, 106) or, most frequently, with Ia

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(Anthaxia, Buprestidae; Byrrhoidea; numerous Elateroidea, Figs A: 71, 73, 76, 80–82, 88–90). The former folding pattern is highly peculiar, whereas the latter fails to differ from the “serricorn–clavicorn” type. Assuming the fields of the I-group is a derived character1 probably resulted from an almost lengthwise field D, one could readily derive the elateroid folding type from the “clavicorn” type. The question arises from this evidence as to how the elaterid and byrrhoid folding patterns interrelate morphogenetically. I rather adhere to deriving the latter from the former, thus holding the elaterid folding pattern as the groundplan of Elateriformia but Scirtoidea. Particular folding patterns are as follows: The elaterid folding pattern (Figs A: 70, 72, 74, 75, 77–79, 83–87, 93) ranges between almost groundplan (Artematopodidae) and the patterns defined by a very long field C, as well as a partly to completely reduced field B. The buprestoid-cantharid folding group. The field Ia is well-developed, both Ip and S are totally reduced, D is either closed (Cantharidae, Buprestidae) or widely open (Schizopodinae, Dascilloidea). Although very similar in the folding pattern, Cantharidae and Buprestidae + Dascilloidea have acquired it from different groundplans, i.e. in parallel, this certainly following from the profound differences between both groups in wing venation, sclerotization, as well as the structure of the articular region. Superficially, the cantharid folding pattern (Cantharidae, Fig. A92) is of the “serricorn” type due to a basad strongly extended field C; the field Ia is very large and congruent to the field D or nearly so. The buprestoid folding pattern (most Buprestidae, including Schizopodinae; Dascilloidea) embodies three variants. Among them, the buprestid one (Fig. A106) differs from the schizopodine variant (Fig. A103) only in a closed field D. A tendency towards a strong reduction both of almost all folds and the transverse folding, the latter by means of a reduced costal bending zone, is also characteristic (Figs A: 104, 105). The dascilloid variant is defined by a different orientation of the field Ia which posterior corner lies much proximal to the anterior and distal corners, these being subequally distant from the wing base (Figs A100–102). Among the latter three patterns, the schizopodine one is here recognized as close to the groundplan and thence ancestral to the buprestid and dascilloid patterns. The schizopodine and buprestid patterns are certainly closer to each other than to the dascilloid one. This disagrees with Forbes (1942) who believed that Schizopodinae and Dascillidae were closer to each other in this character. 1

The grounds, albeit rather weak ones, for such a treatment is that the fold la, including cq and sd, is concave in all folding patterns, except for the elatrid one in which the convex fold di is interposed between the folds cq and sd.

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The folding apparatus The folding apparatus folds the hind wing both longitudinally and transversely. The longitudinal folding resulting in the jugal lobe tucked along the jugal fold is not discussed further. Unlike this primary folding which has only retained a little modified by the Coleoptera, the transverse folding of the wing, with the respective functional apparatus in use, is a novelty and characteristic feature of the beetles. A priori one could suggest two possible ways to reduce the beetle hind wing in length during folding, based on studies as to how the other insects fold their wings. The first way, a transverse and flat folding of the wing apex is the simplest and, consequently, the most easily achievable. However, it would give rise to a stronly interrupted axial support of the wing, especially its leading edge. Beetles evolved a different way which was based on and likely started from a weak and smooth costal bending zone in the wing plane. On the one hand, this way was not so efficient as the above could be because the wing length was only slightly reduced by folding. In addition, it raised much more numerous deformations in the central regions of the wing, these being chiefly the folds radiating from where the costal bending occurred. But then these deformations troubled the leading edge support the least while repeated bendings of this support to and fro seem to have preconditioned an early beetle wing for the development of a folding mechanism peculiar to the extant beetles. It also follows that the folding pattern was complex already at the earlier stages of beetle wing evolution. As integrants of this pattern, closed fields should have been formed in the central wing regions, with peripheral folds being accessory. Of the groundplan fold set, many folds were novelties, but some probably derived from flexion-lines. More specifically, the transverse flexion-line might have given rise to the fold hw. Likewise, the distal and basal sections of the medial furrow, the antecubital furrow and different sections of the claval furrow seem to have been predecessors for the folds la, ap, au, fu and gv, respectively. Although we know little about the earlier evolution of the beetle folding apparatus, this appears to have passed through two phases, basal transverse folding first and apical transverse folding after. A general evolutionary trend can be revealed in the following successive evolutionary stages: a weak basal folding through cbz – a strengthened basal folding by means of cpp/cbz or cpp/cj – a weak apical folding and a strong basal folding combined (ah + cpp/cj) – substitution of a strengthened apical folding (cpd) for the basal folding. Although I am not certain if the beetle protowing is a beetle wing at all, I tentatively believe it possible to refer the protowing folding pattern to an early, hypothetical stage in the evolution of beetle folding. In this folding pattern, the

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fold line bq–hw played the leading role: the wing apex distal to this line was folded fanwise while the field B was apparently still less functional, being represented by a triangular area enclosed with folds of adjacent fields. Entering the next stage (Figs 41a, 45, 50a) resulted from wing folding having become more efficient due to a stronger costal bend in use. This led the folds of the apical fan to become reduced to only one strong fold, la, and made the field B not only functional, but also major in the folding pattern. The latter event could hardly have happened had it not been preceded by partial reduction of the field B in size, combined with some change in B orientation, the anterior field corner shifting distad being among the most probable changes. At this stage, the archostematan folding type could have been formed: closed fields in the wing basal part reached their structural completion while the fields H and C started differentiating from the apical folding sector. The fold line bq–hw functionally remained still significant. Axial supporting structures under the influence of large fields B and A were modified. Longitudinal veinal trunks along the costal margin united in a solid bar, at first radial and then costal one, probably resulting from the impact of the proximal costal pivot, cpp. CuA became almost abruptly interrupted at the cubital pivot where the fields A and G met. How the wing apex folded originally and the radial bar did bend at cpp remains uncertain. An apical roll (Forbes, 1926; Ponomarenko, 1969, 1972) and smooth bending zones in the costal and cubital bars (Kukalová-Peck & Lawrence, 1993; Beutel & Haas, 2000) are usually recognized as coleopteran plesiomorphies. It seems appropriate to regard the adephagan, cupedid and schizophoroid folding patterns only as modifications in the above folding type, albeit these being more or less profound. Based on the shape of the field B, the shape and topography of less movable areas Q and W, coupled with the presence of cbz instead of the costal joint, the folding apparatus of Adephaga + Myxophaga is to be considered more primitive than that of Cupedidae. What could have started the next evolutionary stage was the origin of the polyphagan folding type (Fig. 41b). This might have emerged from flattening the apical roll which became spiraled in reverse to the condition observed in extant Archostemata or Adephaga. This could have resulted in fields C, S and D’s differentiation in the basal portion of the formerly entire apical folding sector. Since then these fields, especially D, became responsible for transversely folding the wing, whereas the fields B and A showed a pronounced tendency towards reduction through increasingly loosing this function. Based on this, the region of the greatest folding deformations was extruded beyond the wing basal part, with two sequels occurring for the wing. A less reducible wing apex and thence a generally less efficient folding became the first, negative effect. The second, posi-

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a

b c

g d

e h

f

Figure 41. General trend in the evolution of the folding pattern in Coleoptera; a–h, folding patterns conformable to the evolutionary stages in succession: cupedid (a), polyphagan (b), “clavicorn” (c), “eudryopiform” (d), curculionid (e), “postdryopiform” (f); “serricorn” (g); coccinellid (h).

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tive one was a much weaker impact of wing folding upon the wing basal part as the body of wing support, for which reason the main supporting axes, the costal and cubital bars, became not as strongly deformable at the respective pivots as before. These characters having been acquired, contributions of the supporting axes to wing folding/unfolding were mainly restricted to to and fro changes in their relative position. This attempt to eliminate the undesirable folding deformations of the leading edge support seems to have been more successful than an earlier one seen in Schizophoroidea. This latter was executed by changing field B orientation, with strongly narrowing the anterior angle of the field which adjoins the radial bar. As the polyphagan folding type developed, the field B stepwise left its function for the field D. A widely open field D (Fig. 41b) became only the precondition for a still large field B in decline because it could serve only for lengthwise folding the wing apex distal to the field B, thus giving the folded wing the minimum reduction in length. This folding pattern fitted in with the scirtoid folding subtype and became intermediate between the archostematan and polyphagan folding types: it was already advanced morphologically but archaic functionally. The former peculiarity was due to the well-developed fields S and G, the latter to a strong cpp in operation. A complete or almost complete functional replacement of the field B by D took place as the “diversicorn” folding pattern developed, this being the groundplan for most polyphagan groups. At the earlier evolutionary stages, a strongly reduced field B was combined with a still open field D (Mordellidae, Stenotrachelidae, Rhipiphoridae, some Elateroidea, Byturidae). Since closed, the latter field and, consequently, the external cpd (Fig. 39c) became full functional homologues to the field B and cpp, respectively. The “clavicorn” folding pattern (Figs 41c and 46), being the groundplan of the “diversicorn” type, evolves into the “serricorn” pattern (Figs 41g, 47, 50e) as a tendency develops towards totally reduced proximal costal and cubital pivots. This results in strongly to completely reduced fields B and A, as well as a basad strongly elongated field C. The “clavicorn” and “serricorn” patterns remain capable of transforming into each other until the rather feeble quantitative differences they show turn into qualitative ones. Besides this, the “diversicorn” folding type is surely heterogeneous: while underlying most of the polyphagan folding patterns, probably including those of the elateroid type, it comprises derivations of the latter pattern as well. The “serricorn” subtype is predominantly peculiar either to larger beetles or those with longer elytra. It is inferior to the “clavicorn” pattern in efficiency because a reducible wing length never exceeds 40% of the total. On the other

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hand, based on the comparative simplicity of the “serricorn” pattern, one could anticipate a considerable increase in folding efficiency resulting, e.g., from accelerating the folding/unfolding processes or making the wing support less deformable. The latter character having developed, the reinforced costal and cubital bars appear to also contribute to flight qualities. It is noteworthy, too, that the anterior fold cq of the field C which substitutes for the fold line ap–bw–cq in the “serricorn” pattern grows to serve as a strong supination line (the remigial furrow) (Brackenbury, 1994). The “serricorn” folding pattern reaches its completion with the field C extended to the wing base while the field B reduced (Figs 41g, 47, 50e). Since then, the transition from accumulated quantitative structural changes to qualitative ones ceases, hence the wing system thus upgraded prevents itself from reversals. The occurrence of a typically “serricorn” folding pattern in rather small-sized Tenebrionoidea (Anthicidae, Aderidae, etc.) provides good support to this assumption. The other folding types have likewise stemmed from the “clavicorn” pattern, i.e. in the course of rather faint qualitative or quantitative changes rapidly turning into significant qualitative ones. A movable CuA2, the cpd transformed into aj and the costal wing margin reinforced distal to aj seem to have been preadaptations for the staphyliniform folding mechanism to evolve into a “simplified”, fanwise one. A higher efficiency of folding resulting from a deflected wing apex largely elongated due to the movable CuA2 proved useful to the beetle groups which were distinctive in having a stout hindbody, enabling the elytra to further shorten. The subsequent evolution of the staphyliniform folding type seems to have proceeded in two directions, as follows. In the rather weakly costalized wings of typically scarabaeoid folding patterns (e.g. Scarabaeoidea), the central folding through fields B, C, S and D persisted as modified, however a little. In particular, the field C became somewhat shorter, with its proximal corner strongly shifted forwards and the posterior corner sometimes drifted backwards. This led to a redistribution of the field C’s functions: its participation becomes the least in the longitudinal folding, but more substantial in the transverse one. The field B somewhat reduced from this alteration, but, together with the field C, it induced the proximal costal pivot to intensify its function and thus resulted in a reinforced costal bending zone, cbzII. Conversely, a strongly shortened basal part of the wing in Staphylinidae and Silphidae invited the central folding to decline and, consequently, a stronger costalized basal part. As a result, the fields D and S, coupled with Bs and C, got increasingly reduced in size, especially in width, while the apical

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folding became more complex than before due to a longer apical membrane. In terms of evolution, this trend went towards substituting the apical hinge for cpd, with cpp having being reduced long before. The tendency further proceeded through an intermediate stage of the scydmaenid folding pattern and culminated in the agyrtid one, with not only cpd replaced by ah, but the latter also supplanted by a secondary (more exactly, tertiary) apical hinge in the form of a e2–hx–xx fold line. The following three folding subtypes arose from enclosing the field R alone or coupled with the field H. For the “dryopiform” and bostrichoid patterns, this transformation stemmed from a deep evolutionary tendency towards an increasingly elongating apical membrane. As the tendency was embodied, at least the fold e2 turned basad stepwise until the distal costal pivot became doubled. Since completed, this character inhibited the above folding patterns from reversion to the “clavicorn” one they had originated from, thus determining these patterns to further developments within themselves. The following succession of patterns, “eudryopiform” – curculionid – “postdryopiform”, defines the main trend in the evolution of the “dryopiform” subtype (Figs 41d–f). In this series, the groundplan folding pattern at first became more complex by adding a closed field Xh to the others. At the final stage of evolution, this folding pattern overloaded with closed fields (consequently, with too many links in the kinematic chain of folding) was simplified to the “postdryopiform” one. The latter emerged from obliterating the older fields, these having been strongly reduced in size and thus contributing less to the folding process. Different variants of the curculionid foldind pattern, especially the “eudryopiform” one, frequently occur in the Coleoptera (Table 1), parallel developments of these patterns being regular evolutionary events. That the “eudryopiform” and “hemidryopiform” (diaperine) folding patterns (Fig. 42) have evolved into the “postdryopiform” folding pattern independently seems to be the best illustration. The latter pattern is observed very rarely, probably because of its evolutionary youth. The bostrichoid folding subtype embodies the greatest variety of far advanced folding patterns. These occur nowhere else but in Bostrichoidea. This is very likely due to the particular groundplan character set and consequent way of folding. This could have restricted the adaptive zone of the wing, thus making its evolution more or less orthogenetic. The internal cpd, coupled with a concave apical hinge and an open field H, seems to have constituted this unique character combination. As an extrinsic structure, the abdomen strongly involved in the wing folding apparatus might have contributed much to the development of numerous if not all of the folding patterns of the “bostrichoid” type.

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Patterns of the melyrid folding subtype are of highly limited distribution. They share some morphological features with the “dryopiform” and salpingid folding patterns, emerging from the “clavicorn” pattern so as to probably serve for an accelerated wing unfolding or folding with a more strongly reducible wing apex due to truncated elytra. The elaterid folding pattern is sure to have given rise to the elateroid folding subtype. This conclusion can be drawn from the pattern that underlies the folding groundplans of Elateroidea, Byrrhoidea and Buprestoidea plus Dascilloidea, i.e. those of all of the elateriform superfamilies but Scirtoidea. The “serricorn” and “clavicorn” patterns of elateriform beetles are nothing else but derivatives of the elaterid pattern, albeit these seem to have developed in parallel in numerous Elateroidea, some elaterids included, and the Byrrhoidea but the Eulichadidae. To summarize, one comes to the conclusion that the general trend in the evolution of beetle folding patterns is well traced in the following succession: archostematan – polyphagan – “clavicorn” – “dryopiform” – “postdryopiform” (Fig. 41). This trend was defined by a staged centrifugal differentiation of individual folds or fold couples distal to the field B, associating these folds into open fields of unstable shape. Then these became closed, chiefly triangular, and associated with one another in new structural-functional units which were step-by-step added to the groundplan field pattern B–A–G. The C–S–D unit was added first, the R–H unit after, while the field Xh still afterwards. As this occurred, some former fields or field units lost their functions, thus reduced in part or entirely from merged into newly formed fields to obliterated. Each of the above folding patterns corresponded to a particular evolutionary stage and was defined by special combinations of principal pivots and hinges at the wing costal margin. This succession was as follows: cpp – cpp+ah – cpd – cpdd (cpde or cpdi+ahII) – ahII (Fig. 39). Figure 41 shows that the folding pattern became more complex in the series c–d–h (c–f ), this taking place as the apical membrane grew longer in the course of total wing length increase (relative to body length). Beetles developed two ways to fold a longer wing apex. Of them, the first and also the most frequent was the evolution of the “clavicorn” folding pattern first into the “dryopiform” one and then into its derivatives (Fig. 41d–f). The second could have led to manifold variants of the staphyliniform folding subtype, including such highly specialized derivations as the agyrtid folding pattern; this latter is hardly different functionally from those of the “dryopiform” subtype (Fig. 41f). Apparently, the differences between the two solutions to the problem were essential, at least at earlier evolutionary stages. In the former case, wing transformations predominantly involved the folding pattern. In the latter case, the basic adaptation, on the contrary, only slightly modified the groundplan folding

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pattern, but anyway required transformed supporting axes, the movable cubital spur in particular (Fig. 50g, h), usually also a more flexible costal bar. The above transformations, as well as a growing wing length which they had stemmed from, largely arose from size evolution towards miniaturization. Shortening the elytra and compacting the body sometimes emphasized its impact. Deviations from this general evolutionary trend towards folding patterns of higher complexity occurred rather occasionally. These were infrequent simplifications of the “serricorn” (Lymexylidae, Rhipiphoridae) or buprestid (numerous Buprestidae) folding pattern. The simplifications resulted from a totally reduced transverse folding component, coupled with the longitudinal folding component being either reduced or modified fanwise; all these alterations left a lengthwise wing folding along the jugal fold almost unmodified. Although different groundplans underlie the reduced folding patterns, these approach one another in appearance as all of the folds become increasingly lengthwise while closed fields (C, A and B) get progressively narrow until reduced. Figures 42 and 43 show probable morphogenetic interrelationships between the main folding types or patterns.

Figure 42. Evolution of the “dryopiform” folding type. Arrows correspond to the directions of morphogenesis.

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Figure 43. Evolution of the groundplan folding pattern in Coleoptera. Arrows correspond to the directions of morphogenesis.

The supporting system The hind wing support in beetles is of three kinds. True veins, membrane sclerotizations and secondary “veins” of membrane origin are these kinds. The veins are most important to provide the wing with the necessary ratio of rigidity to flexibility (deformability). Membrane sclerotizations, secondary “veins” included, are added to the veins in the course of later beetle evolution. These novelties either substituted for the veins where these had been lost or deficient originally, or started performing special functions to localize deformation lines in the wing

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membrane, especially folds, by preventing these from crumpling during folding. Certain flexion-lines and fields contribute a little to the wing support as well. Veins. The supporting function of a vein is defined by a combination of such properties as rigidity and deformability. Their original balance changes since a fold or furrow intersects the vein. Wootton (1981, 1992) has shown that vein adaptations to flight deformations are similar in different insect taxa, among them short veinal sections desclerotized, i.e. provided with a soft cuticle, where intersected by furrows. As a result, the entire vein is lengthwise differentiated, with some of its sections contributing more to rigidity while the others more to the deformability of the whole. During folding the constituent parts of the wing change their relative positions much more strongly than in flight; therefore, folds trouble the veins to a greater extent than furrows do. Structures of two kinds are responsible for the stronger deformability of an individual vein in beetle wings. There are predominantly abrupt and annulated veinal breaks same as above. These prevent bending veins from damage, yet not from performing defensive functions with regard to nerves and tracheae, as well as to haemolymph transport. The veinal breaks, because of these peculiarities, are chiefly present in veins of the central wing regions and in veinal trunks. A vein transformed into a weak flattened strip is the second kind of modification involved. Such strips are only confined to the wing periphery due to a strong decline of all functions but the supporting one. Longitudinal strips of the apical membrane of archostematan and adephagan wings are illustrative examples of these structures. When equipped with two or more breaks in neighbourhood, a vein ceases to serve as support and tends to be totally reduced. The RP+MA section between RP and r1 is a telling illustration of how this could have happened: being twice intersected by the field B, that vein tended to be obliterated in all Recent Coleoptera but Archostemata. Adaptations of complex supporting structures to folding can be different from the above, also being complex. The costal bar of Adephaga is illustrative in this respect. Namely, the corrugation of cb throughout its length contributes much to a higher deformability of the bar. A lengthwise differentiation leaves the bar subdivided into two sections, a broader basal and a much narrower distal section, thus adding to the rigidity of the former and to the flexibility of the latter. A crosswise differentiation of cb results in its distal section subdivided into two parts, contributing to a redistribution of the rigidity and flexibility within the costal bar as well: the frontal part largely serves as support while the caudal one (represented by a desclerotized RA) is responsible for a higher deformability of the entire section. Venation. Wing venation was reduced in the course of the historical development of Coleoptera. Many of the basic elements disappeared, albeit not

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merely from successive reductions of certain veins alone. Firstly, the evolution was more complex: reductions of certain veins were combined with the conformation of complex and jointed veins, as well as veinal units. Secondly, it was staged, each stage starting with the development of a particular venational groundplan, or venation type. It seems appropriate to begin with what underlies the wing venation of Recent Coleoptera. The main distinctions of this primitive, caraboid, venation type are as follows: (1) the wing apex, because of strongly reduced veins, is transformed into the apical membrane sharply contrasting with the basal, supporting part of the remigium; (2) there are only three, albeit stiffened, longitudinal veinal trunks in the remigium, among them the radial, medial and cubital bars braced by a few, also strengthened, cross-veins; these enclose the carpal and oblong cells; (3) a richly branched venation of the clavus. Secondary supporting structures are uncharacteristic as being either absent or (membrane sclerotizations) poorly developed. More or less profound corrections being made, this type can be applied to the wings of Adephaga + Myxophaga, Archostemata and Scirtoidea (Figs 17, 18, 20). Figures 15 to 18 illustrate how the above structural peculiarities have developed or at least could have been formed. More specifically, veins RP3+4+MA and MP1+2 having been merged medially into the shared base preceded a sharp subdivision of the remigium into the basal part and apical membrane. Cross-vein m4 was thus reduced between these veins, resulting in a simplified and, consequently, strengthened transverse brace lying between the leading edge support and the medial bar, MP–MP3+4. The brace took the appearance of a transverse jointed vein “r–m” which demarcated the wing basal part from the apical membrane. Because its apical branches were lost or modified into sclerotized strips, the vein RMP was transformed into a truncated rms. This terminated that morphogenetic stage, thus leaving the apical membrane with only two veins in support, these being RP1+2 and MP3+4, each modified into a weak strip. Longitudinal veins were reduced in number at the wing base, as well as in the middle of the remigium. At the wing base, M merged into R near the arculus (m–cua), following R superimposed on M, whereas the CuP primary base was obliterated along with the 1A base. Medially, ScP and R–RA became jointed lengthwise and thus associated in the radial bar. Only MP3+4 among the two apical branches of M persisted as being involved in the medial bar, M–MP–MP3+4. The cubital bar (CuA) got incrassate throughout and additionally reinforced basally through fusion either with the CuP primary base (Archostemata, Polyphaga) or with only a short section of CuP (Adephaga). In the former two taxa, Scirtoidea excluded, the cubital bar involved also the base of the medial bar (M–MP). Numerous cross-veins of the groundplan set were reduced to few, these chiefly confined to the apical region of the remigium basal part. Among them,

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the anterior- (r1, r2) and posteriormost (m–cu3, m–cu4) veins were incorporated in rigid supporting units of the radial and oblong cells, respectively. Together with “r–m”, these constituted a durable, but, when necessary, very flexible distal transverse brace between the remigium’s ultimate supporting axes, i.e. the radial and cubital bars. At the same time, the basal brace between the cubital bar and R which served as the body of the leading edge support grew shorter and simpler, since it had first been reduced to the simple arculus (m–cua, Adephaga) and then to the complex one (M+m–cua, Archostemata and Polyphaga but Scirtoidea). The evolutionary fate of M involved in this brace is evident from the above. Of the medial transverse braces, only one persisted, yet strongly modified into RP–MA–m1, the posterior part of which constituted the proximal border of the carpal cell. The other cross-veins of the groundplan set (m2, m–cu2) and primary complex transverse braces (m3 – MP1+2 base) were reduced in part or entirely. Many of the above venational elements developed breaks or bending zones to be easily deformable during folding, these in the radial or cubital bars being the most important. Longer and annulated desclerotizations occurred in some veins involved in the carpal cell, among them the RP+MA base, the apical section of the medial bar and “r–m”. In the clavus, the main if not only venational modification was reduction of the 1A basal section. This brought the anal loop to reduction anyway, no matter whether through opening or extruding the cell basad. Choosing between two results below, the first was that the clavus got narrower basally and came into a closer contact with the remigium through the first anal vein (AA3 or perhaps AA1+2+AA3) approaching the Cu–CuA base and even R (Figs 25–27). Secondly, 1a and a newly formed cell 2a together substituted for the anal loop as the body of the clavus’ support. Virtually all of the above modifications seem to have been basic adaptations to maintain the flight capability of beetles in the infancies of functional wing posteromotorism and hind wing folding apparatus. There is but very little doubt that these adaptations were necessary for the wing to resist a complex of new and implicitly dangerous deformations. These stemmed from a strong increase in wing loading, which was produced by a growing fall in the flight function of the elytra, probably accompanied by body mass increment, and also the development of a folding pattern. A possible adaptive significance of some of the principal modifications is discussed below. In particular, numerous veins reduced in the apical membrane while a strongly weakened remainder surely aided apical folding. In addition, this resulted in a lightened wing apex, with the centre of mass shifted basad, which decreased the inertial forces affecting the wing in flight. A lengthwise fusion of veins at the wing costal margin into a doubled (radial) bar first and a triple

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(costal) bar after seems to have been the only feasible way to adapt the leading edge support to folding by adding to its flexibility without detracting a great deal from rigidity. Crimping the costal bar was the following adaptation in this direction. The remigium’s basal part relieved from useless or less functional supporting elements proved favourable both for the folding and flight apparatus: this added to the movability of the costal and cubital bars relative to each other and also lightened the wing. The following two jointed veins formed, “r–m” and MA–m1, as well as the oblong cell which rigidly braced the apices of the medial and cubital bars, consolidated the remigium’s support and adapted it to folding. The carpal cell became support to a large field B while the basal section of the medial bar to the anterior fold of a large field A. There are two accounts for the basalmost part of the wing to become the best consolidated among the other wing regions. Firstly, it is this region where the major deformation lines converged on. At the earlier stages of the consolidation process, their impact was compensated for by making the wing base narrower, i.e. the transverse braces between supporting axes shorter and thence stronger. Yet, based on that, this should have resulted in a restricted deformability of the region involved because of longitudinal veinal trunks being drawn together. To prevent this, some axial supporting elements (CuP and 1A bases) were reduced; some others changed their position (R superimposed on M) while the remainder (M and CuA bases) was modified into a brace between the supports of the remigium and clavus, this brace being both readily deformable and reliable. A shortened arculus became what alone limited the movability of the cubital bar relative to the main mechanic axis of the wing during folding, simultaneously preventing the wing regions proximal to arc from being penetrated by the remigial furrow. Secondly, a higher beat frequency if not amplitude could have hardly been achieved without the wing being consolidated. Among the above adaptations, only the consolidation of the area around the claval furrow base, which resulted in reduced bases of CuP and 1A, seems to have been in no way involved in folding. Yet the other adaptations were complex, implicating both wing functions which thus had to be optimized through an adaptive compromise (Rasnitsyn, 1986, 1987). The main effect of these adaptations was a reinforced but easily deformable wing support which at bottom had two ultimate trunks of the remigium, the radial and cubital bars. Ending in the radial or oblong cell and linked by “r–m”, these axes changed their relative position during folding/ unfolding while remaining hard enough to support the wing during flight. Further evolution within the caraboid venation type produced a few special modifications. In Adephaga and Myxophaga, the radial bar developed into the costal bar while the simple anal arculus was involved in a complex one (anarc.c.) as a particular basal brace between the remigium and clavus. The presence of

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only a secondary base of CuP can be considered as a synapomorphy or perhaps homoplasy of Archostemata + Polyphaga. The complex arculus (arc.c.) resulting from the MA+MP base merged into arc is certainly a homoplasy of Cupedidae, Archostemata, and Polyphaga but Scirtoidea. The absence both of a vein-like RP1+2 and the oblong cell (this has also been lost by numerous Carabidae through evolution, but retained in some Clambidae and Sikhotealinia), as well as membrane sclerotizations, including secondary veins, involved in wing support, is a venational distinction of Polyphaga. There are also differences between the suborders in the combination of costal and cubital joints and bending zones. The joints cj and cuj occur combined in Archostemata. The Adephaga and the Myxophaga each displays a combination of cbz and cuj. The Polyphaga is distinctive in having weak to indistinct cbz and cubz combined; stronger bending zones are secondary while cj or cj plus cuj only occur exceptionally (Scirtoidea). However, the most peculiar venation pattern is known to have been that of extinct schizophoroid archostematans (Fig. 19). Its main and prominent distinction was the carpal cell of unusual shape, very short and oblique posterodistad. This apparently resulted from the RP base reduced in length until lost, with the RP+MA base released from being intersected by field B. The evolution of the beetle wing entered the next stage since the cantharoid venation type was formed (Fig. 21). It differs from the caraboid one by the following characters: (1) the costal bar substituted for the radial bar, (2) the recurrent “radius” (“Rr”) well-developed, (3) no cross-veins in the remigium due to the carpal cell open basally, (4) only one, always weak, apical veinal branch, MP3+4, in the apical membrane, (5) Cur present because of the CuP base reduced. These features are followed by (6), a prominent tendency towards only extreme two supporting axes persisting in the remigium. There are two main distinctions of this type: (7) the oblong cell absent as probably already reduced within the caraboid venation type and (8), the presence of secondary supporting structures, “veins” and sclerotizations, which constitute a particular sclerotization pattern of the apical membrane. The above venation type underlies the wings of all of the Polyphaga but Scirtoidea. It stemmed from a new way of folding and started developing after the costal bar had been formed and the oblong cell perhaps lost. Fields B and A tended to strongly decline after the transverse folding had been shifted beyond the remigium basal part. The smaller the fields, the weaker the deformations of the costal, medial and cubital bars. Based on this, veinal joints, strong bending zones, the radial cell as a firm supporting unit, the internal border of the carpal cell and the basal section of the medial bar became increasingly redundant. Bending zones were reduced to very weak ones, joints/breaks if any were restored to normal veinal sections while the medial bar evolved into the recurrent media

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(Mr) which shortened progressively. The radial cell got smaller, chiefly narrower, while the RP+MA base, perhaps combined with m3, was transformed into “Rr”. The above groundplan largely evolved along further two directions. Following the first, the staphylinoid venation type emerged from the pattern of which a movable CuA2 was characteristic. Occurring in Staphyliniformia alone, it was developed in parallel in histeroids, Scarabaeoidea and Staphylinoidea through the execution of all or most of the following modifications: (1) a considerably to strongly shortened and usually also attenuated basal part of the remigium, (2) accordingly, a longer apical membrane reinforced with vein-like and often multiplied sclerotized strips secondary in nature, (3) a partially to completely reduced rc and often also Mr, (4) a partly reduced venation in the clavus following both 2a and the CuP distal section reduced. The second direction has led to manifold variants which can be included in the reduced cantharoid venation type. It is linked by transitions with the cantharoid type; hence, it can only be defined by a combination of evolutionary trends. Among them, the principal are as follows: (1) reduction of both the radial cell and “Rr” the cell is associated with, (2) progressive reduction of Mr, (3) incorporation of rc and Mr remnants into “r–m”, (4) stepwise, up to a complete reduction of veins in the clavus and jugum. This type predominantly occurs in small-sized Cucujiformia, especially Cucujoidea and Tenebrionoidea, distinctive in having a fairly short apical wing membrane and thence a not or weakly specialized folding pattern of the “clavicorn”, “serricorn” or “eudryopiform” subtype. The above tendencies are in part conformable to those underlying the staphylinoid venation type. As the remainder of the latter tendencies near completion, namely, those towards a movable CuA2 and a very long apical membrane reinforced with secondary “veins”, the reduced cantharoid venation type increasingly approaches the staphylinoid one. The wings of Jacobsoniidae, Ciidae, numerous Cucujoidea (Corylophidae, Propalticidae, Cryptophagidae, Nitidulidae) and most of Curculionoidea (Curculionidae, Brentidae, etc.) are the most characteristic members of this, pseudostaphylinoid, venation type. Venation patterns of the wings which do not fold transversely (those of some Buprestidae, Lymexilidae, Rhipiphoridae) deserve to be placed in a separate group. They converged as developed, albeit emerged from very different venational groundplans within the cantharoid venation type. Homoplasies resultant from this are as follows: a strongly costalized wing due to a very narrow remigium, with the radial cell strongly attenuated to reduced; the costal bar secondarily extended apicad; the strictly axial orientations of the longitudinal veins, as well as sclerotized strips of the apical membrane, especially aas–pcas; a tendency towards reduced cross-veins in the clavus, those of one or both anal cells included.

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The evolution of venation in the clavus plus jugum requires special attention. The groundplan (Fig. 15) very closely resembles certain chauliodine venations (Fig. 12), especially in the region around the jugal fold base (cf. Figs 24–27). The groundplan pattern is defined by seven apical veinal branches, five in the clavus (entire CuP, AA1+2, AA3a', AAP, AP3a) and two in the jugal lobe (an apically shortened AP3b, AP4), the cross-vein cu–a2, at least traces of the anal arculus, two anal cells (1a and 2a), the AP3a base and the axial cord which is well-developed at least in the jugum. The patterns closest to the above one are only present in the most primitive beetles, i.e. Archostemata, Adephaga and Scirtoidea, with some plesiomorphies having been replaced by apomorphies due to character transgressions. These derived characters are as follows: rather strongly reduced AP3b and the AP3a base (Cupedidae, Archostemata), only four veinal apical branches in the clavus (Adephaga or Scirtoidea) and a desclerotized base of AP3a (Scirtoidea). The main trend in the evolution of the groundplan involved (Fig. 44) lay in simplification through successive reductions of the following integrants: (1) the axial cord, AP3b and the AP3a base, (2) the CuP secondary base, (3) cu–a2

a

b

c

d

e

f

g Figure 44. Evolution of the wing venation of the clavus; a–g, successive stages. Dashed to dotted lines correspond to rudimentary or reduced veins.

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resulting from AA1+2 shifted onto CuP, (4) a free distal section of CuP, (5) the AA1+2 base through AA3a' shifting onto CuP+AA1+2. As a rule, stages (4) and (5) concurred with (6), reduction of 2a. At different, mostly final stages, (7) the clavus’ venation became detached from CuA after either cu2 or the CuP basal part, or, more often, both had been reduced. The process was terminated by (8), AP3a progressively shortened from the apex until completely obliterated, (9) 1a open, and (10) all apical veinal branches but AAP reduced. As the jugum’s support, AP4 declined stepwise either through shortening from the apex and/or by means of desclerotization. Yet AP4 had remained traceable until the venation of the clavus plus jugum or the jugal lobe alone was totally gone, as a rule. Thus, longitudinal veins as axial supporting elements of the wing trailing area were reduced in succession. This oligomerization was a staged process. In its course, posterior apical veinal branches stepwise substituted for the anterior ones and became separated from one another, as well as from the remigium’s support (CuA). Many of the above alterations occurred in different beetle groups in parallel, the taxonomic rank of these varying from suborder to genus-group. The reduction process was considerably accelerated by adult miniaturization. This led the venation patterns of miniature beetles to almost or even entirely reduced, in part due to the clavus and, especially, jugum strongly to completely obliterate. To summarize, one comes to the following conclusions. The venation of the beetle hind wing emerged from a primitive venational groundplan shared by all endopterygotes, but was apparently the closest to that of Myrmeleontidea, especially Megaloptera (Figs 12–14) . From that of the latter group, it is distinguished by an apotypic character set, thus giving evidence for the entire wing support, as well as some of its constituent parts, being strongly specialized. The wing apex was released from veins, together with axial supporting structures consolidated and oligomerized, including braces in between. This, coupled with structural modifications which contributed much to the flexibility of these structures, seems to have lightened the beetle wing and adapted its support the best to the alternation of flight function and transverse folding, the latter a novelty. Many veins from the groundplan set were transformed so deeply that not veins proper but structures of high complexity started serving as the main supporting elements in beetle wings. It is the complex and largely negative impact of a strong incline in the beetles towards wing posteromotorism upon the venational groundplan that gave rise to such a wing support. In affecting the wing both directly (through an increased wing-loading) and indirectly (by means of a new, folding function), it intensified certain morphogeneses, including those aimed at consolidating numerous supporting elements. The caraboid and cantharoid venation types sharply contrast in the characters of the remigium’s basal part, but not in those of the clavus plus jugum. The

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supporting system of these two wing regions evolved towards an increasingly reduced venation pattern. This was developed in the course of successive reductions of certain integrants, such as apical veinal branches, anal cells, etc., these evolutionary changes in no way being correlated with venational transformations outside the regions involved. That these changes must have been sharp, almost saltatory, in the remigium, versus slow in the clavus plus jugum, has functional explanations. It is certain that the two wing regions differ from each other by the number, intensity and character of functions they perform and, consequently, by the extent to which the respective support is specialized and thus liable to evolutionary change. That the venation is less specialized in the clavus plus jugum follows from its minimum contribution both to folding and flight apparatus. The remigium’s support is in contrast highly specialized, being responsible for both wing functions: it is the remigium that the support of the leading edge and almost all of the integrants of the folding pattern are confined to. For that reason, this is what keeps the venation of the remigium very stable in the course of wing historical development. Evolutionary conflicts between flight and folding functions of the wing support contribute not less if not more to this stability. This requires the functions to be compromised, thus restricting potential constructive solutions to any particular evolutionary problem to a few available ones. At a certain stage, a new important evolutionary factor, the size evolution of the adult, was added to the other ones. Among its opposite trends, miniaturization was much more significant. It affected wing venation both directly and indirectly through the wing folding apparatus. The miniaturization trend must have intensified numerous reduction processes, culminating in strongly reduced wing venation patterns in extremely small-sized beetles.

The wing as a whole As follows from the above, the evolution of the beetle wing support, especially venation, and folding pattern was staged, each of the two main stages naturally corresponding to a particular structural pattern, or morphological type. Table 2 shows that the primitive, archostematan folding pattern is always combined with the caraboid venation type, whereas the advanced, polyphagan folding pattern reaches beyond the cantharoid venation, being coupled with the caraboid one in Scirtoidea. This disagreement argues that wing venation was more conservative during evolution than the folding pattern and implies it is the latter’s historical development that defined the peculiarities of beetle wing venation.

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Table 2. Distribution of venational, folding and wing groundplans among Coleoptera Suborder

Type/subtype Venation

Wing

Folding pattern Morphological Morphofunctional

Adephaga + Archostemata Polyphaga Myxophaga Scirtoidea Polyphaga but Scirtoidea caraboid archostematan adephagan cupedid archostematan adephagan cupedid archostematan adephagan cupedid

cantharoid polyphagan scirtoid “clavicorn” polyphagan scirtoid “cantharoid” scirtoid

“cantharoid”

Morphological and morphofunctional types The archostematan wing type is basic for Recent Coleoptera and combines plesiomorphies of the adephagan and cupedid subtypes (Figs 17 and 18, respectively). The wing is wide or moderately wide, with a rather short apical membrane, a long and wide clavus, a wide jugum, but without jugal incision. In a folded wing, the radial and cubital bars are strongly deformed just proximal to the radial and oblong cells, respectively, while the wing apex is more or less distinctly rolled (Fig. 45). The major functional elements of the folding system are cpp and cp due to a combination of large fields B, A and G, and an almost non-differentiated apical folding sector distal to CuA2. Venation is of the caraboid type: rc, the oblong cell and the carpal cell are well-developed, pst is fairly large, the medial bar is entire, the arculus is simple; m3, rms, the CuP primary base, anarc, the AP3–AP3b–AP3a association, the entire (long) axial cord and cu–a2 are present; apical veinal branches are four (RP1+2, MP3+4, CuA1 and CuA2) in the remigium and five in the clavus; neither secondary veins nor sclerotization patches are observed in the apical membrane. An increased wing loading and the development of a folding pattern were the main evolutionary factors that seem to have directly affected the beetle hind wing as the present wing type was formed. Both were ultimate links in a rather trivial causal chain (Fig. 48), in which the first link was intensification of the protective function of the fore wing. As this process advanced, it was accompanied by a progressive sclerotization of body integuments if not having given rise to it. Because long elytra and a much shorter abdomen fitted in with each other not too well, they contributed the least to the protective construction they constituted.

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a

b

c

d

Figure 45. Folding of the left wing of Tenomerga, Cupedidae, Archostemata, schematically; a–d, successive stages. Solid and ordinary lines correspond to convex and concave folds, respectively.

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So they had to coadapt until becoming subequally long (Fig. 49). As a result, the elytra grew shorter while the abdomen might have become a little longer. It is likely these changes, not the wing’s working area enlarged as a way to reduce the wing loading upon the hind wing (Grodnitsky, 1996), that made the hind wings longer than the elytra and thence folding the hind wing necessary. At least in the earliest beetles such as Tshekardocoleidae (Fig. 49b) which were sometimes placed in a suborder of their own (Crowson, 1975) or, together with other Permian beetles (Taldycupedidae, Asiocoleidae, Permocupedidae and Rhombocoleidae), in the separate order Protocoleoptera (Kukalová-Peck, 1991), the hind wings failed to exceed the elytra in length. The elytra remained much longer than the abdomen, therefore the hind wings were either not folded yet (Kukalová-Peck & Lawrence, 1993) or perhaps folded only lengthwise (Haas, 1998). I doubt the latter was the case because beetle wing folding is such that it could only start forming either with its two components combined, i.e. transverse and longitudinal ones, or with the latter component following the former, not otherwise. Hence, it seems better to relate longitudinal folds found in the hind wings of Sylvacoleus to an incipient transverse folding. This process could have easily been initiated by change in fore wing shape, resulting from the wing apex shifted caudad as the fore wing was modified into an elytron. This was followed by the formation of a long and pointed apex shared by the folded elytra which were contiguous throughout their posterior edges, now the elytral suture (Fig. 49b). Such a protective construction could provide earlier beetles with a few adaptive advantages. These were (1) the protection of a rigid and strongly protruding ovipositor and (2) a general consolidation of the entire protective construction resulting from more tightly interlocked elytra, with their prominent parts in the form of elytral apices reduced from two to only one. As the elytral apices approached each other, the side (costal) margin of either elytron bent sharper at the apex, thus giving rise to the respective bend in the hind wing. What made this primitively weak bending zone still sharper was a gradual shift forward of the shared elytral apex (Fig. 49c). Since it began to form, the veinal trunks at the anterior wing margin, first the subcosta and radius, were involved in a transverse folding apparatus. It remains unclear whether these trunks were initially springy or not. If yes, then a mechanism had to be developed to prevent the hind wing from unfolding spontaneously. In a thus folded wing, numerous irregular folds radiated from about the middle of R–RA. Two large triangular fields B and A arose through these folds’ differentiation. The fields affected wing support dually, but chiefly negatively, making veins weaker where these were intersected. Since the veins adjacent to field B folds constituted the outer carcass of the carpal cell, they tended to

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rim these folds to strictly localize them. This could change the orientation of RP3+4+MA and thus precondition its fusion with the veinal branches caudal to it. The above way of folding required the wing support to be consolidated where impaired by this folding. The requirement was considerably strengthened by the flight function of the hind wing intensified through increased amplitudes and beat frequencies to compensate for the anterior flight motor in decline. Longitudinal veinal trunks reduced in number, their bases shortened and transformed and the arculus shortened, consolidated the wing base, including the area around the claval furrow. A partial fusion between the posterior branch of RP+MA and the anterior branch of MP left a distal transverse brace between the leading edge support and supporting axes caudal to it simpler (morphologically shorter), thence more secure. This new brace took the appearance of “r–m” bearing the radiomedial spur as conformable to the shared base of the fused veins. The consolidation process was accompanied by adapting the wing support to folding through specialization of its separate elements (veins) or their parts, as well as through the formation of complex structures of higher deformability, such as, e.g., the radial bar. The above transformations resulted in a wing with a firm but flexible support of the remigium which was well-adapted to strong folding deformations. More specifically, field B was equipped with its own supporting carcass in the form of the carpal cell. As the region of the maximum folding deformations, the apical membrane became capable of folding easily, having been relieved from normally developed veins. The radial and cubital bending zones or joints became the devices for areas Q and W to readily rotate upon the respective pivots (Figs 41a, 45, 50a). To support these areas during folding or unfolding, the radial and oblong cells evolved into reinforced supporting units. Supporting axes differentiated: the radial (costal) and cubital bars became the main among them. Further evolution of the archostematan wing type proceeded in the format of special modifications and was largely aimed at an improved folding pattern. Among the modifications which occurred, the most specialized was the schizophoroid wing (sub)type (Fig. 19) peculiar to extinct schizophoroid archostematans (Schizophoridae, Catiniidae). Its characteristic was the minimum folding deformations of the leading edge support. This emerged from a reduced proximal costal pivot resultant from field B in considerable decline. Both RP+MA and the radial cell incorporated into a rigid supporting unit was an additional effect. The cupedid wing (sub)type (Fig. 18) covers Recent Archostemata. The folding pattern has survived close to the groundplan, with many primary venational elements or their rudiments (m3, m–cu2, MP1+2 base, axial cord) traceable, including those absent from the other beetle wings. The regular apical roll might be a secondary modification in the folding pattern which, together with

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shortened and broadened radial and oblong cells, an obliterated radiomedial spur, a strongly reduced pterostigma and a well-developed costal joint, was an adaptation to an improved folding of the wing apex. The only persisted complex arculus and secondary base of CuP are among the other significant novelties. The adephagan wing (sub)type (Fig. 17) was developed from a complex adaptation to the stronger reduction of a very long wing apex during folding. Particular adaptations in this direction were as follows: (1) the costal bar corrugated throughout its length to receive additional flexibility and (2) CuA2 movable. These basic adaptations were followed or in part accompanied by additional ones, among them neither CuA2 nor veins retained inside the carpal cell. The clavus’ venation was only slightly modified by losing one of the apical veinal branches, probably AA3a'. Except for these apomorphies, the adephagan wing type is not less if not more primitive than the cupedid one. A very long wing apex deflected in the folded wing, a large pst, the simple arculus (mp–cua), a rudimentary but still traceable MA basal section, the entire axial cord, the CuP primary base and a survived rms, as well as a more or less distinct AP3b, together with the AP3 and AP3a bases, provide evidence for this to have been the case. The presence of the anarc.c. bracing basal sections of CuA and AA3 could be considered a plesiomorphy as well. The wings of Myxophaga fit in well with this wing type. It is distinctive in nothing else but derived characters. Most of them seem to have resulted from the extremely small-sized body peculiar to all Myxophaga. On the contrary, the wings of Adephaga have not been so deeply influenced by size evolution. The beetle wing entered the next evolutionary stage since the polyphagan wing type (Fig. 20) emerged from differentiation of the apical folding sector. As a result, two closed triangular fields, C and S, were formed while the field D started developing. When still open, the field D shared the same function with the field B and only initiated a redistribution of this function among them. Hence, the field B or its derivatives played the leading role in folding until D was open. The way of folding thus generally survived almost the same as in the cupedid wing type, differing chiefly by the wing apex folding flat (Fig. 41b). Correspondingly, wing venation persisted nearly unchanged, caraboid, being composed of the carpal cell, the RP base, m3, the RP+MA section between r1 and m3, rms, AP3–AP3b, the axial cord, the entire medial bar (M–MP–MP3+4), the proximal costal and cubital pivots and the respective veinal joints, all apical veinal branches in the clavus, a distinct cu–a2 and the oblong cell (Calyptomerus, Clambidae; Sikhotealinia, Jurodidae); apparently, the costal bar had not substituted for the radial bar yet. Among venational apomorphies, some are shared with Archostemata (no RP+MA base and an almost totally reduced pst), whereas some others are de-

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rived from those of Archostemata, among them both CuA1 and the CuP secondary base reduced and RP1+2 seated on the radial cell1, but reduced distally, thus forming the radial spur (rsp). The RP1+2 distal section might have been involved in the sclerotization pattern of the apical membrane. This character can be regarded either as plesiomorphous or apomorphous, depending on the approach used: the former case implies complete or a partial conformity between the sclerotization and venation groundplans, whereas the latter emphasizes a secondary nature of sclerotization, be it membrane in origin or a venational transformation. This wing type is the groundplan of Polyphaga. It combines plesiomorphies of Jurodidae, Scirtoidea, Elateriformia and Cucujiformia, the best corresponding to the wings of Scirtoidea. These are placed here in the particular scirtoid wing (sub)type, being distinguishable from the above groundplan by a few derived characters, as follows: the field B divided into 2-3 daughter fields, one apical veinal branch lacking in the clavus, and the cross-vein cu–a2 reduced. The scirtoid wing type is nevertheless barely different from the cupedid one in general folding characteristics but apical folding. This allows to include it in the archostematan morphofunctional type (Tab. 2). The wings of the other Polyphaga, Jurodidae included, belong to the “cantharoid” wing (sub)type. This is derivable from the polyphagan wing type (Fig. 21) and likely to have stemmed from it directly, resulting from the transverse folding component carried outside the wing basal part following field D substituted for B functionally. The decline in the field B having made all the field association B–A–G less functional and thence considerably reduced in size (Figs 46 and 47) together with the proximal costal and cubital pivots, the areas Q and W became either much less movable than before or immovable at all (Figs 41c–h). The costal and cubital bars grew more rigid since the costal and cubital joints/breaks had been restored to normal veinal sections. Accordingly, the internal support of the remigium composed of the carpal cell and the mediocubital loop combined became unnecessary. This cell opened internally while the medial bar was transformed into the recurrent media, this tending to be increasingly short off the base. For the same reason, rigid supporting units of formerly a large radial or oblong cell became useless. Shortening the rc brought m3 to being reduced or involved in the “recurrent radius” (RP+MA basal section). Some other tendencies followed, 1

This character may be uncharacteristic of Scirtoidea as stemming from elongating and narrowing the rc at a later evolutionary stage. If so, then a short and free distal section of RP+MA could supposedly have only been either involved in the rc posterior border or reduced in Scirtoidea.

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a

b

c

d Figure 46. Folding of the left wing of Dacne, Erotylidae, Polyphaga, schematically; a–d, successive stages. Arbitrary designations and symbols as in Fig. 46.

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a

b

c

d

Figure 47. Folding of the left wing of Platycis, Lycidae, Polyphaga, schematically; a–d, successive stages. Same symbols as in Figs 45–46.

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among them those towards reducing rms, anarc.c., the axial cord and rc; the latter was reduced in size or open. Evolution of the morphofunctional organization of the hind wing in the Coleoptera could be suggested as follows. Pterygote folding wings seem to be of similar organization. There are two functional apparatus in such a wing, one flight, the other folding, each performing the respective alternating function. Almost all of the structural elements of the alar area are involved in the former apparatus which is major. The latter apparatus is auxiliary and includes only the jugal fold, as well as the bases of some veinal trunks (Brodsky, 1988). That the beetles became capable of folding their wings transversely resulted in a strong increase in the folding function, as well as in a higher complexity

Figure 48. Earlier development of the hind wing folding apparatus – factor and event relationships.

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a

b

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c

Figure 49. Hypothetical evolutionary stages (a–c) of the Coleoptera hind wing folding apparatus: a, no transverse folding (the ancestor of Coleoptera: the fore and hind wings subequally long, both extended far beyond the abdominal apex; when adducted to the body, the fore wings separate); b, a weak basal transverse folding (?Tshekardocoleidae, Archostemata: the fore and hind wings as above, but when adducted to the body, dorsally flattened fore wings, now the elytra, contiguous along the suture); c, a strong basal transverse folding (Adephaga and Myxophaga: the hind wings considerably longer than elytra; when interlocked along the suture, the latter as long as the abdomen). The diagram is based on the illustrated reconstruction of Sylvacoleus admirandus Ponomarenko 1969 (from Ponomarenko, 1969: fig. 29b).

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f

a

g b

h c

i d j

e k

Figure 50. Topological relationships between immovable (white), less movable (light grey) and movable (grey) regions of the Coleoptera hind wing plate. Wing types: cupedid (a), scirtoid (b), cantharoid (c–e, g–k), adephagan (f). Folding patterns: cupedid, Cupedidae (a), scirtoid, Eucinetidae (b), “clavicorn”, Chrysomelidae (c), “dryopiform”, Endomychidae (d) and Curculionidae (i), “elaterid/serricorn”, Omalisidae (e), adephagan, Carabidae (f), hydrophiloid, Hydrophilidae (g), agyrtid, Agyrtidae (h), nitidulid, Nitidulidae (j), malachiinae, Malachius, Melyridae (k).

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both of the folding apparatus and morphofunctional organization of the entire hind wing. The folding apparatus largely developed in the remigium: it is in this wing region that the folding pattern evolved, with its own supporting system formed from the supporting system of the flight apparatus. The origin of a new and rather intense function of transverse folding accelerated the functional and thence morphological differentiation between the integrants of the folding pattern, especially the supporting system shared among both functional apparatus. That the apical folding sector occupied a greater part of the wing apex and was rich in folds of unstable position caused remigium subdivision into two parts sharply contrasting in strength properties. Of them, the apical membrane became the region of a supporting hypofunction. The remigium basal part, on the contrary, took the maximum supporting function, thus becoming the body of wing support. Yet this general reinforcement of the remigium’s support could hardly have been attainable without a compromised increase in flexibility (at the expense of rigidity) of at least some of the supporting elements. This is sure to have been necessary for the wing to resist the strong folding deformations occurring in the wing region where the field association B–A was situated, this being the main functional unit of the folding pattern. Elimination of this disagreement by the development of the remigium support as a bifunctional structure seems to have been the main evolutionary trend at this evolutionary stage. The “cantharoid” wing type having been developed, the above morphofunctional organization of the alar area transformed profoundly. The functional substitution of the C–S–D field association for the B–A association almost released the support of the remigium basal part from the folding process, especially transverse folding. The supporting structures that were formerly involved in both functional apparatus, i.e. flight and folding, prove to have only been involved in the latter. The remaining supporting elements predominantly serving for folding were lost as unnecessary. The main effect of this was a weaker cohesion between the integrants (functional apparatus) inside the whole (wing), further resulting in a far more independent development of both. All above appears to have lowered the level of the adaptive compromise (Rasnitsyn, 1986, 1987), from which a great variety of derivations of the “cantharoid” wing type have originated, these often being quite dissimilar to what have given their rise. Yet these differences revealed themselves afterwards, as the wings diversified affected by size evolution and the consequent development of a folding pattern. Many wing characters appeared in different beetle groups in parallel, resulting in a considerable similarity between their members in wing structure. The following functional wing types arisen from the main evolutionary trends realized will illustrate this similarity.

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The main evolutionary trends and functional wing types (1) The “serricorn” wing type covers the wings with the nominate folding pattern and its analogues from the elateroid folding type. Apparently, it emerged only from the development of the folding pattern (Figs 41g, 47, 50e). The trend towards a strongly elongated field C, with considerably to completely reduced fields B and A for accompaniment, resulted in the least folding deformations in the remigium basal part and an almost eliminated folding deformation of the costal bar. The anterior fold of the field C, cq, became strongly involved in flight as the remigial furrow. The present type was developed in numerous Elateroidea, Tenebrionoidea and some Cucujoidea (Cucujidae, Passandridae, some Silvanidae and Erotylidae), all these beetles showing a larger body or longer elytra. Therefore, the above features are combined with a short apical membrane and entire or barely reduced venation of a large clavus plus jugum. Secondary modifications are a more or less narrow and long rc, as well as a longitudinal “Rr” if any. (2) The wing non-folding transversely occurs in some representatives of Buprestidae, Lymexilidae and Rhipiphoridae, in which the wings in resting position do not extend beyond the abdominal apex, being non-reducible in length. In such a wing, either the folding pattern is totally reduced or only a lengthwise and more or less fan-like folding takes place, with the jugal lobe always surviving tucked. Such a wing tends to be strongly costalized, with cross-veins reduced. This wing type is observed in larger or medium-sized beetles, with shortened elytra as well. It appears to have emerged not through size evolution but by adapting the wing to flight with higher beat frequency. Similar wing structure is observed in the Telegeusidae (Forbes, 1926; Wallace & Fox, 1980), whereas its close allies, Phengodes, Phengodidae (Wallace & Fox, 1980), and some Cantharidae, as well as some Cerambycidae (e.g. Molorchus, Necydalis), do not fit in with this wing type, albeit distinctive in very short elytra. (3) Wings with a very long apical membrane. The longer the wing, the much longer its apical membrane. This makes it necessary to appropriately fold the wing apex. Coleoptera found several ways, separate or combined, to solve this problem. Among them, the first was an increasingly long deflected wing apex through making the cubital spur (CuA2) movable or reduced. As a result, the posterodistal portions of the areas W and V were involved in the field H (Figs 50f–k). This adaptation seems to have been primary for Adephaga, Staphyliniformia and Nitidulidae. In all other cases it accompanied either infancies (Figs A: 30, 198–200) or further developments (Figs 50i; A219–224) of the “dryopiform” folding pattern. The latter also holds true for the malachiine folding pattern (Figs 50k; A236). Other Coleoptera used this pathway either rarely or incompletely.

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Subequally long costal and cubital supporting axes seem to have been necessary for this adaptation to reach completion. When longer, the costal axis was equipped with devices, primarily the bending zone, which enabled the axis to deflect more strongly. These bending zones could be either primary (Fig. 50f) or secondary (Fig. 50k). When a longer and rigid costal bar (or its secondary elongation) occurred, the fold hw had to intersect CuA2 distal to its base (Figs 50h, j). The development of the “eudryopiform” folding pattern, with its further evolution into the “postdryopiform” one, was the second pathway (Figs 41d–f, d–h). This evolved by some Hydrophiloidea, Byrrhoidea and Tenebrionoidea (Mycetophagidae, Archeocrypticidae, Ciidae, certain Tenebrionidae), as well as numerous Cucujoidea, Derodontoidea and almost all of the Curculionoidea. At last, the third pathway was peculiar to Bostrichoidea (various patterns of the bostrichoid folding type). The remaining Polyphaga have solved the problem without growing out of the “clavicorn” folding type. The impact of an advanced folding pattern on the wing support depends on the pattern’s peculiarities. It is negligible to null for the “eudryopiform” pattern (cf. Figs 50c and d) because this emerges from structural modifications occurring in the apical membrane alone, i.e. outside the wing support. Rudimentary veins and secondary “veins” of the apical membrane undergo no significant changes in this case, but the sclerotizations supporting the fields S, D and R sometimes get reinforced. As the “eudryopiform” and, especially, “hemidryopiform” folding patterns develop, they grow to more strongly influence upon the supporting elements. In particular, the apex of the costal axis detaches from the wing margin or dilates adequately as the distal costal pivot gets increasingly internal (Figs A: 152, 164, 165). The fan-folding wing of Staphyliniformia (Scarabaeoidea; some Hydrophiloidea and Staphylinoidea) appears to have been an evolutionary response to elongating the apical membrane, too. Its development was determined by the following character combination: the distal costal pivot modified into a reinforced apical joint, a movable CuA2, the apical membrane reinforced with membrane crimping, the subequally large fields D and S with a nearly lengthwise fold sd in between, and a rather strongly reduced venation in the clavus. Shape changes in fields D and S, as well as transformations of membrane crimping into secondary “veins” to support the apical membrane completed the formation of the present wing type. This having been made, further elongation of the apical membrane relative to the wing basal part became possible. Except for a longer wing apex deflected during folding, the fan-folding wing seems to have got an additional advantage defined by accelerating if not the folding then unfolding of the wing. Some staphyliniform beetles appear

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to have lost this advantage in exchange for a reinforced support of the leading edge. The former alteration was due to a generally simplified folding pattern, culminating in the apical joint replaced with a tertiary apical hinge lying distal to pstII. As a result, the costal bar became longer through its immediate extension into pstII. This wing then evolved into the plumose one (Fig. A65), which folded only transversely and was equipped with a highly modified venation in support. The evolutionary tendency towards a longer apical membrane had one more effect for the wing folding apparatus. This incorporated such extrinsic morphological structures as the abdomen. In the course of evolution, its tergites were equipped with spiculate binding patches to better manipulate the wing apex during folding. This is likely due to the supporting structures of the remigium more or less contributing to only self-folding the wing. Toward the apex the effect declines until it ceases in the regions of the fields S and D or R and H, self-folding in the latter region being already hampered. A residual impulse of the folding fields seems to suffice for folding a fairly short apical membrane, whereas a very long apical membrane supplied with numerous or longer folds is not only incapable of self-folding, but inhibits the entire folding process. Except for beetles with very short elytra (like e.g. Staphylinidae) and thence showing a folding pattern of high complexity, the contribution of the abdomen to the wing folding apparatus seems to be especially substantial in the wings of the bostrichoid type and folding pattern (Figs A113–124). The most characteristic features of this wing type are as follows: (1) the costal bar reinforced and equipped with a strong secondary bending zone, (2) a strongly to completely reduced field A, (3) a large and transverse field B, and (4) fields of the central group, C, S, D, R and H, fused with one another in different combinations. In such a wing, the apical sections of the costal and, especially, cubital bars are strongly deformed during folding while the basal sections of these supporting axes remain immovable or almost so. All of these peculiarities, the latter particularly, must either strongly hamper self-folding or even make it impossible for a so constructed wing; therefore, the abdomen does constitute an integral and essential part of the wing folding apparatus. Besides this, the abdomen operates during folding the wing as if it sets the springs of the costal and cubital bars such that these springs could release themselves automatically and thus trigger off the unfolding of the wing. Among all above functional wing types, each is distinguishable by a particular folding pattern. Yet in most of these cases a modified folding pattern seems to have been only intermediary, whereas the source of all transformations of the wing was elongation both of the wing and its apical membrane, either resulting from adult miniaturization as an evolutionary trend.

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Size evolution of the imago Beetles strongly vary both in size and shape, this substantially affecting their wings. As evolutionary factors, changes in body size or shape can give similar results for wing structure. More specifically, the effects of a stouter or smaller body are often comparable. The same holds true for longer elytra or a larger body. The following general trend is well-visible: the smaller the body, the relatively longer the wing (Hammond, 1979; Haas, 1998), and the much longer the apical membrane of the wing (Fig. 51; Haas, 1998). What defines these, as well as some other changes seems to lie within flight kinematics. Since the Reynolds number (Re) depends on the dimensions of an object passing through a fluid, insects of decreasing size and/or velocity experience aerodynamic forces in which viscous forces increasingly predominate over inertial forces, and vice versa (Alexander, 1970; Brodsky, 1988). Preventing low Re values is necessary for smaller insects to maintain active flight. Possible solutions are known to be few. Higher wingbeat frequencies are observed more often (Brodsky & Ivanov, 1983; Brodsky, 1988). Extremely smallsized insects require mechanisms of propulsive force generation different from the usual ones, including higher upstroke amplitudes to reach the clap at the upstroke top. Fast rotation mechanisms generating no vortices often substitute for flapping ones in the wings of smaller insects (Grodnitsky & Morozov, 1994). Wings deform in flight more strongly and, conformably, the flexion-lines are better developed in larger insects (Rasnitsyn, 1969) and vice versa (Vogel, 1967; Brodsky, 1981, 1982, 1988). Wing venation contributes accordingly to wing support, being better developed in larger insects than smaller ones. As the body grows smaller, wing venation as the supporting carcass becomes reduced until it is optimal for the wing to supinate in a particular way (Brodsky, 1988). Trend towards adult miniaturization As the wing decreases in size, many of its morphological characteristics change, wing shape, size ratio of remigium to clavus and jugum, the extent to which the jugal lobe is separated from the clavus, length ratio of wing basal part to apical membrane, venation pattern, etc. being among them. Shared tendencies are as follows: (1) towards a longer wing, (2) towards a much longer apical membrane, (3) towards the clavus and jugum reduced in size, (4) towards a reduced venation, and (5) towards a more complex folding pattern. Longer wings tend to have higher moments of inertia and increase the probability that wingtips meet in claps at the turining points of up- and downstrokes. Figure 51 shows that it is the apical membrane that contributes to total wing length increment. This wing region is highly flexible as being relieved from

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veins, whereas the wing basal part is much less deformable and probably heavier besides. Hence, it cannot exceed the elytra in length, for which reason the wing is capable of growing in length chiefly through a superior growth of the apical membrane. In addition, when in use, this might prevent the centre of masses

Figure 51. WL/BL and ML/WL ratios in relation to body length (BL) in Coleoptera. WL, wing length; ML, length of apical membrane. The species measured are marked with an asterisk (*) in Appendix 2, with measurements given in Appendix 3.

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from considerably shifting apicad and impede the growth of inertial forces, thus being favourable to the wing as an organ of flight. The support of a longer apical membrane tends to be modified so that the secondary “veins” grow to dominate which look like membrane gutters; vein MP3+4 becomes desclerotized and tends to reshaping likewise. The trailing area of the wing (clavus plus jugum) gets reduced in size largely due to an elongating apical membrane, this resulting in a conformably shorter wing basal part. A progressive separation of the jugal lobe from the clavus contributes to this reduction. It starts since the jugal incision is distinct. An increasingly deep and broad jugal incision usually precedes a totally reduced jugum (Figs A: 59, 64, 209, 236) and often an also strongly narrowed or reduced clavus (Figs A: 65, 109, 152). As a result, the wing gets increasingly attenuated basad. The maximum wing width shifts closer or distal to the middle of the wing length while the wing apex becomes broader and more strongly rounded, sometimes even rectangular (Fig. A197). Yet no general sharp narrowing of the wing goes on, slenderer wings occurring both in larger and smaller beetles. In miniature beetles, a strong size reduction of the wing width is balanced by a hypertrophied marginal fringe. This predominantly develops along the posterior and, especially, posterobasal wing margins and gradually replaces the wing membrane of the jugal lobe (some Staphylinidae) or the entire wing trailing area (Figs A: 108, 109), the plumose wing of Ptiliidae being a culmination (Fig. A65). The miniaturization trend causes many veins to be reduced, but it differently affects the venation of various wing regions. The impact upon the remigium basal part is the least while that upon the apical membrane and, especially, clavus is the greatest. In the basal part of the remigium, both “Rr” and Mr disappear, “r–m” gets desclerotized to indistinct while the radial cell tends to be transformed into a pigmented patch (Polyphaga). In the Adephaga, the reduction process is decelerated, veins becoming almost indistinct only in extremely small-sized forms (Gehringhia, Carabidae). The major supporting axes, namely, the costal and cubital bars, always persist or even get reinforced up to merged into an incrassate stalk in the smallest beetles (Fig. A65). Veins of the apical membrane become desclerotized stepwise; some of them (Carabidae) lose their bases or disappear. Yet the venation of the clavus undergoes the deepest reduction, the miniaturization trend affecting veins either directly or via the clavus reduced in size. Wing veins get obliterated stepwise, but often in a particular way in different coleopteran taxa. Despite this, the effects of that reduction are similar: a small clavus bears a complex axial support. As a rule, this is a vein not or poorly connected to the cubital bar. It is reinforced basally with the first anal cell and gives not more than three apical branches.

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When survived in the smallest beetles, this support is often reduced to the only longitudinal vein if any. This effect is due to the veins increasingly leaving the supporting function for the wing membrane proper, from which they decline progressively as the imago grows smaller. Miniaturization seems to only intensify differentiation between the supporting elements. It keeps or even reinforces the major of them and leaves the others obliterated. Reductions proceed more rapidly where veins, particularly longitudinal ones, are dense. This appears to result from the veins and membrane sectors in between getting allometrically reduced in width, the former following the latter. Such a wing region overloaded with less functional supporting elements thus becomes less deformable. These extraneous veins are eliminated through oligomerization. This logic is well seen for the area around the claval furrow base in the wings of Adephaga. Hence, such venational plesiomorphies as a distinct or at least traceable CuP primary base and a well-developed anarc.c. occur only in larger adephages. In smaller ones, the former vein is reduced while anarc.c. is either obliterated or strongly shortened. A modification in the folding pattern is an evolutionary response to elongation of the apical membrane. Its main result is the origin of the “dryopiform” folding pattern and its subsequent derivations. These serve for folding the apical membrane which is as long as, or even longer than, the wing basal part. Trend towards adult maximization Growth of the body in size affects wing structure not so strongly as above. The apical membrane remains as long as before or grows shorter, hence the folding occurs unaltered and keeps the folding pattern not or insufficiently modified. Evolution of the “clavicorn” folding pattern into the “serricorn” one is the most frequent modification. The impact of the maximization trend on the wing venation, sclerotization pattern and articular region is often stronger. It results chiefly in reinforced supporting elements such as axillaries, veins and secondary structures. The axillaries and veinal bases associated with them become not only reinforced, but often also larger and of considerably different shape. The veins tend to be more strongly sclerotized, with rudimentary or weaker ones often being partly restored, rms, MP3+4, the “Rr” anterior component, anarc and the CuP secondary base being among them. Besides this, some wing regions, the clavus in particular, become consolidated, as well as the braces between the remigium and clavus: cu–2 or cu2–CuP grows longer while anterior apical veinal branches often shift onto 2a (Hydrophilidae: Hydrophilus and some other genera; Cerambycidae, e.g. Prionus). Large marginal membranous flaps along the costal

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wing margin are sure to also stem from maximization (some Silphidae, Staphylinidae and Scarabaeidae). At the periphery, the wing membrane often becomes corrugated through being densely covered with microfurrows branching apically and entering the wing margin subrectangularly. This crimping is likely to contribute to the elasticity of a fairly thick membrane. Secondary “veins” approach true veins in appearance in being intensively sclerotized. This especially holds true for longitudinal sclerotizations, such as, e.g., the postjugal one which supports the posterobasal wing margin and often braces it with 3Ax (some Dytiscidae, Hydrophilidae and Scarabaeidae, Figs 28 and 30). Stiffened sclerotized strips of some larger Staphyliniformia seem to have been of different origins. A rather weak membrane crimping might have occurred in a fairly long apical membrane of rather small-sized staphyliniform beetles. Some further increase in body size and/or body compaction operated only as a differentiation factor. This caused these or those elements of crimping to be transformed into “veins”. As the body enlarged, these “primary” elements were either strengthened or reduced, or added by “veins” of later origin. Larger beetles are usually distinctive in having a very large, long and wide wing trailing area, always without claval incision.

Conclusion Although the fore wings of neopterans primarily serve as flight organs, they also perform a protective function in respect to hind wings when at rest. Following this, the chief and primary function of the fore wings tends to be reduced in part or, seldom, entirely. A strong intensification of the protective function of the fore wing in the course of Coleoptera evolution has brought their hind wings to being the only flight motor also involved in performing protective functions. Two principal effects followed, i.e. adaptations of the hind wings to posteromotorism and the development of an apparatus responsible for folding the hind wings beneath the elytra to protect them from damage when not in use. The defensive function is one of the main functions of the beetle exoskeleton. Thus, as the fore wing intensifies this function, it becomes an increasingly integral part of body integuments. The consequent decline of the flight function of the elytra enables them to enhance their auxiliary functions, as well as to acquire new ones. This results in different sculptures, colour patterns, modifications in the interlocking mechanism, the development of a sensor apparatus, changes in strength properties, a partial reduction of the elytra. Yet the elytra become relieved from the flight function only since the flight apparatus is non-

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functional owing to flight muscles or hind wing reduced, or since the elytra are strongly reduced in length and thus incapable of generating lift in flight. Since the wing loading increased significantly, combined with the development of transverse folding, the hind wing faced a problem of retaining its morphofunctional integrity. A folding apparatus could hardly develop without a higher deformability of veins or their parts, this diminishing the strength properties of wing support. Numerous folds intersecting the veins emphasized the effect. The organization of the folds into a system by the elimination of some of them, as well as by a strict localization and incorporation of the others into structural units such as fields confined this negative influence to a few wing regions and some veinal sections. This having happened, the wing support and folding pattern evolved interrelated, the former into more flexible, with no or the least loss of rigidity, the latter towards less harmful for the supporting elements, especially axial ones. Evolution of the wing as an integrated whole defined the specificity of the constituent parts of the whole. It made the supporting system, especially venation, bifunctional in general, but invited its parts to differentiation. The venation of the clavus plus jugum was only marginally involved in folding, so remaining monofunctional and thence unspecialized. In contrast, the venation of the remigium specialized in performing both wing functions. These were flight function and that of folding of the wing in resting position, the former being major and primary, the latter a new and actually protective relative to the wing. As a result, veins of the remigium became functionally differentiated: the major of them were strengthened, whereas redundant or less functional veins tended to be gradually reduced. The former veins constituted a supporting carcass of the remigium basal part, which was durable, but easily deformable when necessary. An almost complete release of the apical wing region from normal veins contributed to wing deformability a great deal. This culminated in the remigium subdivided into two regions contrasting sharply in strength properties; the basal part was one such region, the apical membrane the other. But for separate folds or fields only a little contributing to wing support during flight, the folding pattern performs only one function. It often affects wing venation directly by making the veins weaker where intersected by folds or by changing vein orientation. These two peculiarities, i.e. monofunctionality and direct influence upon wing support, together with very simple structures of the constituent parts, left the folding pattern very labile during evolution. In the rate of evolution, the folding pattern was superior to wing venation, thus defining many transformations of the latter. Evolutionary conservatism of wing venation, primarily of the remigium basal part, stemmed from its many elements being strongly specialized in per-

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forming two concurrent and partly conflicting functions. Reaching a compromised organization of the wing support could have only solved this functional and thence evolutionary conflict. The available pathways to this objective were restricted in number. This seems to have decelerated the morphogenetic processes in the region involved and determined its orthogenetic development. The main trend in wing venation evolution was that towards simplification. When necessary, secondary supporting elements, i.e. sclerotization patches or “veins” of membrane origin, replaced obliterated veins. The folding pattern evolved in the opposite direction, towards increased complexity. The beetle wing has passed through two main evolutionary stages. These started with the development of the groundplan of Coleoptera, succeeded by that of Polyphaga. At the first stage, the infancies of wing posteromotorism and folding apparatus seem to have been the main evolutionary factors. As an extrinsic factor, size evolution of the adult was afterwards involved in the evolutionary process. Among its opposite trends, that towards miniaturization was superior. It gave rise to many derived characters and patterns, including cardinal changes in folding patterns and an almost reduced wing venation. The above evolutionary factors affected the wing either separate or combined. The combination of the factors was particular at each stage of evolution, the influence of these or those factors upon one functional apparatus or its part often being mediated by changes in the other apparatus. The archostematan and “cantharoid” morphofunctional wing types differ fundamentally. In the wing of the former kind, the folding and flight apparatus, because of considerably overlapping the supporting systems, constitute a lasting coadaptive ensemble, with only slight deviations from the groundplan through evolution. The development of the “cantharoid” wing type can be considered as an upgrade of the morphofunctional organization both of the entire wing and each of its two functional apparatus. In the folding pattern, new structural elements appeared while a redistribution of functions occurred between these and the newly formed ones. The former supporting system of the folding apparatus was replaced by a new one that was only marginally involved in the flight apparatus. The way of folding altered profoundly, with the region of the greatest transverse deformations of the wing having shifted from the remigium basal part to the apical membrane. An increased rigidity of the resultant main supporting axes could have favoured the wing flight qualities. Finally, the supporting systems of the two wing apparatus grew more autonomous, having been separated. This strongly expanded the adaptive zone for the wing, from which a great variety of derivatives of the “cantharoid” wing type have emerged. A succession of the main wing types through evolution is shown in Figure 52. Many of them are supported not only by synapomorphies, but often also by

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underlying tendencies which defined the development of these or those wing structures. When occurred, parallelisms are usually observed in one or a few wing constituent parts, not the entire wing. As a rule, a great similarity between the wings in some constituent parts, e.g. venation of the remigium, is thus accompanied by more or less strong differences in the others, i.e. the folding pattern or the venation of the clavus, or the sclerotization pattern, etc.

Figure 52. Evolution of the main wing types of Coleoptera. Arrows correspond to the directions of morphogenesis.

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HIND WING STRUCTURE AND EVOLUTION IN PARTICULAR BEETLE GROUPS Adephaga (Figs A1–27) The adephagan wings are almost invariable both in shape and structure. In the groundplan, they are fundamentally different from those of Polyphaga and Archostemata, being similar to the latter in appearance. No representative of the suborder shows the wing quite conformable to the groundplan due to a mosaic of plesiomorphic and apomorphic characters. Articular region. 1Ax with a long posterobasal process. 2Ax normally developed. 3Ax small, more or less straight, with its head slightly curved and distinctly shorter than body of sclerite. A vein-like jugal sclerotization (js) between 3Ax and AP3+4 base fused with vein and then extended to ac base. Dmp entire but subdivided into contiguous BM, BCu and probably also BAA. Pmp sclerites med and cub contiguous; med not adjoining 2Ax, cub as a process of 3Ax. BM and BR separated from each other by a rounded membranous window. Deviations from the groundplan are rather small. In carabids, the 2Ax posterodistal part is reduced (autapomorphy, Fig. 25) while med is separated from cub and sometimes also from BM. 3Ax head is often strongly curved and elongated, thus being perpendicular to, and as long as, the 3Ax body (Hygrobiidae; Dytiscidae: Agabinae, Laccophilinae). Haliplidae, Amphizoidae, Hydroporinae, Dytiscus and Trachypachus show more or less intermediate conditions of 3Ax. The costal bar (cb) strongly varies in length, as well as in the length ratio of its basal (ScP+R) to apical (ScP+RA) sections. Traces of vein fluting, i.e. RA+ superimposed on ScP–, persist as an anterodorsal orientation of the bar in dorsal view. A border is visible between a narrower R–RA and a much broader ScP. C+ScA is weak or rudimentary, usually merged into ScP. Between the RP base and the r1 cross-vein, cb is constricted while RA is much more so and/or either completely or partly desclerotized. During folding, cb strongly curves backwards within cbz while somewhat twisting distal to the RP base or the anterior corner of field B. Thus, in a folded wing, the anterior and posterior edges of the cb distal part are directed ventrad

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and dorsad, respectively. To some but much lesser extent, this twisting extends also over the cb basal part. A small and narrow field Ka (Fig. 53) develops between RA and RP as these draw together during folding. The field is analogous or perhaps partly homologous to the cupedid field K (cf. Figs A4 and A29), this field being the best developed in Haliplidae, rudimentary in Trachypachidae, Noteridae and Rhysodidae or almost indistinct in the remaining Adephaga. A stronger flexibility of cb has been attained through the following adaptations: crimping the cb and its prolongation within pst, combined with attenuating the cb apical part through not only tapering the cb proper, but also desclerotizing a longer or shorter section of RA between RP and r1. Because of this desclerotization, a convex radial fold (rf) develops in centripetal direction during folding. The primary pattern of rf seems to be as follows. The fold rises from between RA and ScP in the anterior part of 1r (Fig. 53), then it goes along over RA and afterwards fuses to the anterior fold of the field Ka (most Adephaga). The following two patterns appear to be derived: (1) rf passes between ScP and a totally desclerotized RA within the 1r cell, then it intersects a short apical section of R, causing its ventral desclerotization, to finally decline gradually basad or perhaps flow into a very long scw (Gyrinidae); (2) rf goes along over a wide RA within the 1r cell, then as a well-developed flexion-line it passes along over a strongly widened R to decline at the border between R and ScP at the cb base. R thus becomes split lengthwise into two parts, frontal and caudal. Of these, the lat-

Figure 53. Structure of the wing region around the proximal costal pivot in Adephaga, schematically.

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ter is more strongly sclerotized at least basally, but often merges into the wing membrane distally (Agabinae, Colymbetinae, Dytiscinae). The radiomedial (rml) and mediocubital (mcl) loops. The width ratio of rml to mcl strongly varies and at least partly depends on wing shape. In the narrower and longer wings, rml more often is as wide as, or narrower than, mcl (Figs A: 8, 12, 15, 17–18, 20, 21). The inverse ratio usually occurs in broader and shorter wings (Figs A: 3–7, 9–11). The pattern is here recognized as groundplan when a more or less longitudinal RP is conspicuously shorter than the vein m1–MA (Figs A: 4, 19, 20). Subequally long m1–MA and RP have emerged either from m1–MA shortened in the course of some general narrowing of the wing and, consequently, either rml (Carabidae, synapomorphy) or RP elongated and more transverse, resulting from an enlarged 1r (synapomorphy of Hydroporinae, Laccophilinae and Copelatinae). Conversely, 1r strongly reduced in size leaves RP strongly shortened (Coptoclavidae, Dytiscidae: Agabinae, Colymbetinae, Dytiscinae, Fig. A8). The latter two modifications seem to have been different adaptations to localize the greatest folding deformations at the proximal costal pivot (cpp). In the first of them, cbz is only confined to 1r, hence its maximum bend occurs far distal to RP while neither rf nor the field Ka penetrates into rml because of a large 1r, with RP long, transverse and rigidly articulated to R–RA. The second modification confines cpp to a very small 1r, a condition which could hardly have been attained without cbz simultaneously extending basad. The choice between the two alternatives might have depended on body size. The latter pattern has only been found in big-sized beetles anyway. The radial cell, or 2nd radial cell (rc, or 2r), and the pterostigma (pst). The pst is primitively strongly sclerotized and separated from an entirely membranous rc by a well-developed RA section (Figs 34a, d; A18–21), with the fold e0 lying just distal to pst. Most of the Adephaga are distinctive in showing a complex pterostigma (pst.c.). This was formed through adjacent, smaller (Figs A: 3, 8, 24–26) to larger (Figs A1–3) areas of rc involved in pst. As then the border (RA) between pst and rc grew weaker to indistinct, pst.c. became an increasingly evenly sclerotized area (Figs 34c, f; A: 7, 12, 23). This is best expressed in miniature beetles, many carabids in particular. In these, a pronounced posterior border of pst.c. lies inside rc open due to its reduced posterobasal border (RP+MA). A shift of the fold e0 basad leaves the portion of pst distal to it and thus invites pst.c. to develop. Sometimes pst.c. emerges from drawing the cross-veins r1 and r2 together (Fig. A22). The beetle pterostigma, either pst or pst.c., mainly serves for a stronger torsion of the wing apex about the leading edge and, consequently, for a more efficient supination of the wing apex (Brackenbury, 1994). Inertial forces play the

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

leading role in this process; therefore, the more proximal and more mesal the pst.c., the stronger the flight deformations involved. A pterostigma either gaining weight due to its strongly sclerotized membrane and the veins it is enclosed with (Cicindelitae) or showing higher movability because of its r2 desclerotized near the middle (Fig. A21) seems to have been among the other adaptations to its higher efficiency. The carpal cell (cc) is primitively polygonal, being angulate at primary vein junctions (Figs 34a, d). The MP1+2 base is reduced either totally or perhaps to an almost indistinct sclerotization above the oblong cell (Fig. A13). Remnants of cross-veins m2 and, especially, m3 are distinct, more or less vein-like, with the m3 base lying within the apical section of RP+MA as the posterobasal border of rc. The distal third of cc is occupied by the base of the apical folding sector, E–X. The cell is certain to have developed such as to be optimal to folding as strictly localizing the field B. This has chiefly been performed by drawing the cc borders close to the folds of the field, with the apical folding sector being stepwise extruded beyond the cell (Fig. 34c). Changes in the cc groundplan were the least in Trachypachidae, Carabidae and some dytiscoids (Dytiscidae: Dytiscinae; Hygrobiidae), being mainly restricted to the m2 and m3 cross-veins transformed into sclerotizations. The border between cc and 1r (RP+MA basal section) under the direct influence of the field B became distally desclerotized in many cases. At the same time, the proximal section of the latter vein curved to the front in many higher carabids and Rhysodidae (Figs A: 12, 15, 18) to localize the field B anterior corner and probably also the field Ka. Rhysodidae and most of Hydradephaga became still more advanced in cc structure. In these, cc became hexagonal through its anterodistal border being unbent (Figs A: 2, 4–6, 12), with the cross-vein m3 pressed distal to rc or reduced completely. This pattern seems to have resulted from parallel developments at least in some dytiscoids, Gyrinidae and Rhysodidae. Apical branches of RP and M. Two branches, RP1+2 and MP3+4, have only persisted along with rms. The latter vein is rarely well-developed, being especially strong and long in Gyrinidae and Dytiscidae (Dytiscinae), but short or rudimentary in most of the other adephages. A strongly elongated rms (Cicindelitae) appears to be a derived character. The vein RP1+2 is seldom straight or almost so. Usually it is more (Figs A: 1–4, 14, 15, 18–20, 25) or less arcuated forward at its base, the origin of this arc suggesting two different explanations. The first implies that the arc could have resulted from a forward shift of the junction of the folds e0 and la while the second invites the arc might have contributed to area Q reinforced during folding. The cubitus anterior, CuA, or the cubital bar, is very strong. Proximal to cp, it is either straight or slightly arcuated backward when combined with the entire

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field A (Figs A: 2, 3, 5–7, 9–13), or slightly convex when the field is subdivided into a few, mostly three daughter fields (Figs A: 1, 8, 14–27). The base of CuA2 persists as a distinct, truncated vein only in some Hydradephaga (Figs A: 2, 6, 9–11). In the remaining Adephaga, it is reduced to an almost indistinct remnant or even completely (Trachypachidae, some Dytiscidae, Gyrinidae and numerous Carabidae). Rhysodidae alone show an entire “cubital spur” (Fig. A12)1. This, however, cannot be reliably homologized with CuA2 since CuA1 is absent; hence, it could be considered as either of these veins or both fused. The vein CuA1 seems to be originally strongly curved just distal to the oblong cell (Figs A5–7). A more or less acute angle between CuA1 and CuA2 appears to be a plesiomorhy as well, the former pattern occurring in Haliplidae, Noteridae, Hygrobiidae (Figs A: 4, 5, 7), Spanglerogyrus (Kukalová-Peck & Lawrence, 1993, fig. 15), as well as Carabidae with a rather large oblong cell which is not attenuating caudad (e. g. Opisthiini, some Nebriini). Trachypachidae (Fig. A13) are likely to be referred to this group as well. The cubital joint (cuj) lies just proximal to the oblong cell (most of Adephaga; also Archostemata). When more proximal (Figs A1–4), it is combined with a geniculate CuA (apomorphy). The free apical sections of CuA1 and of MP3+4 (Myxophaga, dytiscoids) can merge into a common base (Ytu, Torridincolidae: Kukalová-Peck & Lawrence, 1993, fig. 23; Hydroporinae, Dytiscidae, Fig. A11). Small-sized Adephaga show a tendency towards the CuA1 base being reduced either throughout (some Carabidae) or, more often, where intersected by the fold hw (Figs A: 9, 23). The oblong cell strongly varies both in shape and size. It remains rather large and wide in the Myxophaga and Adephaga, except for Rhysodidae and numerous Carabidae in which the cell is completely or partly reduced. In the groundplan, the cell is pentagonal, not or only slightly wider than long (Fig. A2), with a comparatively long cross-vein m–cu4 (Figs A: 2, 5–7, most of Carabidae2); as the posterior border of the cell, the CuA1 base is (more) lengthwise (Figs A: 4, 5, 7, 13) while the transverse axis of the cell is at an acute to right angle to the wing costal margin. The oblong cell starts reducing since it becomes wedgy (Figs 54b; A15). When persisting in approaching each other, the CuA1 base and m–cu3 fuse partly (Figs A: 16, 24) to completely (Fig. A19). Further reduction proceeds in two ways. In the first which is followed by most of the carabids, m–cu4 merges into m–cu3. As a result, the cell grows increasingly small and shifts forward 1

2

Similar but certainly derived conditions occur in Cicindelitae (Fig. A21) and (some?) Paussini. In some Carabidae, this vein seems to have been secondarily somewhat elongated.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

until totally reduced (Figs 54d, e; A22). In the second pathway, the cell opens basally. This begins with a desclerotized short caudal section of m–cu3 (some Pheropsophus, Brachinus, Panagaeus, Melaenus, Fig. 54f) and terminates in a totally obliterated vein (Styphlomerus, Cymbionotum, Dyschiriodes, Dyschirius). As a rule, the reduction of the oblong cell correlates with the body growing smaller

b

a

f

c

g

e

Figure 54. Evolution of the oblong cell in Carabidae; a–g, successive stages.

d

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which can also lead to a different shape of the cell. In, e.g., some Clivinini or Trechini, the cross-vein m–cu3 becomes strongly arcuated backwards, with the caudal section parallel to CuA (Fig. 54g). As the oblong cell transforms, the area W supported by the cell is stepwise modified from irregularly tetragonal (Figs A: 13, 16–18) to triangular. This appears to optimize the folding pattern, which thus seems to be the most probable cause for the above changes to take place. Apical veinal branches (CuP and the anals) in the clavus do not exceed four in number. Conventionally, the vein AA3a' of the beetle groundplan is here considered reduced. This apotypic pattern is also attributed to the Myxophaga. CuP and the 1st anal vein are originally situated on the opposite sides of the claval furrow, the latter being the boundary line between the remigium and clavus. So they serve as material to build up new transverse braces between these wing regions and thus add to their structural-functional integrity. At the first stage of the consolidation process, CuP and AA1+2 were drawn together basally, cu–a1 having grown shorter in between. Since the CuP section between cu–a1 and cu2 merged into CuA, the primary brace as above was replaced by anarc.c. and a joint sclerotized plate composed of fused bases of M, Cu and AA1+2. Further reductions of the CuP and AA1+2 bases brought CuA and AA3 basally into close contact with each other. The CuP primary base was obliterated, but a few Adephaga have retained it either well-developed (Graphoderus, Acilius, Dytiscinae) or rudimentary (Porrorhynchus, Gyrinidae; some Dytiscinae; certain Carabidae: Calosoma, Carabus). The CuP secondary base has persisted distinct or rudimentary only in some carabids (Figs A: 14, 19, 20), declining to a hardly traceable tracheal stem in the remainder. Distal to cu2, CuP is free in Rhysodidae and some Carabidae (Carabini, Siagonini, Nebriini, Opisthiini, Apotomini, Pseudomorphinae, Figs A: 12, 19, 20, 23, 24). In the other adephages, extinct Coptoclavidae included, and myxophages, the apical sections of CuP and AA1+2 shared a common base, cu– a2 having merged into the fusion zone between CuP and AA1+2 (apomorphy). The secondary base of AA1+2 takes off from 1a (Gyrinidae) or 2a (the other Adephaga). A free apical section of the vein is reduced in miniature beetles (Myxophaga, some Hydroporinae, e.g. Hydroglyphus, and Carabidae). The anal cells, 1a and 2a. 1a is much longer than 2a in most of the Adephaga. This implies that it is this pattern that is to be considered as the groundplan for the group in question. 2a varies both in shape and size. Usually it is larger in big-sized beetles (some Dytiscidae, Coptoclavidae), but smaller or reduced in medium- to small-sized ones. Of the veins the 2a is enclosed with, AA1+2+AA3a and AA3b are subequally long while AA3a" is slightly to considerably longer than AA1+2+AA3a. This groundplan is characteristic of most groups (Noteridae; Amphizoidae; most of Dytiscidae; Trachypachus, Trachypachidae; some Carabi-

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

dae: Pelophilini, Carabini, Cicindelini, Hiletini, Omophronini) and tends to be strongly reduced along three pathways, as follows (Fig. 55). (1) The cell gradually decreases in size, culminating in fused anterior and posterior cell borders; this is observed in Gyrinidae1 and hydroporine dytiscids. (2) The cell’s internal (AA3b) and external (AA3a") borders are drawn together and then fused (Figs 55d, g) in Trachypachidae (Systolosoma) and some Carabidae (Siagonini and Paussitae). (3) In most of the Carabidae (Harpalinae s.l., Broscini, Scarititae, etc.), the posterior cell border fuses with subequally long anterior (AA1+2+AA3a) and external (AA3a") borders of the cell. A succession of transitional patterns takes place in this case. Briefly, as the vein AA3b gradually shortens, a constriction between 1a and 2a gets increasingly prominent, with 2a approaching a narrow isosceles triangle. A totally reduced 2a is preceded by AA3b merged into a short stalk that separates 1a from a very narrow 2a (Figs 55, c, f, h ). Following 2a, 1a becomes involved in the reduction process. As veins AA1+2+AA3 and AA4+AP1+2 merge basad, the cell grows shorter from the apex until obsolete (some Myxophaga; Rhysodidae, Fig. A12). This pattern follows a few patterns (Figs 55e; A: 4, 23, 24, 27) similar in appearance, but developed in parallel and perhaps in different ways. This holds true for Haliplidae, numerous Carabidae and some Dytiscidae (Hydroporinae: Hydroglyphus). Venation of the jugum is of unique and highly stable structural plan varying in details only. Primitively, there are two anal veins, AP3 and AP4, in the clavus, of which the former forks. The anterior branch of AP3, AP3a, enters the clavus at the very wing base and merges medially with the vein in front. The posterior branch of AP3, AP3b, lies behind and close to the jugal fold, being always truncated apically. AP4 is unbranched, long, broadly arcuated forward (superficially distad) throughout its length and shortly arcuated backwards at its base. More or less distinct traces of a forked AP4 which occur in Trachypachidae and some Carabidae are considered as a derived pattern, resulting from an unbranched AP4 and the axial cord interacting (Fedorenko, 2006). The cord is well-developed in the groundplan (Gyrinidae, some Carabidae and Dytiscidae) but shows a tendency towards reduction either through dissolution (Figs A: 4, 5, 12, 17, 24) or increasingly shortening from the apex, with the AP4 apex being drawn in the wake (Figs A: 14–16, 19–22, 25). The jugal sclerotization (js) tends to be longer in some hydradephages. As a narrow strip contiguous or close to the axial cord, js extends as far as the AP4 1

In gyrinids, this change could have preceded by partial fusion of the internal, anterior and external borders of 2a with one another. In the course of this transformation, the AA1+2 base might have shifted from 2a onto 1a, with the 2a external border substituting for the anterior cell border.

HIND WING STRUCTURE AND EVOLUTION IN PARTICULAR BEETLE GROUPS

c a

b

f d e

g h

Figure 55. Evolution of the anal cells in the Adephaga; a–h, successive stages.

151

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

apex. It is still rather short in Hygrobiidae, but ranges between occupying the basal third of the posterobasal wing margin and reaching the AP4 apex in most Dytiscidae. When short in many hydroporines, js is likely to be secondary. The folding pattern is of primitive, adephagan type. One of the main features of Adephaga (+ Myxophaga) is CuA2 intersected by the fold hw about midway (synapomorphy). The second is that the anterior corner of field B lies proximal to its outer corner, suggesting this pattern to be closer to the wing groundplan of Coleoptera than to that of Cupedidae (Figs A: 28, 29). The third character concerns the position of fold la. In Archostemata, la is feebly subdivided into a shorter basal section, which is homologous to the fold cq, and a longer distal section conformable to la proper. In the Adephaga, the cq and la sections are either separated distal to the rms apex or meet at an acute angle (apomorphy). Fields A and B either share only one corner (Haliplidae, Noteridae, Amphizoidae, some Dytiscidae; Trachypachidae, Rhysodidae, Gyrinidae: Orectochilus, Gyrinus) or overlap (Carabidae, some Dytiscidae and Gyrinidae: Dineutus, Porrorhynchus), the latter condition probably being derived. The apical folding is more or less spiral or, if flat, then with traces of an apical roll; the more prominent the apical roll, the longer the apical membrane. A more conspicuous apical roll occurs in Gyrinus, Haliplidae, Noteridae and some, mostly small-sized Dytiscidae such as, e.g., Hyphydrus or Laccophilus, i.e. the adephages which show a tendency towards a longer apical membrane. This implies the character involved could be derived and homoplastic in not only the above adephages, but also all of the Adephaga and Archostemata. Adephaga folding their wings flat are more or less naturally divisible into the following groups: (1) Some Gyrinidae (Orectochilus, Dineutus, Porrorhynchus), Amphizoidae, Hygrobiidae and larger Dytiscidae: The apical sector (E–X) is feebly differentiated, with folds varying both in number and position. There is a rather small wrinkled area distal to the rms apex, as well as an incomplete field Sa. In Hygrobiidae, the wing apex is nearly rolled. (2) Trachypachidae + Carabidae are distinctive in having a unique and highly stable folding pattern (Figs A13–27) which is largely characterized by the presence of well-developed, triangular fields Ca and Sa (autapomorphy). This pattern is very likely to have derived from the above, not otherwise. (3) The Rhysodidae folds the wing apex flat, but very irregularly, with the folding pattern strongly varying individually, including in one wing pair. The jugal fold (jf ). The nearly transverse orientation of jf and a rather wide wing base combined result in an evolutionary tendency towards the fold shifting forward, with the modified veins associated with the fold. Accordingly, a folded wing grows narrower following these modifications, among them: (1) Ad-

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ditional folds appear starting from the middle part of jf, including puckerings between AAP and AP3a (Figs A: 1, 3, 6, 7, 9, 10, 19–21, 24). The apical section of AAP first becomes (2) somewhat desclerotized where intersected by some of these folds (Fig. A10) and then (3) reduced (Fig. A9); this sometimes leads to a differently directed AAP and both very narrow 1a and 2a (Fig. A1). (4) A new jugal fold develops. It is composed of the jf base extended into the anterior (superficially distal) of the newly formed folds while all of the folds get reduced caudal to the new jf. Vein AP3a undergoes reduction through this phase as well, with its distal section first disappearing through being cut off by the joined jf (Spanglerogyrus: Kukalová-Peck & Lawrence, 1993, fig. 15) and then a short veinal base obliterated following a broadened 2a (Fig. A2). Some of the above venational modifications, especially the truncated AAP, are certain to have been developed in parallel in Dytiscidae and Gyrinidae. This probably also holds true for some gyrinids. If otherwise, the combination of surely derived characters (a long AAP together with AP3a crossed by the joined jf and partially or completely reduced) argues in favour of the close affinity between Orectochilus and Spanglerogyrus. The sub-cubital binding patch (sbp) is situated caudal to and closely associated with CuP in Trachypachus, Trachypachidae, and all dytiscoids, except for Hygrobiidae and some Hydroporinae (Hyphydrus, Hydrovatus, Hydroglyphus, etc.). The Rhysodidae, the Carabidae, the Haliplidae, the Gyrinidae, the Myxophaga and Systolosoma, Trachypachidae, lack sbp. The occurrence of an analogous patch between CuA1 and CuP in Spanglerogyrus suggests no sbp in ancestral Adephaga. The wing groundplan to be reconstructed seems to be as follows: Articular region. 1Ax with a long posterobasal process, 2Ax with a normally developed arm (BR), 3Ax small; dmp and pmp entire; BM, BCu, med and cub well-developed, but not separate, cub as an anterior process of 3Ax. BR separated from BM by a rounded membranous window. Wing venation. Costal bar spring-like, densely and transversely corrugated throughout its dorsal surface, composed of a very wide ScP and a narrower R– RA, with a distinct border in between. RA partly desclerotized between RP and r1; C+ScA weak to indistinct; both cw and scw well-developed and large; scw much longer than cw. The ScA distal section and the very base of the humeral vein (h) conspicuous. RA reaching the wing tip or almost so, its apex situated distal to fold e0. RP long, nearly longitudinal. Proximal section of M vein-like, shifted underneath R and merged in its proximalmost section; arc distinct but short. The MA basal section vein-like (Gyrinidae, Dytiscidae); rms long (Gyrinidae, Dytiscidae). CuA strong, with CuA2 reduced down its midway (Gyrinidae). CuP free throughout its length, but merged into CuA between anarc.c. and cu2. AA1+2 reduced basally, merged into AA3–AA3a medially, free only distal to

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2a and probably also within anarc. Among three branches of AA3+4, AP3 welldeveloped, the AP3a base bridging AP3b and AP1+2, both AP3b and AP4 long, AP3b reaching level to the secondary base of AP3a (Gyrinidae). Axial cord conspicuous and long, extending up to or beyond AP4. Of cross-veins, m2 distinct, m3 weak (Gyrinidae, Dytiscidae), m–cu2 absent or perhaps fused with m–cu3 anteriorly, cu2 and cu–a2 distinct (Rhysodidae + Carabidae), cu3 wanting, cu1 merged in the fusion zone between CuA and CuP. “Cross-veins” between (superficially) the 1st and 2nd anals formed by the bases of AA3+4 branches which successively enclose a long and wide 1a, as well as a much shorter 2a: AA4 rudimentary, like a small, triangular sclerite at the very wing base; both AA3b and AA3a" long, more or less lengthwise and slightly diverging. Radial cell longer than wide, with its longitudinal axis directed posterodistad; carpal cell of irregular shape, polygonal (Dytiscidae, Carabidae, Trachypachidae); as the border between 1r and cc, the RP+MA basal section uninterrupted and subparallel to cb; oblong cell large, m–cu3 perpendicular to MP–MP3+4 and CuA. The folding apparatus is defined by the combination of a reinforced cbz/cpp and cuj/cp. During folding, cb bends smoothly and twists within 1r; rf is only developed near r1. Fields A and, especially, B large, the latter crossing twice both RP+MA and MP–MP3+4, with the distal corner lying much proximal to the rms base; G moderately large, its distal corner distant from the wing margin, F rudimentary, N reduced, transformed into cf1, H large; fold hw intersects CuA2 at its middle. The apical sector (E–X) lacking closed fields. Cubital joint lying just proximal to the oblong cell. Apical roll flat rather than regular. A sub-cubital binding patch unlikely. In this groundplan, the characters and patterns prevail which seem to be plesiotypic to the Coleoptera, among them a rather primitive folding pattern, a well-developed pst, an apically non-shortened RA, the simple but shortened arc (mp–cua), a conspicuous base of MA, an almost entirely free CuP with its conspicuous primary base; a vein-like RP1+2 (or perhaps RP2); cross-veins m1, m2, m3, cu–a2 and probably also cu–a1 present; both rms and AP3b long; the presence of a AP3a base, a long axial cord and the oblong cell, as well as the shape of the latter cell. This character set can be supplemented by another probable plesiomorphy, namely, dmp sharply subdivided, almost split into BM, BCu and BAA1+2. (Syn) apomorphies are few: a particular structure of cb, with a wide ScP being its body, only three branches of AA3+4 present, no cu3, and the fold hw intersecting CuA2. The myxophagan wing type, especially its groundplan, fit in well with the above. The lack both of primary and secondary bases of CuP, as well as of anarc.c., seems to be derived characters resulting from a very small body size of Myxophaga. The other distinctions are also apotypic and reductionist, which is sure to be due to the same reason. In contrast, differences between the wing groundplans

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of Adephaga and Archostemata + Polyphaga are much more prominent. The absence of the basal section of MA, a differently formed secondary base of CuP and an almost reduced pst combined with an apically strongly shortened RA seem to be the main synapomorphies of the latter two groups. To conclude, the high uniformity of the Adephaga in wing structure is to be emphasized once again. The transformations of the adephagan wing groundplan through evolution seem to have been not so considerable. They culminated in no fundamentally different wing, folding or venation type, being rather individual modifications. Moreover, many of them have been developed in parallel in various Adephaga and Myxophaga. General tendencies in venational changes were chiefly those towards reduction of certain veins. They were also revealed in Polyphaga. Some of them are likely to have stemmed from improved flight functions while the others from folding ones. All veinal reductions appear to merely have lightened the wing. A decrease in body size intensified the reduction process because the elastic properties of the wing membrane compensated for the supporting function of the veins under reduction. Further steps along the pathway of miniaturization led the jugum and clavus to become totally reduced or supported with a single complex vein, respectively. Partly fused CuP and AA1+2 is an example of the consolidation of the clavus’ support through replacing unstable elements such as, e.g., cu–a2, a longer and, consequently, weaker primary transverse brace, with a durable secondary brace, CuP+AA1+2. A desclerotized primary base of CuP is likely to have been the final stage of the consolidation process at the wing base. The vein was apparently lost as not only redundant for the wing support but hampering useful flight deformations after the development of new strong braces such as dmp and anarc.c. between the remigium and clavus. The following modifications can be referred to as sequels to an improved folding apparatus: both rms and oblong cell reduced, changed orientations or reduction of the veins m2, m3 and RP+MA involved in the carpal cell, as well as a modified shape of the latter cell. A truncated AAP and a reduced AP3a are certain to have resulted from change in wing folding. Myxophaga 1 Wing very broad, with a marginal fringe of long hairs, a very narrow clavus and a very strongly to completely reduced jugal lobe. Venation. CuA geniculate 1

This heading is almost exclusively based on the wings as depicted by Kukalová-Peck & Lawrence (1993, figs 25-29).

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at cuj lying much proximal to oblong cell, latter large, as long as, or longer than, wide; cubital spur rather short, but distinct and vein-like. Carpal cell very large, poly- or heptagonal, with strongly desclerotized anterior (RP+MA) and posterior (MP) borders and a straight, transverse and very long internal border; rml much broader than mcl. Clavus basally supported with 1a (Lepiceridae) or at least AA3 extended into AAP. A characteristic Y-shaped pattern present ending in CuP apically while forking into a very short cu2–CuP and the secondary base of AA1+2 antero- and posterobasally, respectively; anarc or anarc.c. lacking. Folding pattern hardly different from that of Hydradephaga, especially Haliplidae: field A strongly to completely reduced, B hypertrophied, its posterior corner lying level to anterior corner and adjoining or approaching cuj, G large and supported with a hypertrophied pcs, latter triangular in shape and extended from cuj to CuA2 apex. The pterostigma is surely pst.c. extended basad to the rc internal border (r1), strongly sclerotized proximal and usually desclerotized distal to the transverse fold e0, of highly characteristic shape, being long to very long, with a posterodistad oblique r1 and a lengthwise posterior border on both hands of “r–m”. The proximal component of the posterior border of pst.c. is either homologous to the middle section of RP+MA or, more likely, secondary, same as in Fig. A23. Myxophaga resemble Hydradephaga, especially Haliplidae, very closely in wing shape and structure. In particular, Haliplidae show (1) cuj rather far distant from the oblong cell, (2) CuA geniculate at cuj while (3 and 4) both r1 and the cc internal border almost transverse, this depending on (5) a particular shape and orientation of field B. The similarity between Myxophaga and Gyrinidae is barely weaker: the latter three interrelated characters are not so prominent in Gyrinidae as in Haliplidae, whereas the former two, in contrast, are sharper and emphasized by a distinct cubital spur (CuA2). But then, as tentatively open caudally, the radial cell is uncharacteristic of Hydradephaga while occurring in small-sized Carabidae. The following two trends in the evolution of the myxophagan wing are noteworthy: (1) towards a completely reduced field A through being superseded by a hypertrophied field B in the course of earlier evolution, and (2) towards a forward or backward shifted base of CuA1. In the former case, CuA1 shifts onto MP3+4 following their bases fused distal to the oblong cell (Ytu, Torridincolidae, and probably also Hydroscaphidae and Sphaeriusidae). In the latter case, the CuA1 base merges first into the external border of the oblong cell and then into CuA2, thus being transformed into a complex cubital spur (Lepiceridae and some Torridincolidae). This modification is also noteworthy to occur in certain Carabidae and probably also Rhysodidae.

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Scirtoidea (Figs A31–35) The wing is wide, with a moderately large jugal lobe separated from the clavus by a deep jugal incision. The groundplan reconstructed below comprises as many venational and folding plesiomorphies as no other polyphagan wing does. Articular region: 1Ax of normal structure, with posterodistal and posterobasal processes subequally long, 2Ax with a normally developed arm, 3Ax small; BM, BCu, med and cub weakly sclerotized. Venation of nearly caraboid type, i.e. full, except for the internal border (m–cu3)1 of the oblong cell and cu–a2 lacking. C+ScA strong, almost reaching rc, free nearly throughout, therefore cw long and wide, with its apex lying much distal to that of a large scw; rc short and wide, tetra- or pentagonal, its internal border formed by a very short r1 extended caudally into the RP+MA distal section. There are m3, a rudimentary rms and the m2, as well as the cc anterior (RP+MA base) and internal (m1) borders; mcl closed due to entire MP–MP3+4; anarc and cuj (Eucinetus) conspicuous, ac and AP3–AP3b long; cu2 long and separated from CuP. Anal cells two (Eucinetus). Apical veinal branches in the clavus reduced down to four in number due to CuP or, less likely, AA3a' loss. AP4 extended to the wing margin. Apical membrane supported with aas–pcas (rp1–RP2), mas (RMP) and MP3+4, the latter conspicuously adjoining “r–m” which is arcuated apicad and situated level, or even distal, to mcl. Sclerotizations of the apical membrane well-developed, including abs, cs and ams. Folding pattern of scirtoid type: fields A, C, S, D, F and G large, K and N persisting as yet traceable, D widely open along wing costal margin, B divided into fields Ba, Bi and Be (synapomorhy). Wing apex folding flat. The combination cpp/cj + ah + cp/cuj is characteristic. This groundplan integrates the folding pattern largely characteristic of Polyphaga and the wing venation distinguishable from that of the coleopteran groundplan by a few apomorphies, among them both cu–a2 and the CuP distal part missing, as well as the veins in the clavus reduced in number. All these distinctions, especially the combination of well-developed m3 and the RP+MA base (in other words, no “Rr” formed yet) argue in favour of scirtoids’ archaism. Further modifications of the above groundplan are chiefly reductionist. The remigium’s basal part becomes relieved from veins through desclerotized borders between 1r, cc and mcl. Namely, veins RP, m1–MA and the RP+MA base get reduced while mcl is modified into a short mediocubital hook (mch) resulting from MP–MP3+4 obliteration (Fig. A34). In the clavus, cu2 and 2a disappear while 1a decreases in size down to narrow and short while ac, sometimes together with the venation of the jugum (Eucinetus), undergoes reduction as well. 1

It is this vein that seems to have persisted in the wing of Calyptomerus.

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Apical veinal branches in the clavus are reduced down to three in number. This results from AA3a' and AAP fused apically following AA3a' shifted onto AA1+2, and the bases of the apical branches of AA1+2+AA3a' and AA1+2 lost. The folding pattern is considerably transformed. In scirtoids proper, Scirtidae and Decliniidae, field A (and, consequently, cp) disappears, delegating the function of longitudinal folding to an extended complex field lying between CuA and AA1+2. This field is largely composed of a tumid field G pieced with the remnants of field N basally and a group of secondary folds posterodistally. Following fields Ba and Bi merged, field Be disappears along with field K and cuj. Eucinetidae. Venation: MP3+4 reduced throughout except basally where fused with the base of a vein-like RMP, with mp2 involved in the fusion zone and thence reduced. Medial bar (MP–MP3+4) reduced in its apical half; 1r, cc and rml merged. A transverse sclerotized patch between fields Bi and Be is likely to be an m2 remnant. There are 1a, 2a and anarc in the clavus; apical branches four, cu2 transverse, AP3a remote from jf, neither ac nor distinct veins in the jugal lobe. Apical membrane without distinct ams, cs, abs and aas. Folding pattern as in the groundplan. Scirtidae + Decliniidae. The character transgression is considerable. The main distinctions are as follows: sclerotization pattern of the apical membrane almost invariable because ams, cs, abs and aas–pcas present while mas (=RMP) reduced completely or almost so; cu2 directed posterobasad or absent, 2a reduced, AP3a running very close to jf. AA1+2+AA3a' takes off from within 1a, implying that 2a has been reduced through the AA3a" base either desclerotized or fused with AA3b. Venation of jugum full: AP3–AP3b conspicuous, AP4 entire or long, ac mostly well-developed. Folding pattern peculiar: fields of B-group reduced to 1–2 in number, G hypertrophied, A and K totally reduced, N and F at least partly so. A secondary, reinforced cubz substituted for cuj. The Decliniidae differs from the Scirtidae by a less derived venation, especially in entire, non-desclerotized medial bar, AA1+2+AA3a' and the AA1+2 base, as well as a conspicuous cu2. However, some characters are surely apotypic, ac, as well as borders between 1r, cc and rml lacking, both mas and MP3+4 very weak, and a distally somewhat shortened AP4 being among them. The folding pattern composed of field Bi and a derived field G also seems to be apotypic (however, the presence of the field Be is not improbable because only one and, moreover, unfolded wing has been studied). A totally desclerotized secondary base of AA1+2+AA3a' is a synapomorphy of Scirtidae. This character could have emerged from two different groundplans. The first occurs in Decliniidae, being characterized by a free base of the AA1+2 apical section. The second, derived, is defined by AA3a' shifted onto CuP–AA1+2. Either way, vein AA3a' (or AA1+2–AA3a') then was fused with AAP apically in all of the scirtids studied but Cyphon retaining this vein free.

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Clambidae. The central region of the wing is occupied by a very large, complex, triangular field. Its anterior, posterior and distal corners adjoin cj, cuj and the back wing margin at the CuA2 apex, respectively. The internal fold of the field is bepr– probably extended into fold bad anteriorly. The posterior and distal folds are gw+ and bq+, respectively, the latter fold extended into a very short fold cw and, then, hw. Hence, this field is a novelty which has emerged from the inclusion of area W into field Be, with fold bep reduced1 while cuj persisted. A strongly to completely reduced jugum and, consequently, its venation are apparently due to a very small body. The folding pattern is certainly derived as compared to that of the other scirtoids, whereas a well-developed cuj and the oblong cell are beetle protofeatures. Staphyliniformia s.l. (Figs A36–69) The wing groundplan of Staphyliniformia = Haplogastra (Kolbe, 1908) = hydrophiloid lineage (Kukalová-Peck & Lawrence, 1993) is only poorly different from that of the cantharoid wing type. All sclerites of the articular region well-developed, including med and cub separated from each other by a membrane zone. Venation: rc of normal structure, pentagonal (Hydrophiloidea); “Rr” long (Hydrophilidae); 1a and 2a large, wide and long. Sclerotizations of apical membrane poorly developed. Folding pattern: fields S and D more or less subequally large, B large but weak, probably secondary, almost lengthwise; D closed and thence cpd developed. As a remnant of the jugal lobe, a well-developed winglet persisting in the elytron (Hydrophilidae). Apomorphies are as follows: the clavus’ apical veinal branches are reduced down to four in number (CuP reduced?); rms, ac and anarc are lacking; r1 is weakened anteriorly, being affected by the field B apex. Yet the main apotypic features are cas and cpd modified into a large pstII and a strengthened apical joint (aj), respectively, as well as CuA2 intersected basally by fold hw. It is the latter two characters combined that determined the general trend in the evolution of the staphyliniform wing. The apical joint is a complex structure largely formed through the wing costal margin being stiffened, thickened and sclerotized around and, especially, on both hands of cpd. In particular, it is strengthened proximal and distal to cpd by the cb apex or a rather short, but wide costo-apical sclerotization (cas), respectively (Figs A: 36, 38). The joint’s axis of rotation is (sub)perpendicular 1

An early reduction of fold bep could account for why the internal border (m–cu3) of the oblong cell and thence the cell proper have persisted in Calyptomerus.

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to the wing plane. This derived pattern (some Hydrophilidae s.l., “Histeroidea”, Scarabaeoidea) develops through a series of transitions. It starts since the wing costal margin at cpd gets first reflexed and then recurved as a small, narrow, but fairly long membranous lobe, thus becoming U-shaped in cross-section. This gutter flattening into a bilaminar structure, with its walls fused, terminates the process. As the groundplan pattern, the gutter has only persisted in Staphylinidae s.l. and Silphidae, with its not too far advanced derivatives occurring in some Hydrophilidae as well. Although there are no fundamental differences between the staphyliniform and “cantharoid” wing types, considerable difficulties arise in homologizing certain veins (or respective sclerotizations), especially RMP, MP3+4, CuA1 and CuA2, between not only Staphyliniformia and other Polyphaga, but also between representatives of different staphyliniform superfamilies. This is largely due to the hydrophilid wing being already far advanced in the venation of the apical membrane while the closest to the groundplan of the staphyliniform wing in general. Nonetheless, the sclerotization pattern of the apical membrane is rather constant (Figs A: 36, 37, 39), albeit not always conspicuous. Usually, abs and aas are distinct while pcas is less so. A strong, lengthwise, vein-like structure which is also often shortened apically occupies the central region of the apical membrane. It is developed from one or, more often, two sclerotized strips, the anterior of them identifiable as cs–mas or the mas base. It is here designated as the vein RMP, with the reservation that it might be of secondary nature (SV). Between RMP and CuA2, veins MP3+4 and CuA1 lie widely separated at their bases, but fused distally (Fig. A37). The staphyliniform wing mainly evolved towards fan-folding, with the following modifications having contributed to this: (1) a modified groundplan folding pattern, (2) a strengthened wing axial support, coupled with the longitudinal veins reduced in number in the clavus and jugum, (3) the apical membrane reinforced with secondary “veins” (SVn)1 and (4) reduction of redundant supporting elements. (1) The basic change is lining the fold sd–la up, with making fields D and S congruous. This “simplifies” and accelerates wing folding: the transverse folding component (D–S) follows the longitudinal one along the sd–la line. The costal bar, CuA and AAP start operating as the fingers of a fan in the basal part of the wing while cas (or pstII), together with primary (RMP, MP3+4) and secondary (SV2, or SV2+SV3) veins, plays this role in the apical membrane. 1

The terminology here used reflects the similarity between these “veins” in position, but it does not necessarily mean their strict homology in the wings of various groups, superfamilies in particular.

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(2) Longitudinal veins become more heavily sclerotized and stouter, mostly wider. Some veins (MP3+4, AAP) get straight and also (more) lengthwise. A reinforced support of the leading edge, with cb at its bottom, is a complex adaptation. In the groundplan (Hydrophiloidea), free C+ScA and ScP are strong, especially so in larger beetles, while cb is supplied with an incipient crimping and conspicuously subdivided into two parts, the anterior ((C+ScA)+ScP) and posterior (R–RA) ones. In Hydrophiloidea s.str., as well as Scarabaeoidea with a long cb, R–RA is also differentiated lengthwise. Of its two components, the anterior is composed of an incrassate veinal wall, implying the supporting function acquired, while the posterior, somewhat desclerotized component protects the respective trachea. Such a triple cb then tends to be equipped with a stronger crimping over its anterior part and a stronger fluting similar to that formed by free ScP– and R–RA+ in many insects. The crimping then grows more distinct and regular while the middle part of cb gets still more frontal in dorsal view, with its anterior and posterior parts acquiring a lower or upper position, respectively (Sphaeridium, Hydrophilidae; most of the Scarabaeoidea). The crimping provides cb with additional flexibility while the fluting adds to the rigidity of the leading edge support and strictly fixes the plane of the aj axis. Since the reduction of the apical joint a direct extension of cb into pstII became a special way to reinforce a very short support of the leading edge in the wing which had a very long apical membrane (a number of staphylinoid families). (3) A membrane fluting reinforced with numerous submarginal “veinlets”, or “ghost” branches, is peculiar to the Sphaeritidae, some mostly big-sized Hydrophilidae and numerous if not all Scarabaeoidea. These secondary veins are dense, weak and (sub)perpendicular to the wing margin, anastomosing one another centrad. As they strengthen and oligomerize, they give rise to vein-like strips of the apical membrane, with some of them being incorporated into pstII together with cas. Stronger strips, or secondary veins proper (SV), are capable of increasing to three (Histeridae) or, probably, more in number. Yet either one or two SV lying close and thence operating as a whole occur more often. (4) Many venational elements undergo reduction, among them rc, “Rr”, Mr, “r–m”, CuA2 (Hydrophiloidea s.str., Histeridae), cu–a2, the AA1+2+AA3a' base, AA1+2 and/or AA3a' and the anal cells. The radial cell (rc) is gradually reduced from being completely sclerotized (Figs A: 36–38, 43), with the veins enclosing the cell merged into its membrane (Glaresidae, Ochodaeidae), through partly reduced in size (Synteliidae, Histeridae, most of Scarabaeoidea) to wanting (Staphylinoidea). 2a opens up predominantly caudally (Figs A: 38, 39). This way of reduction also holds true for 1a (Staphylinoidea, numerous Scarabaeoidea; some Histeridae), with the reservation that 2a could have become open anteriorly in Staphylinoidea (Fig.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

A63). Among the clavus’ apical veinal branches, AA3a', AA3b+(AA4+AP1+2) and AP3a appear reduced in different combinations. A totally reduced Mr is especially characteristic of Staphylinoidea. In the articular region, the 2Ax arm (BR) is often desclerotized (some Scarabaeoidea and at least certain Histeridae: Hololepta), same as the cub distal part (some Scarabaeoidea). Hydrophiloidea s.l. (Figs A36–43) Depending on wing structure, Hydrophiloidea sensu Lawrence & Newton (1982, 1995) are clearly subdivided into Hydrophiloidea proper (= Hydrophilidae s.l.) and histeroids. Although both these groups contrast sharply in appearance, transitional forms do exist. The least derived wing structure is that of Hydrophiloidea s.str. It is barely different from the wing groundplan of the Staphyliniformia, these differences largely being a derived aj structure as well some other characters. Venation: 2a large, wide and long, almost reaching wing margin, welldeveloped even in very small beetles (Georissus, etc.); cb with an inceptive crimping and often also a rather widely desclerotized anterior margin; base of AA1+2+AA3a' and secondary base of AA1+2 not shortened, together with AA3a' associated in a Y-shaped pattern. Sclerotizations: ams and cs absent, abs–pcas, aas, mas and prs more or less distinct; pstII lacking or inceptive. Folding pattern of hydrophiloid type: folds sd and la adjoin each other at a distinct, albeit obtuse angle; when present, membrane puckerings confined to apical half of clavus at best. Synapomorphies: “r–m” sublinear and composed of RP3+4+MA alone due to a reduced mp1; therefore, MP3+4 set apart from “r–m”, starting from anterodistal part of mch between “r–m” and CuA2; latter vein strongly attenuated and often desclerotized apically, usually not reaching wing margin. The main evolutionary trends: (1) Migration of the AA1+2 and AA3a' bases towards and onto 2a, with a correspondingly elongated cu2–CuP. This is characteristic of larger (Hydrochara, Hydrophilus) or, less often, smaller (Spercheus, Berosus) beetles. (2) The development of a weak, more or less diffuse js and a strong, vein-like pjs fused to the 3Ax tail (Hydrochara, Hydrophilus). (3) Distension of the base either of AP4 (Hydrophilus) or AP1+2, the latter through its fusion with a strong and long vein AA4 (Synteliidae, Histeridae, Hydrophilidae: Sphaeridium). (4) Reduction of AA3a' which occurs in some, mostly small-sized Hydrophilidae (e.g. Cercyon) and all of the histeroids.

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(5) The development of the “dryopiform” folding pattern (Georissus, Hydrochus, some Berosini, etc.) is certain to have been caused by the body growing smaller and/or shorter. The tops of folds e2 and hx are already directed basad at an early morphogenetic stage the wings of most of Hydrophilidae s.l. fit in with. However, the latter fold usually remains irregular, being crossed by numerous submarginal folds, while cas/pstII prevents the former fold from entering aj to form cpdd. (6) A reinforced support of the apical membrane mainly stems from certain strengthened and turned longitudinal veins or sclerotizations, this being also accompanied by a reduced CuA2. To substitute for such a CuA2, either RMP and MP3+4 grow stronger and longer (Spercheus, Sphaeridiinae, histeroids) or, more rarely, MP3+4 alone becomes such (Hydrochus). Sometimes SV1 gives rise to a more or less long sclerotized strip extending along the costal margin (e.g. Spercheus or Berosus). (7) 2a opens caudally through the cell’s posterior border, AA3b+(AA4+AP1+2), desclerotized apically. This is observed in histeroids and Sphaeridiinae (Figs A: 38, 39; Cercyon, etc.) to precondition further reduction of this vein and/or AP3a. (8) Changes in the shape and size of the jugal lobe correlate with those in body size and/or shape. A partly to completely reduced jugum results from body miniaturization. On the contrary, stouter and larger beetles that presumably have descended from the small-sized ancestors are distinctive in an enlarged jugal lobe, albeit in a special way (Sphaeridiinae, histeroids). In particular, the jugum becomes hypertrophied through the inclusion of the clavus’ posteriormost part (Sphaeritidae), with a new jugal fold (jf ') formed frontal to jf. Under the impact of jf ' the vein AP3a gets reduced (Figs A: 39, 42) while jf survives or disappears. The trends (1) and (2) appear to result from the body growing in size, whereas most of the others from the opposite tendency towards miniaturization, an increasingly long apical membrane being its immediate effect. A special and apparently important evolutionary trend is the development of the histeroid wing (Figs A40–43). Its most derived variants combine fanfolding and a multiple transverse folding of the apical membrane. However, the pattern (Fig. A43) seems close to the groundplan which is feebly different from that of Hydrophilidae s.l. Both are similar in a fairly rich venation and the rc shape. Distinctive features of the histeroid wing are exclusively apomorphies, as follows: “Rr” rudimentary and shifted onto “r–m” (Figs A: 42, 43), both AA3a' and 2a reduced, a much more strongly developed cas, up to transformed into pstII, at least one secondary vein, SV2, present in front of fold la, a lengthwise or almost so mch section between “r–m” and MP3+4, the folding pattern either of the scarabaeoid or a derived, histerid, type, elongated and stiffened RMP and MP3+4, both supplanting CuA2. A slight to very deep incision of the wing margin distal to the jf tip is also a characteristic derived feature. Distal to a new, increased jugal lobe following a new incision developed distal to the former jugal incision,

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a small additional lobe sometimes appears (Histerinae: Hister, Margarinotus; Merohister: Kryzhanovskij & Reichardt 1976, fig. 18). However, except for a missing CuA2, virtually all of the above characters, not separate but combined, occur in Sphaeridiinae (Fig. A39). Moreover, such characters as a narrow wing shape, with a forward (apicad) expanded jugal lobe, jf ' instead of jf, a reduced AP3a and a pointed 1a add to the similarity between the histeroid and sphaeridiine wings (cf. Figs A: 39, 40 and 41). The wing becomes more specialized from Sphaeritidae to Histeridae. In this series, the wing basal part and apical membrane get shorter and longer, respectively, with their supports reinforced. The axillaries, C+ScA, R–RA and CuA become hypertrophied while the cb–rc unit grows increasingly short to more easily manipulate the wing (Fig. 29). Veins RMP, MP3+4, CuP–AA3a', AAP and either AA3b+(AA4+AP1+2) or AP3a, as well as cas and SV2, stiffen more and grow to serve as fan-fingers. Secondary veins (SV) then develop from membrane corrugation to reinforce the apical membrane while cb–rc becomes the R–RA tip. Simultaneously, the braces between the supporting axes of the remigium’s basal part and apical membrane strengthen where apparently facing the heaviest folding deformations: abs–pcas is modified into a narrow bridge between RA and SV2 (Figs 29, A41) while RMP shifts onto MP3+4 (yet this area might have become so consolidated in relation rather to flight than folding). Transverse braces cramping the movability of fan-fingers undergo reduction, these decreasing in number in the clavus. More specifically, the brace (AA1+2+AA3a') between CuP–AA1+2 and AAP disappears. A reduced AP3a (Synteliidae, Histeridae) or AA3b+(AA4+AP1+2) (Sphaeritidae) is followed first by a partly to completely desclerotized base of AA4+AP1+2 (Histeridae) and then by an obliterated vein AA3b+(AA4+AP1+2). In larger beetles, this process terminates in only two fan-fingers retained, since AA4+AP1+2 is either partially desclerotized (Hister, Margarinotus) or strongly shortened (Hololepta). These modifications seem to largely stem from shortening both the elytra and hind body. Miniaturization that accompanies or follows these changes results in a still shorter basal part of the wing, as well as in many of the primary and secondary veins weakened or reduced (e.g. Plegaderus: Kryzhanovskij & Reichardt 1976, fig. 21). Scarabaeoidea (Figs A44–62) The wing is of highly characteristic shape and structure, the broadest at about the middle, subequally narrowing both basad and apicad, with a rather small jugal lobe and usually also a wavy posterior margin.

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Venation: rc rudimentary, strongly and evenly sclerotized, with membrane inseparable from surrounding veins; “r–m” poorly visible and pointed apicad in the form of a weakly sclerotized V-shaped strip. Two anterior veins in clavus, CuP–AA1+2 and AA3a', isolated; AA3a' often lacking, rarely (e.g. Valgus, Scarabaeidae) both these veins wanting. Both 2a and cu2 totally reduced. Mr primitively longer than half of CuA. 1a often open distally. Sclerotizations: membrane crimping well-developed, reinforced with numerous “ghost” branches; cas conspicuous, usually as a compact pstII far distant from wing apex; cs–mas and aas rather weak; cas/pstII and a narrow, strongly sclerotized SV2 apparently separate in the groundplan (Fig. A46). The following structures seem to be secondary: abs, the pcas distal and wide basal parts, js, pjs, icsp and costo-apical bridge (cab, Figs A: 47, 50, 55) bracing the pstII and SV2 bases. Articular region: In the groundplan, the 2Ax arm (BR) is well-developed, BCu weakly structured, triangular, separated from Cu by a deep furrow, 3Ax rather narrow. BR shows an obvious tendency towards reduction, BCu becomes transverse and vein-like in its distal part while 3Ax is strongly enlarged. Folding pattern is of scarabaeoid type. Fields C and B overlap. The main evolutionary trends: Consolidation of the leading edge support (1) Modifications in cb structure appear to largely stem from the apical joint improved through stiffening the wing margin on both sides of aj and simultaneously adding to the flexibility of the cb distal part. While already observed in Hydrophilidae, this tendency results in a stronger fluting and a sharper corrugation of at least the anterior part of the triple cb, culminating in a narrowly carinate R–RA in the cb apical part. This character is the most prominent in larger scarabaeids (Scarabaeus, Cetoniinae, etc.) whose costal bar seems to be the most strongly affected by folding and thence invited to consolidation. Deviations from this general line are chiefly confined to cb flattened at least apically, with a partially (Anoplotrupes) to completely (Codocera; Passalidae) reduced corrugation and sometimes also an almost desclerotized posterior part of cb (some Passalidae). These few despecializations might have come out of some fall in flight activity. (2) The reduction of cw is characteristic of a wide range of the Scarabaeoidea: Glaphyridae, Geotrupidae (Anoplotrupes), Ochodaeidae (Codocera), Ceratocanthidae and Scarabaeidae: Cetoniini, Scarabaeinae (e.g. Copris or Sisyphus). Some melolonthines (Polyphylla) and dynastines (Pentodon) also deserve to be included in this group in showing a rudimentary, almost invisible cw. An originally fairly short and narrow cw of Scarabaeoidea seems to have been a precondition for the reduction to take place. This also follows from the opposite tendency towards a larger cw being only rarely observed in the superfamily (Valgus).

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Modifications in the sclerotization pattern of the apical membrane The groundplan combines the following elements: poorly developed cs–mas and aas, cas in the form of a rather short pstII not contiguous to the wing costal margin; a moderately strong membrane crimping, with numerous and subequally weak branches of which only one is transformed into a narrow, vein-like SV2; SV3 undeveloped or much weaker than SV2 at best. This or a very similar pattern is peculiar to Lucanidae, Trogidae, Bolboceratidae and Glaresidae, with the intergroup differences being negligible and restricted to the lack either of SV3 (Glaresidae) or the pcas basal part (Lucanidae, Glaresidae), or cab (Glaresidae, most Lucanidae), or aas (Trogidae). At the next stage, a pattern is developed distinguishable from that of Bolboceratidae (Fig. A47) by a more or less well-developed abs. When represented by the line abs–cs–mas–aas, this pattern is U-shaped (Passalidae, Ochodaeidae, Geotrupidae, some Hybosoridae: Hybosorus). Yet it looks like “S” lying sidelong provided the sclerotized patches proximal to abs are involved in that line (Fig. A56). It is uncertain how these two patterns interrelate morphogenetically, but the former being combined with such obvious plesiomorphies as a more distinct “r–m” and a larger rc suggests the plesiomorphy of the U-shaped sclerotization as a working hypothesis. Based on this, the proximal component of the Sshaped sclerotization is supposed to have resulted from rc growing shorter but more lengthwise, partly because of its posterodistal border unbent. The S-shaped pattern is observed in most of the Scarabaeidae (Melolontinae, Dynastinae, Rutelinae), as well as Glaphyridae (Fig. A53) and some Hybosoridae (Fig. A55). When only cs–abs is retained, the pattern is first transformed into a Г-shaped (Scarabaeinae, Fig. A62) and then a transversely linear one (Aphodiinae, Fig. A61). Because a sublinear pattern of Cerathocanthidae (Fig. A51) is coupled with a large rc, it seems better to be considered derived from the U-shaped pattern. Individual sclerotizations and secondary veins evolve in the following way. In particular, pstII rarely remains short and membranous along the costal wing margin (Serica, Melolonthinae). Usually it grows longer and stronger at least caudally (Codocera, Ochodaeidae; Scarabaeidae: Aphodiinae, Aegialiinae, Scarabaeinae, Hoplia). Still more often, especially in larger beetles, pstII evolves into a strongly sclerotized and vein-like cas supporting the costal margin throughout the apical membrane (Passalidae, Hybosoridae, Geotrupidae, Glaphyridae, numerous Scarabaeidae: Dynastinae, Rutelinae, Melolonthinae, Cetoniinae). SV3 gets reduced or merged in SV2 while cab and aas become strong, thence all these are embodied into a Y-shaped pattern (Passalidae, Hybosoridae, Geotrupidae, Scarabaeidae Laparostici). In the Pleurostici, SV2 is split into two narrow strips, SV2a and SV2b. It is such a treatment that I follow here, with the reservation that the posterior strip

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may be conformable to a strengthened pcas–SV3. Caudal to SV2b, strips SV3 and SV4 can develop, the former running parallel to SV2b (Fig. A62), the latter taking off from the SV2b base towards the postero-apical wing margin (e.g. Scarabaeus). A strip analogous to SV4, combined with a lacking SV2, is a characteristic of Glaphyridae (Fig. A53). Incipient homologues or analogues of this strip occur also in Geotrupidae (Fig. A48).

b

a

c d

e

f

Figure 56. Evolution of wing venation in the clavus of Scarabaeoidea: hypothetic ancestor (a); groundplan of the scarabaeid lineage (b); Lucanidae, Trogidae (c); Passalidae (d); Bolboceratidae (e); advanced Scarabaeidae (f).

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As a narrow strip pointed at the extremities, icsp lies behind and very close to CuA–MP3+4. The strip serves for supporting a narrow field somewhat analogous to G. It is originally very weak to indistinct (Fig. A45), growing much stronger in many Scarabaeoidea (Figs A: 56, 58–61), especially Scarabaeinae (Fig. A62) in which icsp looks like a vein and reaches the MP3+4 tip apically. This pattern is certain to have emerged from a forward shift of a convex fold of the hw group, resulting in the fold intersecting vein CuA–MP3+4 before its apex and constituting the anterodistal border of the field involved, versus formerly running behind the vein. The jugal sclerotization (js) can develop as a narrow and fairly weak strip starting from the AP4 base and then passing more or less close to the posterobasal wing margin (Hybosoridae, Geotrupidae, Scarabaeidae). This strip remains weak or is degenerated in smaller beetles or those showing a strongly reduced jugal lobe (numerous Scarabaeinae, Cetoniinae: Valgus). In larger beetles, js becomes very prominent, transforming into a secondary vein that passes along (Scarabaeinae: Scarabaeus, Copris) or very close to (Scarabaeidae Laparostici) the posterobasal margin of the wing. Sometimes, pjs is added to js. It rims the posterobasal wing margin, fusing with 3Ax at the pjs base (Cetoniini, Fig. 30). A supporting function and a secondary nature both of js and pjs are beyond doubt. Reduction of the clavus venation (1) Reductions of the isolated veins ending in AA1+2 or AA3a' follow change in the veins’ relative position. The following pattern is here recognized as the groundplan (Lucanidae, Trogidae, Bolboceratidae): (1) AA1+2 straight to feebly arcuated forward, with its base either almost equidistant from AAP and CuA or lying a little closer to AAP; (2) AA1+2 and AA3a' either running parallel to AAP or diverging from AAP apically; AA1+2 equidistant between AA3a' and AAP. A derived pattern (Glaresidae, Ochodaeidae) underlies the others observed in Scarabaeoidea. It differs from the above by AA3a' and AA1+2 lying close to AAP or closer to the CuA base, respectively, with AA1+2 distinctly, but very obtusely angulate where its short, lengthwise, basal section extends into a much longer and more transverse apical one. AA1+2 and AA3a' disappear together only occasionally (Fig. A59). Usually, AA3a' is only reduced either totally (Passalinae, Glaphyridae, some Hybosoridae: Phaeochroops; Scarabaeidae) or to a feebly sclerotized strip (some Aphodiinae and Scarabaeinae). When alone, AA1+2 gradually shifts basad, getting increasingly transverse under the influence of the fold hw (numerous Scarabaeidae). It follows that a totally reduced AA1+2 may have resulted either from the immediate intersection by the fold or a more transverse orientation of the vein which could have hampered the longitudinal wing folding between CuA and AAP. (2) Figure 56 shows how veins caudal to AA1+2 could have evolved. Following this scheme, I derive the entire diversity of scarabaeoid venation patterns

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from something close to the pattern observed in sphaeridiine hydrophilids (Fig. A38). The Scarabaeoidea is thus divided into two lineages, depending on which particular vein posterior to AAP has been lost. The posterior vein persisted, AP3a, defines the lucanid lineage. This comprises Lucanidae, Bolboceratidae and Trogidae. The lineage is also distinctive in the basal section of the 1a posterior border (AA4+AP1+2+AP3a) being shorter and more or less directly extended into AP3a, albeit varying in length. Several rudimentary veins of the groundplan pattern are sometimes retained still traceable, among which the very base of AA3b+(AA4+AP1+2), as well as AA3b set perpendicular to AAP (Sinodendron, Lucanidae; Figs A: 45, 46). The remaining Scarabaeoidea seem to have lost AP3a while retaining AA3b+(AA4+AP1+2). They are referred to the scarabaeid lineage. This is defined by the 1a posterior border either angulate (Figs A: 48, 51, 54–55, 61), sometimes with a short remnant of AP3a (Hoplia; Figs A: 53, 56), or very long (Figs A: 50, 57–59, 62). As tentatively placed here, Passalidae and Glaresidae are of special interest. Both are distinctive in showing a very long posterior border of 1a, combined with an extremely short external border of the cell (AA3b, Fig. A49) in the former family or with the jugal fold far distant from 1a in the latter (Fig. A52). (3) A specialization within Scarabaeidae can bring 1a into being strongly decreased either in size (Fig. A60) or width (e.g. Fig. A59) to totally reduced (Sisyphus). 1a also definitely tends to open distally. A quite close cell is very likely to be a derived pattern in all scarabaeoids, except perhaps Bolboceratidae. Reduction of the jugal lobe. The jugum tends to diminish in size in all higher taxa, this tendency being the worst expressed in Lucanidae, Passalidae and some relatively small-sized beetles with longer elytra (Hybosoridae, Aphodiinae). A strongly reduced jugal lobe occurs in Glaphyridae, numerous Scarabaeinae and Trichini, Cetoniinae, whereas a completely reduced jugum is observed in Valgini. The Cetoniini shows the opposite tendency, that towards an enlarged jugum which is uncharacteristic of the Scarabaeoidea in general. Conspicuously enlarged bases of AA4–AP1+2 and AP4 is a distinction of Scarabaeidae and some Hybosoridae (Fig. A55). Less so these veins are in Glaphyridae (Glaphyrus), Hybosoridae (Phaeochroops) and Anoplotrupes. More deeply this trend concerned AA4–AP1+2, supplying its base with a particular shape and structure. With AA4 having merged into the AP1+2 base, this base took the appearance of a convex vein-like structure tapering apicad. A secondary veinlike sclerotization skirts it anteriorly. The middle part of the entire structure is homologous to a totally desclerotized AA4 while its posterior margin conforms to the primary base of AP1+2. Reduction of rc. The largest, namely longest, and angulate cell occurs in Glaresidae (plesiomorphy). However, rc is barely shorter in Trogidae, albeit rounded along its posterodistal margin. The same holds true for a subangulate rc of Codocera,

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Ochodaeidae, with that of Passalidae also approaching it in shape and size. The latter family’s rc lacks a distinct posterior border and may have been enlarged secondarily. In the remaining Scarabaeoidea, rc became strongly shortened through its internal and external borders drawn together, the cell mostly retaining its original shape (the posterodistal margin arcuate) or, more rarely, unbending (Anoplotrupes). The most strongly reduced rc is observed in Scarabaeinae and Aphodiinae. Reduction of the 2Ax arm (BR). This part of 2Ax is totally desclerotized in Glaphyridae, Passalidae, Scarabaeidae and some Lucanidae (e.g. Ceruchus), remaining very thin and nearly piliform in Anoplotrupes. Desclerotization of the costa (superficially the anteroventral wing margin distal to HP). This not too strong tendency is only shown by Scarabaeinae, as well as some other, mostly big-sized Scarabaeidae (e.g. Polyphylla or Pentodon), sometimes resulting in the development of a conspicuous membranous flap (Cetoniini, Cetoniinae; Onthophagus). Improvements of the folding mechanism The wing folding patterns of Scarabaeoidea naturally fall into two groups, lower- and higher-grade. The former comprises nearly all of the Scarabaeoidea, but Scarabaeinae and Aegialiinae–Aphodiinae belong to the latter group. Representatives of the lower-grade group have retained the folding pattern close to the groundplan. Its elements were slightly modified, with only few novelties occurring. Among them, abs and pcas stiffened the wing membrane inside and outside the field D, respectively, so as to strictly localize the folds dq and de. A similar effect resulted from certain neighbouring veins and folds approaching each other. Such couples were the external border of rc/fold dq (Passalidae, Ochodaeidae, Geotrupidae) or the anterodistal border of mch/fold cw. In the latter case, mch broadened apically, the vein having become erect. This tendency appears to have arisen in the course of the early evolution of Scarabaeidae Pleurostici (Fig. A56), with its fruit being a synapomorphy of Dynastinae, Rutelinae, Melolonthinae (Fig. A57), Euchirinae and probably also Cetoniinae s.l.; yet the latter group seems to have almost reverted to the groundplan (Figs A58–60) due to a very narrow basal part of the remigium. Certain Scarabaeoidea, especially Cetoniinae and Glaphyridae, show the caudal part of field B narrow, lengthwise and extended to the wing base, combined with all longitudinal folds oligomerized to principal three, la–, gu–gw+ and gv–. This came out of accessory folds having been reduced between RMP and MP3+4, as well as between MP3+4 and AAP. This folding pattern seems to be an adaptation to speed up wing folding and, especially, unfolding, this obviously being topical for the beetles which flush readily. But Aphodiinae and Scarabaeinae display the most derived folding apparatus. This seems to be so because the strong and regularly fluted branches of

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the membrane crimping supply the wing membrane with great springiness. The membrane puckers which formerly occurred only between RMP and MP3+4 spread all over the wing sectors in veinal forks (Aphodiinae) or over sectors SV2 – RMP and MP3+4 – AAP (Scarabaeinae). The primary folds under the influence of these puckers gradually declined as they lost regularity and polarity. Among them, fold la became the most strongly reduced and thence supplanted with several, new, convex and/or concave folds frontal to it. These folds emerged from secondary longitudinal folds lying either between the strongest branches of the membrane crimping or between those branches and SV2. Thus, the venational groundplan of Scarabaeoidea evolved towards a pattern composed of a few strong longitudinal veins, with few or no elements to brace them. In the course of this alteration, cb became consolidated, including through being more strongly associated with a modified rc. The anal bar (AAP) straightened, with partly to completely reduced anals in front; this might have been caused by the direct influence of folding. The groundplan sclerotization pattern was modified in the apical membrane, both outside and inside fields D and S, as well as in the jugal lobe. In particular, distal to the field D, the wing costal margin was reinforced into kind of a strong “vein”, with a prominent SV2 emerging from the membrane crimping through the early evolution. Within both D and jugal lobe, abs and js were formed, respectively. Staphylinoidea (Figs A63–69) Groundplan features: Wing rather narrow, with a conspicuously elongated apical membrane, cu2 (Staphylinidae, Silphidae), traces of the AP3a base (Silphidae) and probably also ac (Pteroloma, Agyrtidae). Mr short and strongly desclerotized or rudimentary; rc and “r–m” totally reduced (autapomorphy). Anterior two veins in clavus, AA1+2 and AA3a', sharing a common base (CuP+AA1+2+AA3a'), AA3a' at apex lying much closer to AAP than to AA1+2; 1a large but open apically (Figs A: 63, 64), 2a missing1. Apical membrane reinforced with three (SV2+SV3, RMP and MP3+4) or four (+ SV1) subequally developed veins or strips, CuA2 rudimentary, short and desclerotized (Scydmaenidae, Leiodidae, Fig. A64). Costo-apical sclerotization (cas) hypertrophied into a strong pstII (synapomorhy). Field B lacking, C long and very narrow, S and D small and 1

The following ways of reduction could have been executed: (1) fusion of the veins skirting 2a, (2) opening of the cell anterior border, AA1+2+AA3a (or perhaps partly CuP+AA1+2+AA3a), or (3) opening of the cell caudally. Conventionally, I follow the first of the options and accordingly designate the veins.

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probably lengthwise; apical joint (aj) of a very primitive structure, gutter-like. Wing apex fan-folding, including along folds la– and hi–xi+. This groundplan has given rise to two rather different wing types each combining both plesiomorphies and apomorphies. In general, the staphylinid wing type (Staphylinidae s.l., Silphidae) (Figs A66–69) seems to be more primitive, retaining almost groundplan venation and, especially, folding pattern. Apomorphies seem to be only ?MP3+4 substituted for CuA2 and the presence of field Bs. In contrast, the agyrtid wing type (Hydraenidae, Ptiliidae, Agyrtidae, Leiodidae, Figs A: 63, 64) looks more derived. This in full measure holds true for the nominate folding pattern and the venational characters consequent upon its development, among them a totally reduced apical joint resulting in cb extended into, and thus reinforced with, pstII; in addition, this new, consolidated costal axis is somewhat shortened. Plesiomorphies are only restricted to a more or less distinct CuA2 (Fig. 64) if any. The latter character, as well as SV1, also occurs in Scydmaenidae. I am also inclined to refer this family to the agyrtid wing type as fitting in well with, except for a rudimentary apical joint (plesiomorphy). In spite of the considerable structural differences observed, the above two wing types share evolutionary tendencies towards (1) a reduced jugal lobe and (2) the retention of only one strong anal vein ending in AAP or perhaps AAP– AA3a' (Scydmaenidae). (1) A strongly decreased jugal lobe is preceded by the jugal incision growing much deeper. A totally reduced jugal lobe is characteristic of most of the agyrtoids and extremely small-sized staphylinoids (Rybaxis). Many Staphylinidae, on the contrary, retain the former functional size of the jugal lobe, since a hypertrophied marginal fringe compensates the increasingly small jugum for this loss. (2) AA1+2 and AA3a' first become isolated due to the shared base reduced and then gradually shortened from their bases (e.g. Pteroloma, Oxyporus, Philonthus). AA1+2 disappears first (e.g. Scaphidium, Stenus, Bledius) and AA3a' after. Simultaneously, the anterior anal stem (AAP) straightens up while the other anal veins, both transverse (cu2, AA1+2+AA3a') and longitudinal ((AA4+AP1+2+AP3a)–AP3a), get completely reduced. Scydmaenidae, Hydraenidae, numerous Leiodidae (Leiodinae: Colenis, Agathidium, etc.; Sciodrepoides, Cholevinae) and Staphylinidae (Scaphisoma, Rybaxis, etc.) are at the summit of this trend. Such a wing type has apparently resulted from a fairly stout body growing smaller. Further decrease in body size can lead the agyrtid wing to a much more derived, plumose wing of Ptiliidae (Fig. A65). This is defined by neither a clavus nor a jugum, with the wing basal part transformed into a narrow, homogeneous, sclerotized stalk, as well as the presence of a hypertrophied marginal fringe

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compensating the wing for its strongly reduced membrane, and the absence of a longitudinal folding. Some special evolutionary tendencies are to be discussed. (1) An almost completely reduced cb (Silphidae, Staphylinidae but Omaliinae) stems from a strongly shortened basal part of the remigium. Because cb shortens more rapidly than both a free R and ScP do in such a wing, it is these veins that become the major integrants of the leading edge support. The following structural modifications contribute to the consolidation of the axis: R and ScP strengthen and approximate each other, being separated by an extremely narrow scw all along, with R getting superimposed on ScP. A desclerotized C+ScA and the anterior part of cb appear to contribute to this pattern by adding to the movability of ScP relative to the wing costal margin. (2) In some larger beetles (Silphidae; Staphylinus, Staphylinidae), these desclerotizations often evolve into membranous flaps, these being long and wide extensions of the costal margin. An originally shorter flap (Fig. A66) can extend beyond aj as a narrow lobe (Fig. A67) afterwards. (3) The development of the agyrtid folding pattern has resulted in an almost reduced field association C–S–D and cpd. This seems to have made the cb–rc unit preadapted to further extension into a large pstII and thus reinforced. (4) A strongly extended jugal lobe supported both by a reinforced AP3a and, less so, AP4 (Fig. A66) has probably resulted from a rather large and stout body of the Silphidae. (5) Shortening of pstII. In the groundplan, pstII is fairly long, gradually narrowing distad (Silphidae; Omaliinae, Staphylinidae) and somewhat desclerotized distal to the transverse fold e2 it is intersected by. It seems very likely that this weakened distal part of pstII undergoes reduction under the direct influence of the fold, thus leaving the body of pstII truncated in numerous Staphylinidae. (6) Di- or, presumably, polymorphic folding patterns stem from a saltatory change in a pattern of higher complexity, namely, through its simplification resulting from several folds reduced, combined with some others that acquire different orientations (cf. Figs A68 and A69). Sometimes the simplified pattern is as frequent as the normal one, both often occurring in a single wing pair (Oxyporus). A greater part of evolutionary alterations as above have emerged from the apical membrane growing longer. This has largely been due to shortened elytra and/or the body decreased in size. The longer the apical membrane, the shorter the wing’s basal part, and the more complex the folding pattern, this complexity chiefly resulting from the multiplication of transverse folds. A wealth of folds and the direct influence of some of them, especially hw, cause the clavus’ anterior veins to be isolated and then reduced.

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Elateriformia s.str. (Figs A70–106) Wings varying from narrow to very wide, but usually of normal shape, with a long basal part and a short or very short apical membrane and no jugal incision. The main distinctive features are as follows: (1) rms missing, (2) veins or veinlike strips of the apical membrane detached from “r–m” due to a reduced base of MP3+4, (3) venation rich and nearly full (rc large, “Rr” and Mr long, cu2, Cur and cu–a2 usually long as well; apical branches of anal veins six). Venation patterns often vary individually (Elateroidea, Byrrhoidea, Buprestidae). The most frequent aberrations are a doubled r1 (Elateroidea, Buprestidae), 6–7 apical veinal branches in the clavus, and some anal veins distorted and fragmented. The groundplan. Articular region: A convex round field is well-developed between HP and BSc+BR to fit the basalare button ventrally. 1Ax with subequally long posterobasal and posterodistal processes (Elateroidea, Byrrhoidea); 2Ax entire. Pmp–dmp feebly structured: med and cub (sub)contiguous, basally somewhat shifted towards 2Ax and apically extended into BM and BCu, respectively, these fused or subcontiguous. 3Ax enlarged due to its head extended and a secondarily sclerotized membrane incorporated into what is contiguous to the sclerite posterodistally. Venation: rc pentagonal (Figs A: 77, 78), with its outer border (external and posterodistal borders combined) formed by r2–(r2+RP1+2); “Rr” long, bearing remnants of both the RP base and m1 basally (Figs A: 81, 82, 85, 97, 100-102); “r–m” more or less straight and transverse, rms absent; Mr moderately long, but disappearing far from arc.c. (Figs A: 70, 77, 95, 102); CuA strong. Venation of the clavus and jugum conforms to the groundplan of Polyphaga: apical branches six, 1a and 2a large, cu2 moderately long and transverse, cu–a2 long, more or less lengthwise (Elateroidea), Cur long. Apical membrane supported by three longitudinal strips rising from shared but weak base (cs); among them, the medial (RMP) and posterior (MP3+4) look more vein-like than the anterior strip (aas–pcas, or rp1–RP2). Secondary base of MP3+4 (distal to “r–m”) reduced, so MP3+4 adjoining neither “r–m” nor mch, nor CuA2 base. Of the remaining sclerotizations of the apical membrane, abs (Figs A: 77, 78, 81), cas and ams weak to indistinct, abs not sclerite-like. Folding pattern of the “clavicorn” or, more likely, “elaterid” type, with field C not extended basad (Figs A: 70, 100–102), a well-developed A, an open D (Figs A: 70, 71, 73–75, 77, 78, 84, 100–103), and B lying distal to m1 (Fig. A70). Transformations of the groundplan were not profound. They only marginally involved wing venation and more strongly the folding pattern. The main structural modifications in the groundplan are as follows. (1) Modifications in the articular region are primarily observed in pmp–dmp structure, going in two main directions, as follows. A structured sclerite is char-

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acteristic of Elateroidea (Elateridae and “cantharoids”). In particular, med and cub tend to become increasingly separated from each other, with cub divided into two parts; of them, a triangular proximal part is wide basally while a narrow distal one is extended apically into BCu (Fig. 31). Some general forward shift of dmp occurs in Byrrhoidea, Dascilloidea and Buprestidae. In most of the Buprestidae, pmp–bmp is transformed into a narrow, Λ-shaped sclerite. (2) Transformations of rc. Elongation of rc through the extension of its posterobasal (r2+RP1+2) and/or posterior (RP+MA) border is realized in all higher taxa but Dascilloidea. As a result, the former vein is the longest in some Buprestidae (Figs A: 104, 105), Omalisus, some Eucnemidae and, especially, numerous Elateridae (e.g. Figs A: 79, 82–86) while the latter is such in “Cantharoidea” (Figs A: 89, 90; Malthinus), Phyllocerinae (Fig. A72) and some Elateridae (Figs A: 77, 81; Tetralobus, Pityobius, Elatichrosis, etc.). Dryopidae, Limnichidae, Heteroceridae and Elmidae show rc open, resulting from its internal border (r1) desclerotized under the effect of field B anterior corner; this pattern follows r1 obsolete only where adjoining RA (Callirhipidae; some “cantharoids”, e.g. Omalisidae). The cell’s anterior (RA) and outer (r2–(r2+RP1+2)) borders merging basad culminate in a totally reduced rc (Fig. A106). Finally, cross-vein r1 shifting distad leaves rc increasingly small, with the RP+MA section between r1 and “r–m” shortening until missing (Figs A: 97, 101). The veins r1 and (r2+RP1+2)–r2 then merge caudally, leaving “Rr” shifted onto “r–m” (Figs A: 80, 91, 92, 98; Rhinorhipidae). The latter transformation is largely uncharacteristic of Elateriformia, since it usually comes out of body miniaturization, this being well-traced only in some Elateroidea and Byrrhoidea. Hence, when found in a larger beetle, this pattern may point to its origin from smaller ancestors. (3) Changes in Mr length. A shortened Mr (Dascilloidea, Buprestoidea, Rhinorhipidae, Byrrhoidea, some Elateridae) is assignable to different causes, whereas an elongated one (most of the Elateroidea) seems to have been an adaptation to strictly localize the fold cw of a strongly elongated field C. (4) Shift of AA1+2 onto CuP is a steady trend resulting from the reduction of cu–a2. The resultant pattern is developed in parallel in Dascilloidea + Buprestidae, Rhinorhipidae, psephenoids, some dryopoids, Eucnemidae s.l., Cantharidae and many groups of Elateridae s.l., sometimes varying even individually (e.g. Brachypsectra). It appears to have stemmed from or intensified by a decrease in body size at least in some of these cases. (5) Venation of the clavus is simplified through the veins being more or less successively reduced in the following series: Cur (mainly Elateroidea: most of “Cantharoidea”; Cerophytidae, some Eucnemidae, some, especially small-sized, Elateridae: numerous Negastriinae) – the base of the CuP apical section (some

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Dascillidae and Buprestidae, Figs A: 102, 104, 106) – the entire CuP (some Byrrhoidea: Ptilodactylidae, Chelonariidae, Byrrhidae, some Elmidae, Psephenoides, Psephenidae; Trixagus, Throscidae; certain Elateridae: Negastriinae) – the AA1+2 and/or AA3a' bases (Grouvellinus, Elmidae; Psephenoides, Psephenidae) – the entire AA1+2 (Heterocerus, Psephenidae; Chrysobyrrhulus, Byrrhidae, individual variability) – all of the apical branches, except for AAP (Eubria, Psephenidae; Limnichus, Limnichidae; Drilidae) and also AP3a (Syncalypta, Byrrhidae). The Byrrhidae shows an extremely variable pattern frontal to AAP: the veinal branches are often fragmented, distorted and either partly reduced or anastomosing one another. Reduction of free veins can be concurrent with 1a opening through its posterior border strongly desclerotized all along (Limnichus) or only apically. This pattern reaches completion in some Elmidae, being inceptive in Ptilodactylidae. (6) Separation of 1a and 2a results from AA3b growing shorter (some Ptilodactylidae, Elateroidea: Omalisidae, Lycidae, Omethidae, numerous Elateridae). (7) 2a gets reduced chiefly through desclerotization of its external border (AA3a") (Electribius, Artematopodidae; Brachypsectridae; numerous Elateridae, all of the Agrypninae in particular, Figs A79–82; some Eucnemidae: Fig. A74, Otho; Cantaharidae: Rhagonycha, Cantharis; numerous Byrrhoidea). This change is often supplemented by 1a and 2a separated by a more or less long stalk (Figs A: 74–76, 78, 80, 91, 96, 97). When very large, 2a can open postero-apically, thus leaving veins AA3a"–AAP and AA3b+(AA4+AP1+2) relieved at the wing margin (only some Buprestidae: Figs A: 105, 106). (8) Desclerotization of C near HP is observed in larger beetles (Buprestidae, Rhipiceridae). (9) Size alterations of field C. A general evolutionary trend is that towards a basad strongly extended field C. It also leads to a basad shifted field B (more precisely, supplanted with a daughter field, B') and a strongly to completely reduced field A (almost all Elateroidea but Artematopodidae). To a much lesser extent, the tendency manifests itself in some Byrrhoidea (Figs A: 94, 98, 99). A strong fall in the folding function of the C–S–D unit accounts for some of its decline, as well as a shortened field C (Byrrhidae, Psephenidae). The C–S–D functional unit is almost superseded with the R–H unit in Psephenidae. (10) Oligomerization of the central field group (S–Ia–Ip). Either field Ia (Cantharidae, Buprestidae, Dascilloidea) or S can only persist. Following the latter case, the elaterid folding pattern evolves into or perhaps reverts to the “diversicorn” one (all Byrrhoidea and numerous Elateroidea, Figs A: 73, 76, 80–82, 88–90). Most of the Eucnemidae s.str., Cerophytidae; Trixagus, Throscidae; Lycidae, Omethidae, Lampyridae, some Elateridae, e.g. Drapetes (Lissominae) and certain Agrypninae s.l. are among these elateroids.

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(11) Length reduction of the apical membrane in the course of a generally shortening wing results first in a decline (Lampyridae, some Dascillidae and Buprestidae) and then elimination (most Buprestidae) of the transverse folding component. (12) The development of a stronger abs (Dascilloidea, Buprestidae, Cerophytidae, some Eucnemidae, certain Elateridae, Luciola, Lampyridae; Callirhipidae, Elmidae, Dryopidae), as well as aas' bracing aas–pcas (rp1–RP2) and cpd. The sclerotization aas' is apparently developed to support the wing costal margin distal to cpd during folding; not until this happens that it progresses caudad (all Byrrhoidea, some Elateroidae, “Cantharoidea” included). As it follows from the above, the evolutionary changes in the elateriform wing were not considerable. This is likely due to numerous elateriform beetles retaining through evolution a medium-sized body and often also relatively long elytra. The combination of an initially long basal part and a much shorter apical membrane defined not too considerable transverse folding deformations of the wing supporting axes already in the groundplan. The field C had been extended basad, the transverse deformation were almost eliminated. Additional modifications were AA1+2 shifted onto CuP, and an open 2a. Based on this, a pectinate venation pattern was formed in a large clavus to become a tentatively optimal wing support. An almost total substitution of the fold cq serving as the remigial furrow for the medial flexion-line was another important sequel of the elongated field C. In addition to folding deformations minimized in the wing basal part, the folding pattern was also simplified in the apical membrane, thus not only making the wing less negatively affected by folding than before, but apparently providing some other advantages. An accelerated unfolding of the wing could have become advantageous for Cantharidae as free-living beetles. As the buprestoid folding pattern evolved, the transverse folding component tended to be reduced owing to an increasingly lengthwise ah (Figs A101–104). This change was accompanied by an intense costalization of the wing, which manifested itself in a secondarily elongated cb and a considerably enlarged wing trailing area at the sacrifice of a respectively narrower remigium. The combination of a stiffened costal margin and a shorter wing might have contributed to an increased wingbeat frequency. This, together with the elytra immovable and outspread either horizontally or even vertically in flight (Grodnitsky, 1996), could explain the maneuverable and sudden flight of buprestids. The development of the “dryopiform” folding pattern (numerous Byrrhoidea and a few Elateridae, some smallest Agrypninae and Negastriinae in particular), which is of higher complexity, was necessary to fold the apical membrane grow-

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ing longer as the body got smaller and stouter. The jugal incision (Fig. A80) and sclerotization aas' (Dolin, 1975) are also among the characters which correlated with a small-sized body. Yet the tendency culminating in the former character is much more deeply expressed in Cucujiformia than Elateriformia. Primarily, the Elateridae and the Throscidae among the other Elateriformia show it, those being not only small- (some Negastriinae, Drapetes, Lissominae; Trixagus, Fig. A76) but also medium-sized (Fig. A77; Dicronychus; Potergus, Fig. A75); the latter grouping enlarged perhaps secondarily. As far as aas' is concerned, it is uncertain. This sclerotization is as usual in small-sized elateroids and byrrhoids as in medium- or even big-sized ones (e.g. Eulichadidae, Phyllocerinae, some Agrypninae), being fairly strong in some larger elateriform beetles as well. Hence, if not the presence of aas' proper but a tendency to its development can be recognized as a groundplan feature of Elateriformia. As regards the effect of the miniaturization trend, it could have induced aas' to become sometimes stronger rather than to appear. An allometrically modified venation, a strongly shortened apical membrane and such reversions as a distinct anarc and/or traces of the CuP secondary base (Figs A: 81, 84–86) can be listed among the effects of the opposite trend of size evolution. Elateroidea (Figs A70–92) The wing groundplan combines the elaterid folding pattern (the presence of fields Ia, Ip, a fairly short C and an open D) and the venational groundplan of Elateriformia: veins in clavus and jugum six, “Rr”, cu–a2 and Cur long, cu2 moderately long, 1a and 2a large and contiguous, rc pentagonal and rather short (Fig. A78), RP and m1 bases rudimentary; cw fairly large, not or only slightly smaller, shorter and narrower than scw, situated distal to scw, surpassing its apex by not less than 1/3–1/2 length (symplesiomorphy?). Sclerotization pattern of apical membrane full, three-branched (“trident”), rising from a weak cs; branches share a joint base; of them, at least posterior two branches, RMP and mp2– MP3+4, vein-like (Figs A: 74, 78); mp2–MP3+4 transverse along its basal section (mp2), but longitudinal, more or less parallel to CuA2 (Figs A: 74, 78) over a longer apical section (MP3+4). External border (AA3a") of 2a transverse or at least more transverse than in remaining Elateriformia (synapomorphy). Structure of articular region generally conformable to that of elateriform groundplan; cub wide basally and contiguous to med, with a more or less deep furrow in between. Evolutionary changes in the groundplan were the following modifications, separate or combined: (1) differentiation of pmp, (2) field B substituted for B', (3) field C extended basad, (4) field D closed, with cpd replacing ah, (5) oligo-

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merized fields of central group, (6) a basally open cc, as well as changes in (7) r1 orientation, (8) sclerotization pattern of apical membrane and (9) venation of clavus plus jugum. (1) Several dmp patterns linked together by transitions can be specified using available material. (a) Median plate entire, feebly structured; med and cub delimited by a more (Elateridae: Elaterinae: Ludigenus) or less (Elateridae: Cebrioninae) deep furrow which is arched apicad; cub entire, evenly sclerotized, broad at base, narrower medially and extended into BCu apically. (a1) Same pattern, but the furrow very deep to transformed into a fissure in basal half of pmp (some Elaterinae, e.g. Melanotus). (a2) The furrow barely arched to almost straight, med and cub (sub)contiguous basally (some Elaterinae). (a3) The furrow straight and rather weak, med broadening forward while cub strongly narrowing basad (Elateridae: Lissominae; at least some Eucnemidae, e.g. Phyllocerus) and strongly desclerotized basally in Phyllocerus. (a4) The furrow (if not a fissure) deep and arched apicad, cub broad apically and narrowing basad (Macropogon, Artematopodidae). The entire, almost non-structured pmp of similar shape is characteristic of Cantharidae and, apparently, some Lampyridae. (b) cub divided into two parts, a widely triangular basal part and a narrow apical part, latter directly extended into BCu; the furrow between med and cub either deep or replaced by a fissure (or a narrow window), latter well-developed either basally or all along (Fig. 31) (numerous Elateridae: Agrypninae, Oxynopterinae, Dendrometrinae). Lycidae (Lygistopterus) show the same pattern, but for cub and med merged apically. In the above patterns, the division of cub into two could be recognized only as a more or less distinct tendency. Based on this, coupled with the differences between the patterns specified, one can suggest the pattern of Cebrioninae or Elaterinae to be closer to the groundplan of Elateridae–Eucnemidae. The patterns of Agrypninae + Oxynopterinae + Dendrometrinae seem to be deducible from it while the pmp structure of Lissominae + Eucnemidae from that of Elaterinae. (2) Field B' substituted for B in all Elateroidea but Artematopodidae (Fig. A70). (3) A basad strongly elongated field C is a synapomorphy of Eucnemidae + Throscidae, on the one hand, and the “cantharoids”, on the other. Click-beetles might have developed this character at earlier stages of their evolution. The plesiomorphic condition of the character involved is characteristic of the Artematopodidae alone (Fig. A70), with a slightly derived pattern, namely, a barely elongated field C, being peculiar to Brachypsectridae, Cerophytidae and some Elateridae (certain Dendrometrinae) (Figs 71, 77–78). The remaining dendrometrines, as well as some agrypnines, approach this pattern. Reversals are not observed, certain Elateridae probably excluded.

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(4) An open field D, i.e. without cpde, is a groundplan feature of all the main groups. A closed field D has been developed in Brachypsectridae, Eucnemidae, Throscidae and Elateridae in parallel, and apparently repeatedly, by different members of some of these families. There seem to be no obstacles for considering it as a synapomorphy of “cantharoids” only. (5) The main lineages of Elateroidea having been formed, the “elaterid” folding pattern started simplifying. The fields Ia and Ip were reduced combined in parallel in and within Eucnemidae, Throscidae and Elateridae. The Cerophytidae and probably also the ancestor of “cantharoid” families, except for Omalisidae, Drilidae? and Cantharidae, lost these fields. The combination of reduced fields Ip and S is the main distinction of the latter family (autapomorphy). The folding pattern resultant from the reduction of the former kind, i.e. that composed of the field group C–S–D, is uncharacteristic of Elateridae. Only Drapetes, Lissominae, some Negastriinae and Agrypninae (Figs A80–82) are exceptions, this holding true both of big- and very small-sized agrypnines. The central field group of the elaterid folding pattern is most strongly variable and often also irregular in some Dendrometrinae. Whether this stems from destabilization or, in contrast, the infancy of the pattern is uncertain. (6) A proximally open carpal cell follows the field C extending basad and thus twice intersecting the internal cell border. This accounts well for this vein persisting well-developed in Artematopodidae alone, with its more or less distinct traces only occurring in certain Elateroidea (Figs A: 71, 72, 77, 78, 85, 86; Dicrepidius; Lampyridae: Pterotus: Kukalová-Peck & Lawrence, 1993, fig. 64). (7) A transverse or posterobasad oblique (plesiomorphy) cross-vein r1 is characteristic of Artematopodidae, Cerophytidae, Brachypsectridae, Plastoceridae (Dolin, 2000, fig. 24) and the bulk of the Elateridae. The vein clearly directed posterodistad is hardly less frequent, this condition being primary for “cantharoids” and Eucnemidae, including Phyllocerinae and Perothopinae (apomorphy, Figs A: 72–74, 87, 88, 92). It is also peculiar to Cebrioninae (Fig. A85), Pityobiinae, some Agrypninae s.l. (Figs A: 81, 82; Chalcolepidus, Anthracalaus, Tetralobinae), Elatichrosis (Dolin, 2000, fig. 14) and certain Elaterinae (Fig. A84; Ganoxanthus: Gurjeva, 1979, fig. 84). The fact that most of these elaterids are big-sized implies that r1 so directed must have resulted not so much from phyletic as size evolution, an enlarged body in particular. (8) Changes in the sclerotization pattern can only be represented as tendencies, for the group similarities/differences are not always sharp at the family or subfamily level. “Cantharoids” show the least variable and the most peculiar pattern. It is defined by a combination of the synapomorphies which can be formulated through the presence of two, separate, cloudy sclerotizations more or less

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strongly broadening towards the wing margin. These anterior and posterior integrants of the pattern conform to the strip aas'–aas–pcas and the patch cs– mas–MP3+4, respectively1 (Figs A87–92). Eucnemidae–Throscidae display a little more variable pattern (Figs A72– 76). Its groundplan differs from the elateroid one in nothing else but a distinct abs and a separate aas–pcas. When in conjunction with a more or less distinct cs, either or both these characters occur nowhere else but in “cantharoids” (Fig. A89) or Cerophytidae, respectively. A still greater diversity of sclerotization patterns is observed in the Elateridae, these emerging from the elateroid groundplan through either (1) some of its integrants reduced or (2) new sclerotized patches, abs and/or aas', involved into it, or (3) both. The reduction process starts with the obliteration of a rather weak cs which, nevertheless, persists in a few primitive beetles (Figs A: 77, 78; some Agrypninae). The resultant three-branched pattern composed of aas–pcas, RMP and MP3+4 (Brachypsectridae; numerous Elaterinae, Hemiopinae; Eudicronychus; Anisomerus) then loses RMP, this often (Cardiophorinae, Agrypninae, some Elaterinae; Pityobinae) following or concurring with aas–pcas and RMP–MP3+4 separated (Cardiophorinae, Agrypninae, some Elaterinae; Tibionema). A totally reduced RMP (Cebrioninae, Oxynopterinae: Oxynopterus, Campsosternus, Fig. A86; Tetralobinae, some Elaterinae) results either from its weakened (some Elaterinae, e.g. Melanotus) or attenuated (Brachypsectridae) basal section, or a desclerotized distal section (some Elaterinae; Lissominae, e.g. Austrelater; Cardiophorinae; Agrypninae). The apical membrane totally devoid of a sclerotization pattern is largely characteristic of very small elaterids (Negastriinae, etc.). Irrespective of this, the pattern usually follows a more or less long aas–pcas strip persisting alone (Perothopinae, Eucnemidae; Plastoceridae; Drapetes, Lissominae; Semiotus, Semiotinae: Parreira & Casari, 2004, fig. 13; Oistus). It is the latter pattern that has traditionally been considered as typical of Dendrometrinae. An almost indistinct abs (Figs A77–78) grown into a fairly strong sclerite is among the relatively rare modifications. This sclerite is combined with the apical trident, the latter being full (Elaterinae: Dicrepidiini: Dicrepidius, Anoplischiopsis) or reduced either down to two lateral branches (Elaterinae: e.g. Adrastus, Betarmon; Elatichrosis) or only the anterior one (Protelater, Lissominae). A conspicuous to sclerite-like aas' is a characteristic feature of small-sized elaterids (Negastriinae, some Agrypninae) which are also distinctive in a considerably longer apical membrane (Dolin, 1975). Since this sclerotization serves 1

Constituent parts of cs-mas-MP3+4 are sometimes definable (Fig. A89; Malthinus, Cantharidae).

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to support the field R, the strongest aas' is combined with the “dryopiform” folding pattern (Fig. A80), this being rarely observed in elaterids. Because a well-developed aas' also occurs in medium- (Fig. A79) and big-sized agrypnines, these could have derived from smaller ancestors, as Dolin (1975) believed. In larger agrypnines (Fig. A81; Tetralobinae), aas' can extend anterodistad, thus transforming into a cas which occupies the entire area between the wing costal margin and aas–pcas. In Cardiophorinae and also probably Brachypsectridae, the anterior strip of the apical trident is aas–aas', whereas pcas as the distal part of aas–pcas is totally desclerotized. (9) The venation of the clavus and jugum is much less strongly reduced in Elateroidea than in many other Polyphaga, even the smallest members of the family often retaining at least four veins in the clavus. Exceptions are very few (e.g. Fig. A91; Telegeusis). The main modifications of this groundplan were as follows: – reduction of Cur, with the transformation of cu2 into a new CuP base (Electribius, Artematopodidae: Lawrence, 1995, fig.6; Cerophytidae; Eucnemidae, except for Phyllocerinae and Perothopinae; Throscidae, Fig. A75; “cantharoids”; some small-sized Elateridae: Agrypninae, Fig. A80; Negastriinae; Betarmon, Elaterinae; Nyctor, Dicronychus, Cardiophorinae); – desclerotization of this new base (some Throscidae: Pactopus, Trixagus, Fig. A76); – opening of 2a through desclerotization of AA3a" (Electribius, Artematopodidae; Brachypsectridae; Cerophytidae; most of Eucnemidae, except for Phyllocerinae and Perothopinae; Throscidae; Cantharidae; numerous Elateridae: Agrypninae s.l.; Elaterinae, e.g. Agriotes; Penia, Dedrometrinae; Cardiophorinae); – separation of 1a and 2a by an increasingly long stalk (Cerophytidae; most of Eucnemidae, except for Phyllocerinae and Perothopinae; Throscidae; a greater part of “cantharoids”, Figs A87–89; numerous Elateridae, especially Dendrometrinae and Elaterinae; Aptopus, Dicronychus, Cardiophorinae); – shift of AA1+2 onto CuP following a reduced cu–a2 (all Eucnemidae and Throscidae; some Lampyridae: Photinus, Lucidota: Wallace & Fox, 1980, figs 88–90; Plastoceridae; numerous Elateridae, including all of the Agrypninae; Lissomus, Lissominae; Cardiophorinae; Penia, Dedrometrinae); – a subsequent reduction first of the CuP apical section (Eucnemidae, Fig. A74; Fornax) and then the entire vein (Throscidae, Figs A: 75, 76; some smallsized Elateridae: Negastriinae, e.g. Tropihypnus). The characters resulting from the above transformations are only rarely combined random. The most constant (the most frequent) patterns are as follows.

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The groundplan pattern is peculiar to Elateridae. AA1+2 lying distal to 2a appears to be a little less derived condition than AA1+2 rising from 2a. With some exceptions, the former character is observed in Dendrometrinae, Elatichrosis, Tibionema, Protelater, some Elaterinae, etc. It is also considered here as a plesiomorphy of “cantharoids” and Eucnemidae. The latter character occurs in Plastoceridae, as well as in numerous Elateridae. “Cantharoids” show the pattern which is different from the groundplan by cu2 transformed into the CuP base. This character, together with AA1+2 shifted onto CuP and the tendency towards a reduced 2a, defines what takes place in Eucnemidae, except for Phyllocerinae and Perothopinae, while the pattern in Throscidae is easily derivable from the previous one. All Eucnemidae and Throscidae share only AA1+2 shifted onto CuP. When being the only difference from the groundplan, this character defines Plastoceridae and certain Lissominae. Agrypninae s.l. share it combined with an apically open 2a, this combination occurring rarely in the rest of Elateroidea (Elateridae: Cardiophorinae; Penia). Finally, an apically open 2a, coupled with a distinct cu–a2, characterizes Brachypsectridae, Cerophytidae and Electribius, Artematopodidae. This pattern has also been found in a few click-beetles, primarily Elaterinae. I think that many structural transformations of the elateroid wing have come out of size rather than phyletic evolution. An elongated apical membrane, some supporting elements (veins or sclerotizations) first weakened and then totally reduced, as well as the development of the jugal incision, are among the main effects of adult miniaturization. In contrast, a short apical membrane and the reinforced wing support, with some of the groundplan veins or their parts restored, appear to have been the sequels of the body growing in size. It also seems appropriate to specify particular fulfilments of these general tendencies many of the Coleoptera show. Thus, the tendencies towards a reduced Cur, an apically open 2a, separated 1a and 2a and probably also AA1+2 shifted onto CuP can be referred to as those developed through miniaturization. AA3b persisting long seems to be the only character correlated with a larger body. Some other results of size evolution are a few allometric changes in groundplan venation that are chiefly revealed in the relative position of r1, “r–m” and such a checkpoint as the cpd or CuA2 base. These interrelations can be formulated through the length ratio of “r–m” to mch section between “r–m” and the CuA2 base (or rc posterodistal border instead). When subequally long, the former two veins/sections are here considered as a plesiomorphy. A shorter “r–m” more often occurs in larger elaterids (Figs A: 82, 86), whereas a shorter section of mch in some smaller ones, e.g. Arhaphes, Negastriinae, or Nyctor, Cardiophorinae: Dolin (1975, figs 8 and 17, respectively). The former of these two characters

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is usually supplemented by elongated rc, Mr and Cur, whereas the latter by all these structures seen shortened. Cross-vein “r–m” strongly varies in position relative to the radial cell. This is especially pronounced in the case of a very long rc, its posterior border, RP+MA, ranging from almost absent (Oistus, Hemiops, Chiagosnius) to very long, much longer than the outer cell border (Tetralobus: Dolin, 1975, fig. 11; Pseudotetralobus: Kukalová-Peck & Lawrence, 1993, fig. 65). The latter pattern is an integral part of the wing venation in which allometric changes resultant from body increase reach completion. Both a highly elongated radial cell and the “Rr” strongly extended basad into a distinct remnant of RP are the most prominent of these changes. Byrrhoidea (Figs A93–99) The wing groundplan of the Byrrhoidea is distinguished from that of Elateriformia chiefly by such synapomorphies as a somewhat shorter Mr (apomorphy) and a slightly internal cpd, the latter being the integral part either of an almost elaterid folding pattern of Eulichadidae (plesiomorphy) or the byrrhoid, or “dryopiform” folding pattern. In addition, r1 is either transverse or oblique posterobasad, cu2 is long, field B is secondary, i.e. lying proximal to the area corresponding to cc. The sclerotization pattern of the apical membrane is three-branched (Figs A: 93, 94), but different from the elateroid groundplan in showing a weak MP3+4 and a strong, long and narrow aas' associated with aas– pcas in a V-shaped pattern (Fig. A94). Field C is relatively short, usually not extending to the proximal one-third of the wing basal part measured from the arculus to “r–m” (plesiomorphy). A small and narrow cw is situated frontal to a wide and long scw because of a lengthwise ScP. The external border (AA3a") of 2a is oblique posterodistad. The apical sections of AA1+2 and CuP take off from a shared base due to a reduced cu–a2, except for some Elmidae (Fig. A98) and also probably some Dryopidae. Sclerites med and cub are subequally developed, narrowly separated from each other throughout dmp and extended into BM and BCu, respectively, these latter being fused at their bases (Callirhipidae, Ptilodactylidae). Most of the groundplan alterations can definitely be related to size evolution, chiefly miniaturization. The smaller the adult body, the longer the wing, and the still longer the apical membrane. To fold such a wing effectively, the byrrhoid folding pattern (Callirhipidae, some Ptilodactylidae) evolves into the “dryopiform” one (the rest of Byrrhoidea, except for Byrrhidae and Eulichadidae). Further improvements to this pattern give rise to at least two modifica-

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tions, as follows: (1) cb progressively broadening apically, thus recessing field D from the wing costal margin, and (2) a stepwise decline of the fields C, S and D. These modifications proceed simultaneously with a stepwise reduction of the venation in the clavus and jugum until (3) the only axial bar is retained ending in AAP and supported with 1a or its anterior border basally. What apparently contributes to this reduction is a direct influence of the fold hw which intersects the apical veinal branches lying anterior to AAP. A fall in the supporting function of the veins in the course of body miniaturization also seems to add to the reduction process. The series Ptilodactylidae – Chelonariidae – Psephenidae is the best illustration, with the specialization becoming higher in the series. As a result, the above three modifications reach completion in Eubria, Psephenidae, culminating in the vein (r2+RP1+2)–r2 as the rc outer border running parallel to the wing costal margin. A high-degree reduction of the clavus’ venation is observed in Limnichidae and some Elmidae. MP3+4 reduced to an almost indistinct basal patch is the result of a different general trend. A more or less irregularly folded region around the anterior corner of field S and, consequently, desclerotized posterior and outer borders of rc have been found in the Callirhipidae alone. The latter character stems from the veins directly affected by fold cq or its derivatives in the form of irregular folds of unstable position. A lengthwise field D appears to be its immediate cause, perhaps resulting from a fairly large body in this family. Like in Elateroidea, changes in the structure of the articular region are mainly restricted to the division of an originally entire cub (at least Callirhipidae, Ptilodactylidae, Byrrhidae, Elmidae) into two parts, the basal and apical ones (Parachelichus, Dryopidae). Buprestoidea + Dascilloidea (Figs A100–106) The groundplan. Articular region: posterobasal process of 1Ax considerably longer than posterodistal one; 3Ax head rather slender but strongly bent, with its apex ?truncate; med and cub drawn close to 2Ax, subcontiguous and extended into BM and BCu, respectively. Wing venation almost complete, cw and scw same as in Byrrhoidea, rc rather short, (r2+RP1+2)–r2 conspicuously longer than RP+MA or r1, “Rr” moderately long, Mr long (?secondarily, Fig. A101), a remnant of cc internal border present, cu2 short, Cur well-developed, cu–a2 reduced, both 1a and 2a large, AA3a" strongly oblique posterodistad, AA3b more strongly transverse than in Byrrhoidea. Among the sclerotizations of the apical membrane, only an almost vein-like aas–pcas and a weaker abs well-developed (Fig. A103);

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MP3+4 vein-like and lying close to CuA2, RMP reduced. Folding pattern of a peculiar, buprestoid type, with a widely open field D (Dascilloidea; Schizopodinae, Buprestidae), a fairly short C and a transverse Ia in between; anterior corner of field Ia level or distal to posterior field corner; field B situated proximal to cc (i.e. secondary), A large. The integrity of the groundplan is supported by a greater similarity in the structure of the articular region and wing venation between Dascilloidea and Buprestidae than between either and the other Elateriformia. Shared trends in the evolution of wing venation add to this similarity, with an isolated apical section of CuP (Figs A: 102, 104, 106) being the most illustrative homoplasy. Intergroup differences are minor. These are chiefly restricted to smaller details of the folding and sclerotization patterns resultant from different trends in the evolution of each particular groundplan. Modifications in the folding pattern are certain to have played the leading role in transformations of these groundplans, as follows. In Dascilloidea, the anterior corner of field Ia shifted distal to its posterior corner. Folds dq and de diverged apically, first due to an increasingly lengthwise de, with sclerotizations abs and aas–pcas following the latter fold. In acquiring a (sub)apical position, aas–pcas tended to be reduced (Fig. A102) and superficially replaced by abs, the latter getting vein-like. In contrast to Dascilloidea, some apicad shift of the field Ia posterior corner, if at all, brought about no change in the groundplan sclerotization pattern (Buprestidae, Fig. A106). Thus having been formed, the wing groundplans of Dascilloidea and Buprestidae evolved in the following directions. (1) Reduction of the folding pattern. A lengthwise field D (Fig. A102–106) fails to provide an efficient transverse folding. Hence, it can be recognized as the first evolutionary response to a strongly shortened apical membrane which thus no longer requires length reduction during folding. When coupled with long and narrow elytra (Fig. A106), all of the major closed fields can persist. However, in numerous Buprestidae they grow narrower until reduced to rudimentary folds of ambiguous polarity. As a result, the wing support strengthens. The wing becomes more strongly costalized through a considerable forward shift of CuA–CuA2, with the respectively broadened clavus plus jugum, as well as first a shortened and then disappearing “r–m”. An additional vein emerges from a postero-apically open 2a (Figs A: 105, 106) to support an extended clavus and also provide it with additional flexibility. Both isolated anals and the CuP apical section seem to contribute to the flexibility of the clavus plus jugum as well (Fig. A106). (2) Restoration of the transverse folding. This seems to be the only acceptable explanation for the presence of field S instead of Ia in some Buprestidae with

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comparatively short elytra, e.g. Anthaxia. Thus, the former field is very likely to be no field S proper but an analogue of this field once reduced. (3) Reduction of rc is observed in some buprestids (Fig. A106). This results from (r2+RP1+2)–r2 first approaching and then merging into the anterior cell border composed of the RA distal section. When combined with a lengthwise or reduced field D, either the product of this fusion or RA can strongly extend apicad (Figs A: 102, 106), sometimes forming cas where fused with the pcas distal part (Fig. A104). (4) Reduction of abs accompanies the folding pattern in decline, especially field D which encloses this sclerotization (numerous Buprestidae).

The cucujiform wing This wing type covers the hind wings of all Polyphaga, except for Scirtoidea, Staphyliniformia s.l. and Elateriformia s.str. The groundplan combines an almost full wing venation and the “diversicorn” folding pattern with an open field D. The main venational synapomorphies are the following totally reduced integrants: m3 (perhaps merged into “Rr”), cubital joint, cu–a2 (persisted pointlike only in Peltastica, Derodontidae), AP3b, axial cord and carpal cell. A fairly short and wide rc bearing the radial spur (rsp), a conspicuous remnant of anarc, and a well-developed, vein-like rms are rather to be considered plesiomorphies. The sclerotization pattern of the apical membrane is full and apparently close to the groundplan of Polyphaga. Of its three branches, the posterior one, MP3+4, is especially strong, more or less vein-like and connected with “r–m”. The anterior branch (aas–pcas) and an apically shortened medial branch (mas = RMP) are much weaker and thence liable to further transformations or reduction: mas more often is replaced by an anteriad shifted MP3+4, with pas usually developed behind. The portion of ams situated proximal to “r–m” is rather strongly sclerotized, thus resembling a rudimentary vein (perhaps MP1+2). The above plesiomorphies are scattered among different polyphagan taxa. In particular, a rudimentary anarc occurs in Dermestes, Dermestidae, Mordellidae and Endecatomidae. Chrysomeloidea, some Curculionoidea (Cimberis, Nemonychidae), Ericmodes, Protocucujidae, and Stenotrachelidae possess the “r–m”–rms unit of the most primitive structure. A penta- or, more seldom, tetragonal rc with a distinct rsp is peculiar to some Cleroidea, Chrysomeloidea, Curculionoidea and Mordellidae. The latter family also shows the least derived sclerotization pattern of the apical membrane. An open field D, i.e. cpd not formed yet, is only observed in a few tenebrionoid families (Stenotrachelidae, Mordellidae, Rhipiphoridae), as well as individual Cucujoidea (Byturidae).

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Derodontoidea (Figs A107–109) The wing of Peltastica, Derodontidae, is here recognized as the groundplan. Wings of the other derodontoids are derivable. Wing rather narrow, with subequally long basal part and apical membrane; jugal lobe small, jugal incision moderately deep. Venation typical of the cucujiform wing: rc of moderate size, “Rr” moderately long, Mr short, rms rudimentary but distinct, MP3+4 well-developed and indistinctly connected with “r–m”; venation of clavus and jugum nearly full: CuP almost reaching wing margin, both 1a and 2a large, AP4 conspicuous; cu–a2 point-like. Among sclerotizations of the apical membrane, aas and a rudimentary pas present. Secondary features are as follows: cb broadened apically; “Rr” beginning on “r–m” due to a reduced apical section of RP+MA and caudally fused r1 and r2 (r2+RP1+2); cu2 and anarc reduced, MP3+4 somewhat shifted anteriad, wing costal margin distal to cpd supported by a strongly sclerotized strip, this being supposedly composed of fused cas and aas–pcas. Folding pattern of the “eudryopiform” type, with fields D, R and H detached from wing margins; secondary apical hinge well-developed. Fold hw intersecting CuA2 about midway. Fields A, B, C and G large (plesiomorphy). All or at least most of the above venational apomorphies are certain to have resulted, both directly and indirectly, from miniaturization, being mediated by the development of the “dryopiform” folding pattern in the latter case. Further decrease in body size in the series Peltastica – Laricobius – Derodontus – Sarothrias caused the “eudryopiform” folding pattern to evolve into the curculionid one and invited the venation to be stepwise reduced. As the clavus decreased in size, the CuP basal part was obliterated while 2a became almost indistinct along with AAP and AA3a'. A hairy fringe grew much longer over the wing margin, especially the posterior one, to compensate for a strongly reduced wing membrane as the wing working area. The apical membrane also became much less strongly sclerotized or pigmented. At the summit of these alterations (Sarothrias, Jacobsoniidae), the wing trailing area disappeared while only two strongly reinforced axial bars, cb and CuA, were retained to support a very short basal part of the wing. At last, the folding pattern was modified into the “postdryopiform” one, fields S and D having been reduced down to a single indistinct fold each, with field R losing its function. Folding was thus simplified to ternary: the longitudinal folding along folds cq–la and cw–x3 was first followed by the transverse folding along the e2–hx–hw line and then by the very wing apex folded. The sclerotizations of the apical membrane were reduced down to a very narrow strip, ams – base of MP3+4, and two small patches lying frontal to the base of field Xh which supported the SV base.

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Bostrichoidea (Figs A110–125) All the diversity of wing types in Bostrichoidea can be reduced to two principal ones. Of them, the groundplan is only peculiar to some Dermestidae (Dermestes, Attagenus, Orphilus). It is quite conformable to the cucujiform wing, from which it only differs by wanting rms and rsp, a closed field D (cpd well-developed), field A replaced by Af as one of its two daughters, and probably also a slightly basad extended field C. The remaining bostrichoids show the wings which can be referred to as belonging in an obviously derived, bostrichoid, type chiefly definable by the characters of very special folding patterns, including trends in their evolution. This bostrichoid folding pattern is largely distinguished by the combination of a concave ahII and an internal and doubled cpd; for convenience, the former can be recognized as fold dq. Another convex fold (e3) next to dq differentiated from the remaining folds of the anterior part of the apical membrane as the “probostrichoid” folding pattern (Figs A: 121, 122) developed. The presence of cpdi makes this pattern similar to some variants of the “dryopiform” type, but ahII is concave in the former, versus convex in the latter. Conversely, the combination of folds dq– and e3+ draws the “probostrichoid” folding pattern and some of its derivatives much closer in appearance to the folding patterns whose integral part is a widely open field D, these being the scirtoid and dascillid patterns, as well as several variants of the “diversicorn” folding type. However, the latter similarity means nothing, since it concerns non-homologous structures, folds dq and e3 in the former case against folds dq and de=e1 in the latter. The development of the “probostrichoid” folding pattern results in field C growing broader and shorter from its base, field B enlarged and increasingly transverse, as well as G strengthened and often also split into a few daughter fields, with fold hw usually progressively turning basad. Some other results are an increasingly elongated ahII and a transformed groundplan venation. Thus, the RA apex drifts apart from the wing costal margin while rc opens basally through an anteriorly reduced r1 (Anobiidae) and/or “Rr” shifts onto “r–m” following rc decreased in size (Endecatomidae, Bostrichidae, some Anobiidae: Eucradinae, Ptininae). Field B growing stronger invites the proximal costal pivot (cpp) to partly revert. As a result, the RA posterior part at the field B corner grows weaker while its anterior, rigid part is supplied with an oblique convex fold ending in fold bp. Fields B and A (or Af) combined affect Mr so that it gets much shorter from the base. CuA2 under the pressure of fold hw becomes either more transverse or intersected by this fold (Figs A: 113, 114). An increasingly long apical membrane gets reinforced with SV anteriorly (this either combined with cas or not) and a somewhat forward shifted MP3+4 posteriorly. It is a hy-

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pertrophied field G that seems to have caused the venation of the adjacent area V to grow weaker or partly reduced (Figs 115, 119). Be it so or not, the most strongly reduced venation of the clavus is observed in Bostrichidae (neither cu2 nor the CuP apical part, nor the AA3a' base) rather than Anobiidae, culminating in AAP retained alone (Lyctus). A characteristic excurvation of “r–m” where MP3+4 grows away is to be added to the modifications as above. MP3+4 is strong just distal to “r–m” and thence similar to rms which is absent or rudimentary in the groundplan (Fig. A114). The posterior end of “r–m” sometimes approaches the CuA2 base (Figs A: 118, 122, 124). The above transformations largely stem from the evolution of the folding pattern, this being multidirectional, but determined by the shared tendency towards numerical reduction of the closed fields. The fields merge in different combinations through folds being reduced in between. Some or, rarely, all of thus formed fields can then decline, either disappear or open up. The megatomine wing type (Anthrenus, some individuals of Megatoma) is defined by the nominate folding pattern distinctive in the presence of an open field distal to the secondary apical hinge. The field has resulted from the fusion of fields D, R and a small portion of field E lying proximal to fold e3 (Fig. A113). The “anobiid” folding pattern of the anobiid wing type came out of the following transformations. Fields D and R grew smaller as ahII became longer. On the contrary, fields C and S extended up to the posterior wing margin. The posterior (superficially distal) corner of field B migrated progressively anterodistad, thus leaving field C strongly reduced proximal to “r–m”. This hypothetical pattern has not persisted per se, but it could have given rise to two daughter ones. The first (Ernobiinae, Anobiinae, Ptilininae, Xyletinae, Figs A115–117) emerged from fields C and S fused into a single field, combined with fields D and R either retained rudimentary (e.g., Xestobium, Ptilinus, Xyletinus) or merged into fields C+S and H, respectively, due to reduction of fold dp and the proximal section of fold la (Figs A: 116, 117). Similar transformations took place as the second pattern was formed (Ptininae, Eucradinae, Figs A: 118, 119). Its main distinction is a reduced field C added by some other derived characters following this reduction. In particular, the field B occupying a special position, namely, its posterior (superficially distal) corner lying distal to “r–m”, suggests that the reduced field C should have been preceded by the development of a secondary fold (b'q) running distal to the fold bq and flowing into the proximal corner of field S+D. Hence, the field C is very likely to have been reduced through concurrent reductions of folds bq and cw, with fold cq persisting. Having extended into fold bw, the latter fold became a constituent part of the posterior border (b'p) of a new field B', with folds b'q and bp forming the other two field borders.

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The first derivative of the anobiid folding pattern is only slightly different from the nosodendrid pattern. This is distinctive in having two closed fields, C+S+D and R+H combined, each almost retaining the aggregate shape and size of nearly all primary fields, except only for field H which became closed since the tips of folds hx and cw met. As a result, fields C+S+D, R+H and the proximal portion of field E limited by the folds e2, e3 and ahII=dq resemble fields C, S and D in the scirtoid wing or C, S and the proximal part of field D+R+E in some dermestid wings, respectively (Fig. A113); this makes the nosodendrid, scirtoid and megatomine folding patterns very similar. The folding pattern of the bostrichid wing type (Figs A120–125) seems to have been formed otherwise: two complex fields, C+S+H and R+D1, have appeared, the former large, the latter small and tending to be reduced (Figs A: 123–125). I think that all or at least many of the above modifications in wing venation and, especially, folding patterns have resulted from size evolution. First the “probostrichoid” and then the megatomine and anobiid folding patterns seem to have been evolutionary responses to apical membrane elongation consequent upon the body growing smaller and/or stouter. In contrast, the bostrichid folding pattern may have emerged from some size increase of a formerly smaller body. This also means that the bostrichoid wing type as formulated above is rather functional than structural. It is defined by the characters developed in parallel in different Bostrichoidea, at least Dermestidae, on the one hand, and the remaining Bostrichoidea, on the other; therefore, this type is heterogeneous. The character set shared by all Bostrichoidea is restricted to venational characters as follows: (1) MP3+4 adjoining “r–m” (plesiomorphy), (2) MP3+4 strengthened just distal to “r–m” (apomorphy), and (3) “r–m” contorted at its juncture with MP3+4 (apomorphy). Lymexiloidea (Figs A126–129) The wing groundplan (Fig. A126) fits in well with that of Tenebrionoidea, yet much more derived in some characters. In particular, there are no rms, CuP distal part, sub-cubital binding patch, sclerotizations cs and mas in the wing. “Rr” is almost indistinct. Sclerotized strip aas–pcas and MP3+4 are involved into a C-shaped pattern. The following plesiomorphies also deserve mention: a traceable rsp (Fig. A128), a rather long Mr, a long and posterodistad oblique

1

Field R+D is almost indistinct in Bostrichus or completely reduced in Tristaria.

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

cu2, as well as a distinct Cur. The folding pattern is of the “serricorn” type (Figs A126–128). The subsequent modifications in the groundplan have arisen from the transverse folding becoming obsolete in response to a strongly elongated adult hind body. Transformations started with an apically open 2a, such a cell being constantly present in Melittoma, only occasionally on one or both wings of Elateroides, but never in Atractocerus. Adaptations to fan-folding were as follows: (1) development of jointed folds cq–dq– and cw–hw+, both of rigorously axial orientation; (2) increasingly lengthwise folds, including newly formed ones, in the clavus and jugum; (3) respective change in supporting axial bars, namely, CuA–CuA2 and (AA4+AP1+2+AP3a)– AP3a lining up; (4) transformation of the jugal sclerotization into a secondary vein to support the posterobasal wing margin; (5) cb extended to the wing apex; (6) rc open through its outer border reduced. A few radiating folds between folds de and la were also involved in folding the apical membrane. Lymexilidae are the most similar to Melandryidae and, especially, Stenotrachelidae (cf. Figs A126 and A131) primarily in sharing a nearly identical venation pattern of the clavus, namely, an almost straight vein (AA1+2+AA3a)–(AA1+2+AA3a')– AA3a', a long and posterobasad directed cu2, as well as 2a of a particular shape. Tenebrionoidea (Figs A130–184) The wing groundplan is quite conformable to that of the cucujiform wing. Hence, the particular groups of Tenebrionoidea differ from the other Cucujiformia only by separate polythetic characters. Among them, the most constant are as follows: (1) a rather short apical membrane, combined with a long and wide clavus + jugum, (2) the latter combining an isolated sbp and a nearly full venation, except for a wanting cu–a2 and a free apical part of CuP, (3) a welldeveloped sclerotization pattern of the apical membrane, with mas and pas usually well-developed, (4) the “diversicorn”, mostly “serricorn”, folding pattern prevailing. The groundplan. Wing moderately wide, with a large jugal lobe and no jugal incision. Venation: rc fairly short (Figs A: 130–133, 144, etc.), “Rr” and “r–m” more or less widely separated from each other (Figs A: 132, 133, 144–146, 156, 158), “Rr”, Mr and cu2 long1; Cur distinct (Figs A: 130–133, 135, 140, 143, 1

A long Mr can be termed a plesiomorphy when it is combined with a basad nonextended field C (Dytilus, Stenotrachelus and some Tenebrionidae, Figs A: 130, 141, 158, 159).

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146, 158–162, 167, 168), rms as a fairly long and truncate vein (Figs A130– 132), both MP3+4 and the remnant of anarc conspicuous (Figs A134–137), 1a and 2a large (in most families). Set of anals full, CuP associated with subcubital binding patch (Figs A: 153, 174). Posterior branch (AA1+2+AA3a') of a Y-shaped pattern bracing CuP–AA1+2 and 2a strictly lengthwise, directly extended into AA3a', longer than and perpendicular to anterior branch (secondary base of AA1+2) of the pattern (Figs A: 130–133). A rather short apical membrane is combined with the “clavicorn” folding pattern: fields A and B large, A and C sharing only one corner, C not extended basad (Figs A: 133, 141, etc.), D widely open (Figs A130–138), thence no cpd. The sclerotization pattern of the apical membrane is full, composed of ams, abs, aas, pcas, cs, mas and pas (Figs A: 134, 140). The structure of the articular region is usual to Cucujiformia: 2Ax arm (BR) well-developed; med extended into BM, latter fused with BCu where intersected by fold bf–jf and narrowly separated from BCu distal to the fold; cub divided into two parts, proximal and basal, former triangular and broad at base, latter rudimentary and merged into BCu. The main trends in the evolution of the groundplan: Different tenebrionoid families show a pronounced tendency towards a retained or even enlarged jugum. However, this in the first place holds true for big- or medium-sized beetles, whereas a considerable decrease in body size induces the opposite tendency, as a rule. The axilla is not or only a little transformed. Its principal modifications are chiefly three. Firstly, a transverse corrugation is developed either all over BCu or, in many taxa, only over its distal part. Secondly, BM gets reduced down through being desclerotized or merged into BCu. Finally, cub becomes totally reduced distally. The 2Ax arm (BR) disappears only exceptionally (e.g. Campsiomorpha, Tenebrionidae). Wing venation: (1) Optimization of the remigium’s support results in a gradual reduction of supporting elements such as rms, “Rr”, Mr and rc. At first, rms merges into ams while “r–m” adjoins an increasingly short but still long “Rr” (Figs A: 131, 136– 138, 159, 160, etc.). The next step is “Rr” shifted onto “r–m” and thus remote from r1 since r1 and r2+RP1+2 merged caudally (Figs A: 134, 135, 171). Strongly to completely reduced “Rr” and rc follow this change while rc either opens internally (some Melandryidae or Pyrochroidae, Fig. A170) or grows increasingly small as r1 and (r2+RP1+2)–r2 further merge from behind (Figs A: 154, 155). This culminates in only two retained supporting bars, cb and CuA–CuA2, which are braced by “r–m” apically; the latter vein is extended forwards and backwards into merged r1 and (r2+RP1+2)–r2 and a small anterodistal fragment of mch, respectively (Figs A: 177, 178). Similar patterns are observed in some

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Melandryidae (e.g. Abdera) and Anthicidae, as well as Aderidae, Scraptiidae, Anaspis, Ischaliidae, Pterogeniidae and Salpingidae, Othniinae included. (2) The clavus’ venation tends to be simplified same as in many other Coleoptera. The free apical section of CuP was reduced in all of the Tenebrionoidea, except only for some colydiine zopherids and pterogeniids. As a result, the pattern composed of four anal apical branches, combined with a separate sbp, became a groundplan feature of most tenebrionoid families. Further modifications in the pattern involved were as follows: (1) cu2 reduced or transformed into a CuP secondary base following an obliterated Cur, (2) reduced anal cells, (3) AA3a' shifted onto AA1+2 (Figs A134–139, a few Melandryidae: Melandrya caraboides; Salpingidae: Prostominia, Sphaeriestes, probably also Elacatis; some Tenebrionidae: Cossyphus, Catapiestus, etc.), (4) oligomerization of the anal veins, including their apical branches, through either reduction both of CuP– AA1+2 and the Y-shaped pattern or a stepwise shortening of AP3a (Figs A: 143, 160, 177, 179, 184; some Salpingidae: Istrisia) until the latter vein is absent (Figs A: 145, 155, 161, 181, 183; Salpingidae, e.g. Prostominia, Sphaeriestes). The anal cells disappear either simultaneously or, more often, 1a following 2a like in many other Coleoptera. When the latter takes place, the anterior and posterior borders of 2a gradually approach each other until merging (Figs A130–133). This way of reduction seems to have also been realized in Mordellidae and Rhipiphoridae. The other two pathways start with a reduced external border (AA3a") of 2a, thus leaving the cell wedgy and situated proximal to the Y-shaped pattern (Figs A: 150, 151, 154, 169–171, 176, 178). Then 2a may have evolved following two directions. Usually, it gets reduced first in size (Figs A: 140, 143, 147, 153, 184; Melandryidae: Xylita) and then totally (Figs A: 149, 155, 174, 175, 182, 183; some other Salpingidae, Colydiinae; Hypulus, Melandryidae; Hallomenus, Tetratomidae) as the anterior and posterior borders of the cell increasingly merge basad. More rarely, 2a opens up caudally along a short distal section of the cell posterior border first (Figs A: 176, 178) and throughout the border (AA3b+AA4+AP1+2) after (Figs A177; Melandryidae: e.g. Dircaea). Because of its weak posterodistal border (AA4+AP1+2, Fig. A151), 1a is capable of opening up along this vein not only simultaneously or after 2a (some Mycetophagidae: Litargus; Triphyllus, Pseudotriphyllus: Nikitsky, 1993, fig. 2), but also before it (Fig. A184; Tydessa, Pyrochroidae). Strongly reduced venation patterns of the clavus are chiefly peculiar to small-sized beetles (Ciidae, some Salpingidae and Tenebrionidae: some Diaperinae; numerous Anthicidae, etc.), in which the clavus and jugum are either strongly reduced in size and separated by a more or less deep jugal incision or the jugum is totally reduced.

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A succession of venational reductions in the clavus and jugum is well-traced in some families whose venation patterns range between the groundplan and a single or no longitudinal vein supporting a narrow clavus, combined with no jugum. The Salpingidae taken as example, these patterns can be illustrated by the series Salpingus (full venation) – Istrisia (AA1+2+AA3a' shifted onto AAP) – Rabocerus (a reduced 2a; AA3a' shifted onto AA1+2) – Sphaeriestes (elongation of the interfluence zone between AA3a' and CuP–AA1+2; AP3a reduced) – Prostominia (a caudally open 1a; reduced AAP and AA3a') – Inopeplus (one or no veins in the clavus). Similar transformation series arranged for some other families are distinguished from the above by either differently reduced anal cells or the loss of the Y-shaped pattern, or a shortened CuP, or a combination of these characters. Vein AP3a undergoes reduction for a variety of reasons. The vein is certain to have disappeared in small-sized beetles as the clavus plus jugum increasingly reduced. Yet a strongly shortened or lacking AP3a also occurs in numerous larger beetles. Repartition of the wing trailing area between the clavus and jugum for the benefit of the latter might have accounted for this (Figs A: 143, 145, etc.). This process also led to drawing the longitudinal veins in the clavus together, leaving the anal cells reduced in width or totally. Folding pattern: (1) Closing of field D, with the development of the distal costal pivot (cpd), seems to have occurred during the early evolution of the superfamily. As a result, only Stenotrachelidae and Mordellidae–Rhipiphoridae (Figs A130–139) show this field widely open, i.e. only the apical hinge is present. An almost closed field D is occasionally observed in Boridae (Fig. A157) or individual members of Tenebrionidae (?secondarily, Fig. A160). (2) Evolution of the “clavicorn” pattern into the “serricorn” one results in a basad strongly extended field C, combined with partly to completely reduced fields A and B (Figs A: 142–146, 149, 154, 155, 167–170, 176–184). Field C grows in length not so much by itself as by the posterior part of field B as its basal extension. Accordingly, the middle part of B actually becomes inserted into a newly formed, complex field composed of field C distally and the posterior part of field B proximally (Fig. 38). (3) Development of the salpingid folding pattern from the “clavicorn” one (Figs 174, 175; also Prostominia). (4) Evolution of the “clavicorn” folding pattern into the elaterid one (Fig. A143). The latter pattern is only found in Serropalpus, implying its rather having been formed occasionally, perhaps owing to a lengthwise field D. (5) Evolution of the “clavicorn” folding pattern into the “dryopiform” one (Figs A: 150–152, 161; Sphaeriestes, Salpingidae; Zopheridae: Pycnomerus, Bitoma, etc.) is a gradual alteration. It performs through an intermediate stage either of the

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“hemidryopiform” (Figs A: 154, 164, 173) or salpingid (Fig. A174; Prostominia) folding pattern. This is accompanied by the apical part of cb, which ends in the anterior border of rc, increasingly large and detached from the wing costal margin. The “hemidryopiform” pattern not only gives rise to the “eudryopiform” one, but it itself evolves into the “postdryopiform” pattern (Figs A164–166). This happens due to the special combination of a strongly internal cpd and a missing cpdd, i.e. a quite free fold e2 (Fig. A164). As a result, field R merges into area Q following a reduced field D, with fold e2 as ahII substituting for cpd. In such a way, the diaperine folding pattern (Fig. A164) is upgraded in the series Diaperis – Leiochrodes – Pentaphyllus. The sclerotization pattern of the apical membrane, including vein MP3+4: (1) MP3+4 shifted forwards, and more lengthwise in addition, occurs in a number of tenebrionoid families, being a distinction of the tenebrionid lineage. This modification is conspicuous in Tenebrionidae, Prostomidae and Synchroidae, less so in Ulodidae, Zopheridae (Colydiinae), Boridae and Stenotrachelidae. A lacking to indistinct (supposedly reduced) mas, combined with a prominent and often also strip-like pas, is another characteristic feature of the pattern involved. (2) A reduced MP3+4 is observed in numerous Melandryidae and Oedemeridae (e.g. Oedemera, Dytilus) in which MP3+4, mas and pas merge into a wide, but weak and diffuse sclerotized patch. On the contrary, Pyrochroidae (Pyrochroa, Schizotus) and its allies (Mycteridae, some Anthicidae, Ischaliinae included, Scraptiidae) show the combination of a reduced MP3+4 and reinforced mas and pas. (3) Development of the aas–pcas unit. The characters that underlie this pattern, namely, the length of the apical membrane, as well as the shape of fields D and R, vary considerably across Tenebrionoidea. This obscures the strict homology of the pattern’s constituent parts in different members of the superfamily. The sclerotization pattern close to the groundplan (Figs A134–136) starts transforming following aas directly extended forwards into aas'. A strengthened aas' is peculiar to numerous Tenebrionoidea (Figs A: 131, 133, 140–142, 144–146, 153, 154, 157–159, 162–166, 169–171; Ulodidae). In some of them, e.g. Synchroidae or some Melandryidae, the strip aas–aas' seems to also involve pcas. In most other cases, pcas disappears as aas–aas' develops, but sometimes it persists as a distinct strip (Mycteridae). An association of subequally developed aas–aas' and pcas occurs in Anthicidae, Scraptiidae, Aderidae and Anaspididae. Besides this, it is separated from cs–mas owing to a reduced aas base which is also characteristic of Pyrochroidae and certain Melandryidae (Fig. A145). Finally, some other tenebrionoid taxa are defined by the presence of the strip aas–pcas alone; either both of its constituent parts are subequally developed (Figs A: 148, 151, 156, 172, 173, 175) or aas is stronger (Figs A: 149, 150).

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The above three patterns are very labile and thus capable of greatly transforming even under insufficient changes in the wing folding pattern, shape or size, or in the length ratio of the wing’s basal part to apical membrane. More specifically, when combined with a very long apical membrane, aas–aas' can evolve into a very strong sclerite fused to the cb apex (Fig. A166) while pcas into a strong strip (Figs A: 164, 166), the latter being largely uncharacteristic of Tenebrionidae. Altogether, most of the Tenebrionoidea have the wings which are not profoundly transformed as compared with their groundplan. Modifications in the basic venation, folding and sclerotization patterns have largely been partitive and, as a rule, they only concerned some constituent parts of each pattern, with fundamentally different wing types occurring rather occasionally. In particular, the apical membrane growing longer, as well as the clavus and jugum decreased in size, all consequent upon adult body miniaturization, were followed by increasing reduction of some supporting elements, veins in particular. The folding pattern rarely transformed cardinally. It either persisted within its basic, “clavicorn” type or was modified into the “serricorn” one. Patterns of the “dryopiform” folding type were not too frequent, the “postdryopiform” ones much less so (Fig. A166), found only in several tenebrionids. The elaterid folding pattern seems to have been an exception (Serropalpus alone). There is also a wing type of some Rhipiphoridae (Fig. A139) among the most advanced tenebrionoid wings. The wing is somewhat narrower and a little more strongly costalized than in more primitive rhipiphorids and mordellids studied. The other characteristic features are as follows. Firstly, the costal bar is reinforced with a strongly elongated and narrowed rc. Secondly, the remaining major supporting elements such as aas–pcas, MP3+4 and CuA2 are almost lengthwise. This also holds true for veinal stems reduced down to three in number in the wing trailing area, as well as all folds, except for an almost reduced field S. Accessory supporting elements such as “Rr”, Mr, “r–m” and the anal cells are wanting same as are fields B and A. The wing membrane is thick and strongly corrugated throughout its length except in the jugal lobe. Given the high, 120 Hz wingbeat frequency observed in some mordellids (e.g. Mordellistena tournieri: Grodnitsky & Morozov, 1994; Grodnitsky, 1996) and the close affinity seen between Mordellidae and Rhipiphoridae, many of the above features seem to have been wing adaptations to working with higher beat frequencies. A reduced transverse folding component appears to have not only been among these adaptations, but also something that preconditioned them. Some small-sized diaperine tenebrionids show hardly less strongly transformed wings (Fig. A166). This transformation is revealed in many wing char-

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acters and directly resulted from the adult body growing smaller and stouter. These changes gave rise to a much longer apical membrane and thence a profoundly modified folding pattern (see above). Another result was an increasingly strong strip aas'–aas–pcas, with its differentiated constituent parts, which started serving to support both the apical membrane’s anterior part and field R involved in area Q following field D reduced in between. Having given rise to SV, the strip pcas disappeared while a hypertrophied aas–aas' fused to the cb apex, thus leaving field R immovable. The clavus venation evolved independently and thence not too considerably: chiefly cu2 and the free section of CuP or AA1+2 were lost; mostly both anal cells persisted, albeit 2a often strongly reduced in size; two or only one (AAP) longitudinal vein survived, with the remainder obliterated (Fig. A165). Cucujoidea (Figs A185–209) It is the Cucujoidea among the Coleoptera that shows the greatest variety of wing types. This seems to be largely due to the great taxonomic diversity, as well as the predominance of small or miniature beetles in the superfamily. Small-sized beetles are always distinctive in having both the entire wing and its integrants advanced. Thus, long wings prevail, with a very long apical membrane, a small to lacking jugal lobe separated from the clavus by a deep jugal incision, a strongly reduced venation and a weak sclerotization pattern of the apical membrane. However, all derived wing types must have emerged from nowhere else but the cucujiform wing type. Hence, the apical membrane appears to be primitively rather short, occupying 20–35% of the total wing length. The clavus and jugum are fairly short, without jugal incision in between. Wing venation is full: “Rr” and Mr of moderate length, rc modestly large, indistinctly pentagonal; rsp only traceable, i.e. a slight prominence is present just posterior to the anterodistal corner of rc; therefore, r2–RP1+2 almost substituting for r2, thus forming the outer border of rc (Figs A: 185, 202); ams still small because rms is welldeveloped, vein-like, beginning on an angulate “r–m” (Figs A: 185, 186). Cur and cu2 distinct but short (Fig. A202); 1a and 2a large (Figs A190–192). An oblong sbp separated from CuP and seemingly weak. Presumably, pas is originally present (Figs A: 188, 189, 202) while abs is weak or indistinct (Figs A: 186, 191, 192); MP3+4 is distinct and shifted forward, thus almost completely replacing mas (Figs A: 185, 186). Folding pattern of the “clavicorn” type (Figs A: 186, 189, 191, 203). The groundplan seems to have evolved in the following directions:

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Folding pattern: (1) Development of the “serricorn” pattern seems to have been an earlier evolutionary tendency that invited a strong elongation of field C basad (Fig. A: 190, 193–195). The tendency manifested itself chiefly in medium-sized to larger beetles (Cucujidae, Passandridae, Silvanidae, Helotidae, Languriidae). However, this pattern also occurs in some small-sized (perhaps secondarily so) cucujoids (Laemophloeidae, Propalticidae, Bothrideridae), its combination with a very long apical membrane (Figs A: 196, 197) being uncharacteristic of Coleoptera. (2) The “dryopiforn” pattern has been developed by representatives of numerous groups as an evolutionary response to a growing apical membrane length. Like in other Coleoptera, this pattern passes through a few successive stages until completed. The “eudryopiform” pattern (some Endomychidae and Coccinellidae, Corylophidae, Lathridiidae, Cerylonidae, certain Erotylidae: Leucohimatium; some individuals of Bothrideres, Figs A: 206, 207, 209) gives rise to the coccinellid variant (Fig. A208; Aphorista: Forbes, 1926, fig. 127) of the curculionid folding pattern. The cryptophagid variant (Figs A: 198, 199) of the latter is likely to have stemmed from the salpingid one found in some Silvanidae (Silvanus). (3) The monotomid pattern (Fig. A200) is supposed to have been derived from near the cryptophagid one. (4) The nitidulid pattern (Fig. A201) is likely to have become an immediate derivation of the “diversicorn” pattern, albeit very similar to the previous one. Wing venation: In general, wing venation becomes simplified. The radial cell of plesiotypic size or shape survives in few, usually larger beetles (Figs A: 185, 186, 188–192, 194, 202). In the remainder, rc gets small, often loses its inner border and finally transforms into a pigmented patch at the cb apex; “r–m” is either fragmented or missing. Cross-vein cu2 and an almost indistinct Cur become obliterated, thus leaving CuP remote from CuA. However, “Rr” and Mr often persist long enough even in fairly small beetles, except for the smallest. (1) The cubital spur (CuA2) gets movable since intersected at its base by the fold hw. Such a spur is the main distinction of the wings with the cryptophagid, monotomid and nitidulid folding patterns. Rarely, it accompanies the diversicorn folding pattern (Fig. A203; certain Erotylidae: Cryptophilus). (2) Reduction of the clavus venation. The complete veinal set, i.e. that composed of five apical branches, occurs in few cucujoids (Figs A: 185, 186, 193–195, 198, 199; Priasilphidae). In the remainder, these veins could reduced down to four (Figs A: 188–192, 200, 203) or three (Fig. A201), resulting from CuP and/ or AA1+2 disappeared. Sometimes AP3a was involved in the reduction process (Figs A: 204, 205), culminating in no or only one longitudinal vein in a very narrow clavus, this being coupled with a totally reduced jugal lobe (e.g. Cerylonidae).

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Longitudinal veins seem to have undergon reduction in two principal ways, depending on a particular groundplan at bottom. The first groundplan was composed of two strong, more or less straight veinal trunks such as (AA3+AA1+2)–AAP and (AA4+AP1+2)+AP3a, combined with much weaker CuP, AA1+2 and AA3a' (Figs A193–195; probably also Figs A: 198, 199, 205). As this pattern grew weaker following an increasingly small adult body, only vein (AA3+AA1+2)–AAP tended to be retained (Figs A: 196, 197). The second groundplan (Figs A: 188, 189, 204) consisted of a single strong supporting bar which was reinforced basally with a rather large 1a or the 1a–2a unit and bent S-shaped medially, with the apical veinal branches subequally well-developed. It is following these branches reduced, namely, AA3a' and AAP, that the clavus’ venation was “simplified” (Figs A206–209). (3) Reductions of 1a and 2a. The 2a gets reduced through its anterior and posterior borders merging as the cell grows either increasingly small (most cucujoids) or narrow (some Erotylidae: Leucohimatium, Cryptophilus). Sometimes, 2a, together with 1a, shifts basad (Figs A: 188, 189). The 1a can lose its posterodistal border (Fig. A199; Bunyastichus, Phloeostichidae: Leschen et al., 2005, fig. 64), with the posterior border sometimes also desclerotized (Fig. A201). This pathway of reduction seems also to account for many other strongly reduced venation patterns in the clavus (Laemophloeidae, Propalticidae, Cerylonidae, Corylophidae, Lathridiidae, etc.). (4) Evolutionary fate of sbp. The sub-cubital binding patch strongly varies in appearance from well-expressed (Figs 185, 186, 188, 189, 191, 192, 200; some Cerylonidae, Lathridiidae) to lacking (Figs A: 193, 196, 197, 198, 201–205; some Cerylonidae and Monotomidae; Discolomatidae). I leave the question open whether the fleck is a groundplan feature or not, so the transformation series for some families remain uncertain. For instance, the fact that sbp is missing in Passandridae and Laemophloeidae, but present, albeit weak, in Cucujidae and Silvanidae can be considered either as a development or degeneration, depending on the approach used. Cryptophagidae/Phloeostichidae is a similar couple. In certain families such as, e.g., Cerylonidae, sbp is either present or absent. A (totally) reduced sbp is explicable only for the wing with a long apical membrane and a movable cubital spur combined. As this pattern could have been formed, the wing grew narrower, with its basal part becoming much shorter. Accordingly, the fold hw turned progressively basad until area V was too small to allocate such a relatively large structure as sbp. Following this evolutionary scenario, I recognize sbp as a groundplan feature of at least two groups, Phloeostichidae, Priasilphidae and Cryptophagidae, on the one hand, and Monotomidae, on the other. However, given the fleck present in the wings

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of a much more primitive structure (Protocucujidae, Sphindidae, Byturidae, Biphyllidae, Erotylidae), it seems possible to apply this hypothesis to the entire superfamily. In Endomychidae and Coccinellidae, sbp is capable of changing in position and/or shape. In particular, when originally associated with CuP (or CuP–AA1+2) and lying close to the CuA2 apex (Fig. A206), a large sbp sometimes tends to be caudally reduced and separated from CuP, not CuA2 (Figs A207, 208). This may have partly come out of a secondarily enlarged adult body. Sclerotization pattern of the apical membrane: Transformations of the sclerotizations inside the field unit D–R/S–H are sure to have been caused by the development of the “dryopiform” folding pattern. The primary sclerotizations abs and aas, as well as mas and a section of MP3+4 inside field H, strengthened, some of them transforming into tight sclerites. Vein MP3+4 lost its base and merged into mas, thus becoming a direct extension of cs. This also resulted in the posterior corner of field S shifted caudal to this “new” MP3+4 (Figs A207–208). Thus, in spite of the great variety of wing types in Cucujoidea, the development of the folding pattern seems to have been the main and primary trend in the evolution of the cucujoid wing groundplan. This trend gave rise to numerous variants of the “clavicorn”, “serricorn”, “dryopiform” and even staphyliniform folding types, this variety being greater than in any other polyphagan superfamily. Most of these patterns were adaptations to folding a long to very long apical membrane consequent upon a decreased body size. Yet the miniaturization trend only triggered off certain morphogenetic processes leading to a longer wing, a much longer apical membrane and the wing venation in decline as wing support. This induced the folding pattern to be improved, with the wing support adapting both to folding and flight. Solutions to the problem were numerous and depended on a particular wing groundplan. The differences between these groundplans often faded as parallelisms, venational reductions first, accumulated in the course of groundplan evolution. The wings of extremely small-sized beetles with the “eudryopiform” folding seem to serve as the best illustration. Usually, they are distinctive in having no jugal lobe, a narrow clavus supported with the only longitudinal vein, a long and almost depigmented apical membrane, a very short basal part of the remigium with cb and CuA–CuA2 in support, and a large sub-cubital binding patch. Wings of such a derived structure resemble one another very closely, a number of Cucujoidea (some Endomychidae, Lathridiidae, Cerylonidae) being hardly if at all different from certain Tenebrionoidea (Ciidae). Some secondary increase in body size results in a not (Passandridae) or only slightly (some Coccinellidae) modified folding pattern, leaving the supporting axes of the apical membrane (MP3+4, SV1 and SV2) reinforced.

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Chrysomeloidea, Curculionoidea and Cleroidea Representatives of these three superfamilies are distinctive among the groups sharing the cucujiform wing type in having a particular wing groundplan. This is highly stable due to the following character combination: (1) folding pattern of the “clavicorn” type; as a result, (2) “Rr” and Mr subequally rather short and usually convergent basad; (3) abs strengthened up to a sclerite, mostly a tight one; (4) ams rather strong, Y-shaped, developed well on both sides of “r–m”, latter angulate at its middle whence a vein-like rms starting; (5) Cur very short to indistinct; (6) mas very narrow or lacking; (7) MP3+4 adjoining “r–m” basally and strengthened at least apically, (8) sbp mostly missing. At least two more or less steady tendencies also deserve mention, one towards a reduced free apical section of CuP (Chrysomelidae, all or at least most of Cleroidea, almost all Curculionoidea), the other towards a reduced association of cu2 with the CuP basal part following this small basal fragment (cu2–CuP) detached from CuA (some Chrysomeloidea, most of Curculionoidea, all Cleroidea). This wing type is very close if not identical to that of primitive cucujoids, especially the Protocucujidae. The latter seems to fit in with it even better than the Cleroidea does. Cleroidea (Figs A225–236) The wing groundplan is defined by the following character combination: (1) five apical veinal branches in clavus, (2) both 1a and 2a large, (3) pas present, (4) folds of fields E and X sharing a common base with fold e2, (5) cs weaker than abs, (6) a sclerotized bridge between rc, abs and cs absent or indistinct, (7) “r–m” straight, without vein-like rms, (8) sbp lacking, (9) basal part of CuP short and remote from CuA, (10) posterior corner of field S situated caudal to MP3+4. In addition, field Af substituted for A seems to have been a very early evolutionary trend. The former five characters are shared by Cleroidea and Chrysomeloidea, (1) and (2) or (1–3) are symplesiomorphies, whereas (4) is of uncertain polarity. Character (1) is a plesiomorphy of Cleroidea and Curculionoidea while (7–10) are synapomorphies of Cleroidea, character (10) being also characteristic of Byturidae–Biphyllidae. As regards character (1), almost all Cleroidea are known to show four apical veinal branches in the clavus, but five veins have repeatedly been recorded in Necrobinus, Korynetinae, Cleridae (Crowson, 1955, fig. 91; Wallace & Fox, 1980, fig. 176). Perhaps it is the latter pattern that is to be considered plesiomorphous.

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The groundplan survives almost without change in Trogossitidae s.l., Cleridae and Prionoceridae, except for a few venational modifications. More specifically, rc first evolves from penta- (Fig. A229) into tetragonal and then gets small (Figs A225, 234) to missing (Tenebrioides), resulting from r1 and r2+RP1+2 merged caudally. 2a tends to be reduced as well. It opens through its anterior border (AA1+2+AA3a) increasingly shortening from the base (Figs A: 229, 230). More rarely, the 2a external border (AA3a") grows weaker (Fig. A231) until lacking (Trichodes, Tenerus). The basal part of CuP (Tenebrioides) or the secondary base of AA1+2 bridging CuP–AA1+2 and AA3a' (Grynocharis) are among the other veins liable to reduction in the clavus. The folding pattern alters subtly. Usually it progresses not farther than the “hemidryopiform” type (some Cleridae, Figs A: 228, 230) while evolving into the “eudryopiform” one rather occasionally (Melyridae: Dasytinae: Pristocelis, Listrus – Forbes, 1926, figs 122 and 123). Trogossitidae tend to reinforce the area around cpd, thus leaving the wing costal margin more strongly sclerotized frontal and distal to field D. This short cas, as well as a rather strong aas' caudal to it, merges into a joint sclerotized patch extending caudad to MP3+4 (Figs A: 225, 226). The anterior component of the patch (cas) is well-developed in Tenebrioides, whereas a separate, but rather strong central fragment is observed in Thymalus, more or less well corresponding to aas'. Much deeper transformations of the wing groundplan occurred in Melyridae, this groundplan being distinguishable from that of Cleroidea only by weaker veins between CuA–CuA2 and AAP, strongly shortened “Rr” and the CuP base, as well as a basally wide mas. In particular, the “clavicorn” folding pattern (Fig. A232) was stepwise modified into the melyrine (Fig. A235) or malachiine (Fig. A236) variants of the melyrid type. The venation and sclerotization patterns were transformed accordingly. Already at the stage of the “protomelyrid” folding pattern mas became well differentiated from MP3+4 while the radial cell grew smaller consequent upon caudally fused r1 and r2+RP1+2 (Fig. A234). When hypertrophied in Melyridae, mas could be interpreted at least alternatively, based on (1) there being no well-developed mas in Trogossitidae and Cleridae, as well as (2) field S situated frontal to MP3+4 only in some Melyridae. Perhaps a larger mas is a plesiomorphy (Fig. A231). However, when very strong, mas seems to be secondary, being composed either of the MP3+4 basal section distal to field S or this section fused with the true mas. This complex mas might have developed as vein MP3+4 acquired its secondary base now lying caudal to field S and also often shifted towards or even onto the CuA2 base (Fig. A234–236). Wing venation tends to be somewhat reduced in the clavus. 2a disappears either through its fused anterior and posterior borders or perhaps opening up

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anteriorly (Fig. A233). Some veins partially dissolve or shorten (Figs A: 234, 236). The radial cell still persists as strongly modified in the wing with the malachiine folding pattern, but disappears in that with the melyrine one (Fig. A235), accompanying the cb apex incrassate and strongly curved caudad. A notably modified wing shape follows a strongly to completely reduced jugal lobe. Phytophaga (Figs A210–224) The wing groundplan integrates the following main plesiomorphies: pentagonal rc, vein-like rsp, apical veinal branches five in the clavus, and the “clavicorn” folding pattern (this is slightly modified into the “hemidryopiform” one in Belidae and Nemonychidae, Curculionoidea). Synapomorphies are few: a particular shape of the structural unit composed of rc, a vein-like but short rsp, and the cb apex (Figs A: 211, 215, etc.); rc, abs and cs bridged by a sclerotized strip with one another, association of SV1 with SV2 of characteristic structure, shape and position; cs sclerite-like. These characters are also supplemented with a few evolutionary tendencies which add much to the similarity between numerous representatives of Curculionoidea and Chrysomeloidea. The following peculiarities come out of these shared tendencies: aas tight and triangular (Figs A: 214, 217– 219), pas lacking (Fig. A214; all Curculionoidea), the cu2–CuP fragment first detached from the main part of CuP (Figs A: 214, 217) and then reduced (Figs A: 213, 216), a movable CuA2 (Fig. A214; most Curculionoidea), a sclerotized strip between SV1 and SV2 (Figs A: 211, 213, 214, 218, 221) evolved into TV (some Curculionoidea), well-developed icsp and icsa (Figs A: 213, 216, 221, etc.), as well as derivatives of field A of similar shape and position (cf. Figs A213 and A220). Chrysomeloidea (Figs A210–214) This wing type is almost conformable to the wing groundplan of Phytophaga, differing in the following characters: an unmodified “clavicorn” folding pattern, folds of fields E and X and the fold e2 starting from one point, a more or less distinct pas, secondary “vein” SV0 beginning on SV1 base, both 1a and 2a large, sbp sometimes present. The wing type is almost invariable, except for wing venation modified in the clavus or certain veins reduced. When present, these modifications include the transformation of a tetragonal rc into a triangular one, with rsp reduced; rms sometimes obliterated, a straight and short “r–m”, both “Rr” and Mr shortened or, more rarely, wanting; a simplified venation in clavus.

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2a disappears either through its proportionate decrease in size (some Chrysomelidae s.l.) or through the anterior and posterior borders merged (numerous Cerambycidae, some Chrysomelidae s.l.). Veins get reduced in the clavus likewise in various taxa in spite of some basic differences (these rather operate as tendencies) between Cerambycidae and Chrysomelidae s.l. Most of Cerambycidae retain the groundplan venation, namely, five apical veinal branches in the clavus against only four, because of an early reduction of CuP, in the great majority of Chrysomelidae, Orsodacnidae and Megalopodidae included. At the next stage, AA3a' shifts onto CuP–(CuP+AA1+2)–AA1+2. This is followed by a two- or, rarely, three-branched vein (cu2–CuP–) detached from AAP due to a bridge (AA1+2+AA3a') reduced in between. Under the direct influence of field G or its derivations, that vein then tends to fragment into the main part and a small basal remnant composed of cu2 and the proximalmost section of CuP at best. The apical branches of the vein involved, CuP–AA1+2 and AA3a', become quite well separated since the remnant is obliterated along with their shared base. The sequence of the above morphogenetic stages is often upset. For instance, numerous Chrysomelidae (e.g. Chrysomelinae) show first AA3a' shifted onto CuP–AA1+2 and only then the cu2–CuP remnant and vein AA1+2+AA3a' reduced in succession. In addition, some Chrysomelidae and Megalopodidae tend to reduce AP3a (Fig. A214). The combination of a lacking 2a and the inversely directed posterodistal border (AA4+AP1+2) of 1a is a distinctive feature of some lamiine cerambycids (e.g. Acanthocinus), this occurring nowhere else within Coleoptera except for some Malachiinae (Fig. A236). Curculionoidea (Figs A215–224) All of the Curculionoidea are very similar in wing structure and can be linked together into a chain. The groundplan venation is nearly full: rc pentagonal, with a short but distinct rsp (Belidae); “r–m” angulate whence a short but veinlike rms starting (Fig. A216; Anthribidae); five apical veinal branches in clavus; aas missing or indistinct (Belidae; Fig. A216). The anterior half of the apical membrane is reinforced with “veins” SV1 and SV2, these being less strongly sclerotized than the adjacent parts of the wing membrane. CuA2 is associated with icsp. Field G is large. The jugal fold strongly tends to be replaced with a secondary fold lying frontal (distal) to it. The groundplan is distinguished from that of Phytophaga as follows: there are no 2a in any representative but a few relicts; the curculionoid folding pattern of the “hemidryopiform” type is present; pas is missing; fold e2 is separated from

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the folds of fields E and X. This wing type is the most similar to the wings of some Cucujoidea (Fig. A185) and Chrysomeloidea (Fig. A214). The Belidae among the remaining Curculionoidea shows the least derived folding pattern (Fig. A215). This follows first from the combination of large and long fields H and R, a still open R and a rather short Xh whose posterior fold is not parallel to the anterior one (la). The most primitive wing venation emphasizes the basal position of Belidae. A little shorter fields R and H, combined with a conspicuously elongated Xh whose anterior and posterior folds are lengthwise and run parallel to each other, seem to have corresponded to the next evolutionary stage (Figs A: 216, 222). First a doubled costal pivot (Fig. A218) and then one internal became further two evolutionary steps. These were accompanied by fields S, D, R and H progressively diminished in size, with field Xh growing longer. This process culminated in the brentid folding pattern, resulting from the total reduction of fields D and S (Fig. A224). The folding pattern of Nemonyx (Fig. A217) is noteworthy. It is peculiar since fold e2 and those of fields E and X radiate from one point, like in the chrysomeloid or cleroid wing. However, the combination of a short and triangular field Xh and a distinctly shortened apical membrane argues this pattern to be derived. That Cimberis shares the wing folding pattern with the other curculionoids (Fig. A216) is evidence of this being the case. The curculionoid wing whose integral part is a long field Xh folds more effectively when field X incorporates the wing regions caudal to CuA2. A much more deformable CuA2 is necessary to accomplish this, with the following two contributing modifications, separate or combined. These are CuA2 shortened apically and CuA2 crossed by a fold basally. When shortened, CuA2 is extended into a reinforced icsp probably to compensate for the loss of a supporting function both in flight and folding. This immediately invites numerous unstable folds and small fields to appear around CuA2–icsp, these folds being separate or associated with field G. The venational groundplan must have evolved in the following way. The radial cell became invertedly trapezoidal first and triangular after. The former change was due to a strongly to completely reduced r2 while the latter to “Rr” shifted onto “r–m”. The radial spur (rsp) persisted as at least traceable (Figs A: 217, 219, 220) until r2 reduction. The radiomedial spur (rms) disappeared, leaving “r–m” increasingly unbent and shortened. When strongly approaching r2, cross-vein r1 was followed by “Rr” shifted onto “r–m”, as well as a much smaller rc of rectangular shape (Fig. A222). In the clavus, the apical section of CuP first detached from CuP+AA1+2 and then disappeared (all families but Belidae). The rest of CuP split into two parts, these being a rather short proximal remnant, cu2–CuP, and usually a longer

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distal section of CuP. AP3a shortened (Nemonychidae) and then obliterated (all Curculionoidea, except for some Attelabidae). 2a underwent reduction at a very early evolutionary stage. It persisted as a small remnant only in certain Belidae (Atractuchus: Zherikhin & Gratshev, 1995, fig. 38). In the remaining Curculionoidea, 2a seems to have been reduced through being proportionately decreased in size. An open external border of the cell was also probable (some Belidae, e.g. Homalocerus: Zherikhin & Gratshev, 1995, fig. 39). The reduction of veinal branches in the clavus follows AA3a' shifted onto CuP+AA1+2 (Curculionoidea but Belidae)1. The division of the CuP basal part into two fragments, with further reduction of either or both, coupled with an obliterated shared base of the two anals anterior to AAP, results in only one strong axial bar (AAP). The latter is accompanied by two, short, mostly separate, apical sections of AA1+2 and AA3a', either or both of which strongly tend to disappear. A posterodistally open 1a, with its posterior border growing shorter basad, concurs or terminates the reduction process. AP4 degenerates as the jugal lobe decreases in size. The groundplan sclerotization pattern could have evolved in the following way. As the central fields decreased in size, width first, the sclerotizations cs, mas and the base of MP3+4 were compressed inside. A tight abs was developed into a narrowly transverse triangular sclerite. The antero-apical sclerotization (aas) seems to have emerged as a novelty, perhaps from a nearly indistinct caudal part of the aas proper. It is either a tight triangular sclerite (Attelabidae, Anthribidae, Urodontidae) or a wider area inside field R, the area being either homogeneous (Fig. A217; Oxycraspedus, Oxycorynidae: Zherikhin & Gratshev, 1995) or sclerite-like anterodistally (Allocorynidae, Aglycideridae: Zherikhin & Gratshev (1995); Ithyceridae; Curculionidae)2. The secondary “veins” that reinforce the apical membrane grow increasingly lengthwise. The longer the membrane, the more lengthwise the “veins”. Of them, SV1 becomes the major while SV2 can disappear (Fig. A224). Either SV1 and SV2 or SV1 alone get reinforced through the area growing stronger in between. The resultant sclerotized strip becomes increasingly vein-like, thus evolving into a slightly concave tertiary vein (TV), versus the convex SV.

1

2

This pattern looks pectinate forward in many attelabids, implying a retained AA1+2. This, however, is highly unlikely to have been the case because, when well-traceable, the vein AA3a’ does grow away from CuP+AA1+2 (Exrhynchites: Zherikhin & Gratshev, 1995, fig. 78). The Brentidae in which wings a sclerite-like aas occupies the entire field R is likely to be placed among the latter families.

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In the most specialized wings, the icsp distal part hoops forwards and shifts frontal to a short CuA2 (Figs A222, 224) while cs–mas and ams merge into a narrow sclerite (Fig. A224). As it follows from the above, it is the changes in the folding pattern that underlay many of the transformations of wing venation and sclerotization pattern. Wing venation, primarily that of the clavus and jugum, became strongly simplified while the sclerotization pattern, on the contrary, complex. As abs, aas and mas, coupled with the MP3+4 base, were broadened and/or modified into strong sclerites, they formed a stronger support to the fields D, R and H, respectively. SV1 or the SV1–TV association constituted the support of the anterior part of a strongly elongated apical membrane. Thus, the morphological adaptations of the curculionoid wings to apical membrane elongation were similar to those observed in most other cucujiform beetles, with the groundplan combination of field Xh and the “hemidryopiform” folding pattern being a distinctive feature of Curculionoidea.

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MORPHOLOGICAL EVOLUTION OF THE BEETLE HIND WING AND THE PHYLOGENY OF COLEOPTERA Nobody doubts that character-limited systems and phylogenies are far from perfect. However, I believe that the affinity between particular beetle groups can be clarified from an analysis of beetle wing structure like in many other pterygotes. At least some hypotheses concerning interrelations of higher beetle taxa will be put forth to be verified elsewhere within a comprehensive phylogenetic analysis. Figure 57 shows some results obtained. Despite their great diversity, the wing patterns of the Coleoptera differ strongly from those of the other insects, but fit in well with a particular wing type, implying that the Coleoptera is a monophyletic taxon. The beetle wing groundplan as here reconstructed (Fig. 15) seems to be the closest to that of Myrmeleontidea, especially Megaloptera (Figs 12–14), the wing venation of the clavus plus jugum of some Chauliodinae, Megaloptera, and the Adephaga, Coleoptera, being almost identical (Figs 24–27). The main venational difference between the Megaloptera and the Coleoptera is the arculus being mp–cua in the former, versus m–cua (apomorphy?) in the latter. The relationships between Recent Archostemata, Adephaga, Myxophaga and Polyphaga are ambiguous, so they have been interpreted very differently. The former three suborders show the wings largely conformable to the archostematan wing type, albeit slightly deviating. The wing of Polyphaga, on the contrary, is a profound derivative of the latter type which seems to have been the closest to the groundplan of the Coleoptera. That the Adephaga (Figs 17; A1–27) and the Myxophaga are very similar if not identical in wing structure, yet sharply contrasting with Polyphaga (Figs 20, 21), suggests with good reason that the former two taxa are much closer to each other than either to the latter. Based on this, the Polyphaga and the Myxophaga seem to be not too close relatives, sisters in particular, as some authors believe (Klausnitzer, 1975; Baehr, 1979; Beutel, 1997; Beutel & Haas, 2000). The similarity between Recent Archostemata (Figs 18; A: 19, 20) and Adephaga in wing structure is largely based on symplesiomorphies, the rich

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Figure 57. Phylogeny of Coleoptera based on hind wing structure.

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wing venation and the folding pattern close to the original one being among them. What also points to the archaism of the Adephaga is a very primitive structure of the elytron since the latter has retained vein-like bases of odd intervals on the undersurface, as well as the alula, i.e. a rudimentary jugal lobe, with a distinct vein AP4. Archostemata show a larger number of derived character states than the Adephaga does, among them: neither the CuP primary base nor the MA basal section, the complex arculus due to M–MP shifted onto CuA, a shortened and strongly narrowed primary pterostigma, short and wide radial and oblong cells, no radiomedial spur, and the costal joint instead of the costal bending zone. Moreover, the regular apical roll of the archostematan wing cannot be totally excluded as being a derived character either. The former four characters anyway seem to be synapomorphies of Recent Archostemata and the Polyphaga. The latter suborder is defined by the combination of such autapomorphies as a missing CuP base, the radial spur, triangular fields C and S, and a reduced CuA1. A particular sclerotization pattern of the apical membrane may probably be an apomorphy as well. When treated alternatively, namely, as composed of rudimentary veins, this pattern, combined with the entire axial cord, a distinct vein AP3–AP3b and the complete venation of the clavus (except at base), i.e. with an almost caraboid venation, point the Polyphaga to be a rather archaic group. Hence, the relationships between the extant coleopteran suborders seem better to be defined (Adephaga + Myxophaga) + (Archostemata + Polyphaga) or Adephaga + Myxophaga + (Archostemata + Polyphaga). They are likewise interpreted by Ponomarenko (2002), but for one difference. Thus, this author derives not only the Adephaga and the Myxophaga, but also the Micromaltidae from extinct schizophoromorph Archostemata (Asiocoleoidea, Rhombocoleoidea, Schizophoroidea), opposing the latter to the Cupedomorpha comprising Polyphaga, Cupedidae, Permocupedidae and Tshekardocoleidae. Schizophoroidea (Schizophoridae, Catiniidae) are distinguished among the Archostemata by a strongly derived wing structure. If this be attributed to all of the Schizophoroidea, no extant Coleoptera could be derivable from the Schizophoroidea. This thus disagrees with Ponomarenko’s (1969, 1977) hypotheses, according to which the Adephaga and the Myxophaga emerged from the schizophoroid lineage. The wing of Micromaltidae also fails to fit in with the schizophoroid wing type. It seems to be better considered as a cupedid wing, albeit with a strongly reduced wing venation. The subdivision of the Polyphaga into two lineages, the hydrophiloid (Staphyliniformia + Scarabaeiformia) and eucinetoid ones, the latter lineage comprising the remainder of the suborder (Kukalová-Peck & Lawrence, 1993), also seems to require corrections or at least comments. More specifically, the

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most primitive polyphagan wing is that of Scirtoidea because it combines the caraboid venation, including a distinct carpal cell and no “Rr”, as well as a large field B and a still open field D. Due to this character combination, the scirtoid wing folds about in the same way as that here supposed to have been the groundplan of the Recent Coleoptera. Based on this, the Scirtoidea could have been considered as a link between Archostemata, Cupedomorpha in particular, and the other Polyphaga. Therefore, the placement of the Scirtoidea beyond the Elateriformia, with erecting it into a separate series (Crowson, 1971; Lawrence, 1988), seems quite appropriate. The remaining Coleoptera, including Haplogastra, are thus to be recognized as stemmed from near Scirtoidea. What could have represented a link between Haplogastra and Scirtoidea was Sikhotealinia Lafer, 1996, Jurodidae? (Kirejtshuk, 1999). The wing of this beetle (Fig. A30) is distinguished by a unique character combination. Namely, the folding pattern is advanced much farther than the folding patterns of not only cupedomorph archostematans, but also the Scirtoidea. It approaches the “dryopiform” folding pattern, still corresponding to the staphyliniform wing type in all essential details. These are subequally large, quite closed fields S and D, a short field C with its proximal and posterior tops shifted forwards and backwards, respectively, a large field A and the CuA2 intersected at its base by the fold hw (or its derivative). The wing venation is much more ambiguous. In general, it is of the cantharoid type, but retains a number of highly archaic features. In particular, “Rr” may have not been formed yet because a rudimentary but independent RP+MA base and a remnant of m3 seem to be retained. There also occur a rudimentary but still visible oblong cell and an almost full venation of the clavus plus jugum in the wing: apical veinal branches are six, both anal cells are large, anarc is well-developed while the CuP secondary base is distinct, albeit very short. This pattern differs from that of some Cupedidae (Fig. A29) by only a few characters, among them: cu–a2 obliterated due to AA1+2 shifted onto CuP, CuP reduced between its secondary base and cu2, as well as anarc situated proximal to AA3b, the latter character being typical of Polyphaga (and Adephaga), not Archostemata. Granting that Sikhotealinia is a real polyphage, not an archostematan with a far advanced wing structure, its position within Polyphaga can be interpreted in at least two different ways. Thus, if “Rr” be recognized as a synapomorphy of Polyphaga but Scirtoidea, the Jurodidae should be placed closer to Scirtoidea. In contrast, the combination of primarily folding synapomorphies points to the affinity between Sikhotealinia and no other polyphagan group but Haplogastra. As far as the Scarabaeoidea is concerned, no character has been found to keep this superfamily within Haplogastra. That the wing of the lamellicorn beetles looks like a derivative of the hydrophiloid wing agrees with Hansen’s (1995, 1997) logical assumption of the close affinity between the Hydrophiloidea and

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the Scarabaeoidea. The separate series Scarabaeiformia thus seems unnecessary. In such an extended treatment, the Staphyliniformia, or the Haplogastra, or the hydrophiloid lineage, displays no close relationships with the other Polyphaga. Its sclerotization pattern of the apical membrane is only a little similar to that of the remaining Polyphaga while the elytron of some Hydrophilidae retains a distinct alula like in Adephaga. The clavus’ apical veinal branches reduced down to four is a character shared by Staphyliniformia s.l. and Scirtoidea. This character, however, has been developed by many other coleopteran taxa, so it is underweight both phylogenetically and taxonomically. The remaining Polyphaga can be considered as more or less closely related to Scirtoidea, Scirtidae in particular, since both share a highly characteristic sclerotization pattern of the apical membrane. It is noteworthy that the Scirtoidea is much more similar in this character to all polyphagan series than to Elateriformia proper (i.e. excluding Scirtoidea). The Elateriformia s.str. seems to have descended from ancestors which had the folding pattern similar to that of Artematopodidae. The Buprestoidea (+ Dascilloidea), the Byrrhoidea and the Elateroidea s.l. each is distinguished by a particular wing structure, folding pattern included. The elaterid, byrrhoid and buprestoid folding patterns are the groundplans of Elateroidea plus Eulichadidae, Byrrhoidea but Eulichadidae, and Buprestoidea plus Dascilloidea, respectively. The peculiarities of the buprestoid folding pattern and a great similarity both in wing venation and the structure of the axilla strongly support the close affinity between Buprestidae and Dascilloidea, thus in good agreement with Lawrence et al. (1995a). Byrrhoidea and Elateroidea seem natural, Eulichadidae being annectent. The occurrence of the elaterid folding pattern in Omalisidae argues against the former division of Elateroidea in its extended treatment (Lawrence & Newton, 1995) into Elateroidea proper and Cantharoidea, which some authors have recently appealed to (Dolin, 2000). The other superfamilies of Polyphaga show very similar wing groundplans, including the folding pattern of the “clavicorn” type, the wing venation and the sclerotization pattern of the apical membrane. Phytophaga, Cucujoidea and Cleroidea seem to be a little closer inter se.

Relationships of individual beetle taxa based on hind wing structure Adephaga The above uniformity of the adephagan wings and a considerable character transgression combined obscure a reconstruction of the phylogeny of the

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Adephaga using wing characters alone. The phylogenies proposed to date based on numerous imaginal and larval characters are often conflicting. There are two principal hypotheses competing with each other. According to the first, the Gyrinidae is supposed to be the sister to the remaining Adephaga (Ochs, 1926, 1969; Beutel & Roughley, 1988; Beutel, 1991), with the latter lineage being treated either as Haliplidae + (Dytiscoidea + Geadephaga) (Beutel, 1993, 1995, 1998) or (Haliplidae + Dytiscoidea) + Geadephaga (Beutel & Haas, 1996). Ponomarenko (1973) arranges higher adephagan taxa likewise: Gyrinidae + Haliplidae + (Dytiscoidea + Geadephaga). The more traditional hypothesis (Crowson, 1960; Ponomarenko, 1977; Roughley, 1981; Lawrence & Newton, 1982; Kryzhanovskij, 1983) proclaims Recent Adephaga to be subdivided into two monophyletic groups of infraoder or series rank, Hydradephaga Macleay 1825 and Geodephaga Macleay 1825 (= Geadephaga auct.), this being in good agreement with the results of molecular research (Shull et al., 2001; Ribera et al., 2002). Most authors currently recognize the monophyly of Geadephaga (Ponomarenko, 1977; Kryzhanovskij, 1983; Beutel & Haas, 1996; Shull et al., 2001; Ribera et al., 2002), as well as sister-group relations between the Trachypachidae and the Carabidae (Ponomarenko, 1977; Erwin, 1985; Kavanaugh, 1986; Beutel & Haas, 1996). However, hypotheses still persist that (1) Trachypachidae and Dytiscoidea are closely related (Ward, 1979; Beutel & Roughley, 1988; Beutel, 1993, 1995, 1998; Arndt & Beutel, 1995) and (2) Rhysodidae are nothing else but derived Carabidae (Bell & Bell, 1962; Erwin, 1985, 1991; Bell, 1998; Maddison et al., 1999; Ober, 2002). Three lineages, Haliplidae (Haliploidea), Dytiscoidea and Gyrinidae (Gyrinoidea), are hypothesized within Hydradephaga as having descended either from different riparian ancestors (Bell, 1966) or an aquatic one (Ponomarenko, 1977). The latter viewpoint is followed by Kryzhanovskij (1983), with the reservation that the Gyrinidae stands apart from the remainder. Such a position of Gyrinidae within Hydradephaga is almost always noticed, Gyrinidae being set against Hydradephaga either separate (Baehr, 1979) or combined with Haliplidae + Noteridae (Burmeister, 1976; Ruhnau, 1986). At present, Crowson’s (1960) hypothesis implying two adaptive radiations, the earlier (Haliplidae + ((Amphizoidae + Hygrobiidae) + ancestral Dytiscidae)) and the later (Dytiscidae + Noteridae + Gyrinidae) ones, cannot be accepted. A different model, Gyrinidae + (Haliplidae + (Noteridae + (Amphizoidae + Dytiscidae, including Hygrobiidae))), has resulted from molecular research (Ribera et al., 2002). The most conflicting are the interrelationships within Carabidae and Dytiscoidea. For the latter group, they are often defined as Noteridae + (Amphizoidae + (Hygrobiidae + Dytiscidae)). Nevertheless, the Amphizoidae was

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hypothesized to be closer to Hygrobiidae and, especially, the Haliplidae or the Carabidae, based on similarity in the macro- and microstructure of the pygidial defensive glands (Forsyth, 1968, 1970). Kavanaugh (1986) treated Hygrobiidae as the sister to Gyrinidae, whereas Dettner (1985) considered both these lineages as quite independent, thus emphasizing Forsyth’s (1970) query about the shared ancestor of Hygrobiidae and Dytiscidae. The similarity was also noted between Haliplidae and Noteridae, on the one hand, and Dytiscinae and Colymbetinae, on the other, in the composition of defensive secrets of the pygidial gland (Dettner, 1985), as well as between Laccophilinae and Hydroporinae in structure of the prothoracic glands (Forsyth, 1968). Gyrinidae. The wing groundplan mostly integrates plesiomorphies. Among them, the oblong cell of primitive shape, combined with a long CuA2 (Orectochilus) and a very long AP3b, is unique while the remaining traits also occur in some other Adephaga. In particular, a longer axial cord and m3 are shared by many adephagan groups. Much less frequent are a longer rms (Dytiscinae, Dytiscidae), a conspicuous basal part of MA (Eretes, Dytiscinae) and a rudimentary primary base of CuP (Dytiscidae, Carabidae). Vein AA1+2 rising from 1a (combined with 2a retained) can be considered either as a plesiomorphy or an autapomorphy (see above) because no other Adephaga show this character, but Haliplidae could be exception to the rule, were it not for 2a absent. The remaining derived characters seem to have emerged to improve flight and wing folding. Among these, there are synapomorphies, rather homoplasies: a more or less hexagonal cc, m3 shifted distal to rc (Gyrinus, Porrorhynchus) and then reduced, both cu–a2 and the secondary base of CuP lacking. The apical wing roll of Gyrinus appears to be an apomorphy, too. This character set can be enlarged due to an almost reduced cw, with Spanglerogyrus (Kukalová-Peck & Lawrence, 1993, fig. 15) being the only exception. The polarity of character states in some transformation series is far from clearcut. A particular position of rf seems to be a rather weak autapomorphy if not a plesiomorphy. The polarity of presence/absence of the sub-cubital binding patch is also disputable, same as is the position of the cubital joint. But even greater difficulties appear when ordering the overlapping/non-overlapping fields A and B in a transformation series. These fields sharing one corner in Archostemata, Myxophaga, Rhysodidae, Trachypachidae and numerous Hydradephaga make me inclined to considering this character state as a plesiomorphy. This, however, is not certain because the fields overlap in some Gyrinidae and Dytiscidae, as well as in the Carabidae. Hence, this character is here recognized as a homoplasy of the families listed, yet a synapomorphy of some gyrinids (Dineutus, Porrorhynchus). The combination of cuj lying much proximal to the oblong cell and CuA geniculated at cuj is a characteristic feature of Gyrinidae and Myxophaga.

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When not so prominent, this character is also observed in Haliplidae, as well as Spanglerogyrus and, especially, certain big-sized gyrinids (Porrorhynchus). This implies that the character involved might have come out of the differences in body size at least in Gyrinidae. When regarded as a plesiomorphy, it enables to relate Gyrinidae with Myxophaga and, all things considered, place the Gyrinidae at the base of the Adephaga lineage. The opposite treatment invites two interpretations. Of them, the synapomorphy not only supports the monophyly of Myxophaga plus Gyrinidae (and also probably Haliplidae), but allows to directly derive Myxophaga from Gyrinidae. Not such a radical inference follows from the consideration of this character as a homoplasy of Myxophaga and some Adephaga resulting from the miniaturization trend. When longer, the section of CuA between cuj and the oblong cell (Gyrinus, Orectochilus) is combined with non-overlapping fields B and A, the field A being strongly to completely (most Myxophaga) reduced. As a working hypothesis, the latter of the above speculations invites this derived character to also be a homoplasy of Gyrinidae and Myxophaga. This similarity in evolutionary trends seems to be additional evidence to favour the rather close relationships between Myxophaga and Adephaga if not Gyrinidae. The structure of the articular area is highly specific, character transgressions being present therein as well. Derived characters appear to be as follows: longitudinally corrugated BM, med and cub, as well as the 1Ax posterobasal process strongly elongated and thus extending beyond PMNP of the alinotum (Brodsky, 1989). Contrary to this, feebly differentiated components of pmp+dmp, namely, the median plate more or less evenly sclerotized and weakly subdivided into BM, med and cub, seems to be the groundplan pattern. Interrelations of studied gyrinids are here defined as (Gyrinus + Orectochilus) + (Dineutus + Porrorhynchus). Haliplidae. The wing structural plan is less peculiar. Moreover, some features may have emerged from a miniature and compact body. The miniature body could have invited totally reduced 2a and ac, a strongly reduced 1a and also probably the rolled wing apex. The compact body seems to have led to the absence of a sub-cubital binding patch. A rather wide wing, with rml wider than mcl and the MP3+4 apex curved forward, makes Haliplidae similar to Dytiscoidea and Gyrinidae. The oblong cell closely resembles that of Spanglerogyrus in shape, and CuA geniculated at cuj which lies much proximal to the oblong cell adds to this similarity. Yet a long and lengthwise RP as the first distinction of the haliplid wing can be recognized as a groundplan feature of Caraboidea (= Geadephaga). Based on the above, the Haliplidae seems to be closer to Dytiscoidea or Gyrinidae rather than Caraboidea.

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Dytiscoidea. With few apomorphies left beyond the scope, the wing groundplan of Dytiscoidea is almost conformable to that of Adephaga. These apomorphies are a strongly shortened CuA2, a slightly shortened AP3b, neither CuP secondary base nor cu–a2 persisting, and a well-developed sub-cubital binding patch. The wing of Dytiscidae, Dytiscinae in particular, seems to be the least derived as combining separate apomorphies and numerous plesiomorphies, of which some are absent from the other Adephaga. These plesiomorphies are a polygonal cc, a modified but conspicuous m3 beginning on the rc posterobasal border, a long rms, a strong and vein-like primary base of CuP, and a rudimentary but distinct basal section of MA. The folding pattern is almost the same as that of Gyrinidae (Dineutus, Porrorhynchus) because of overlapping fields A and B, combined with a likewise folding wing apex. The other dytiscoids are farther advanced in wing structure in having a shortened rms, neither primary base of CuP nor the basal part of MA, nor m3, and cc of a derived shape. The Noteridae (Fig. A5) and the Amphizoidae (Fig. A6) better satisfy this character combination than the Hygrobiidae (Fig. A7) does. It is important, however, that the tendency towards these apomorphies taken separate or combined manifests itself also in Dytiscidae. A more or less rolled wing apex (apomorhy?), a long scw, a reduced axial cord, as well as 2a somewhat decreased in size deserve mention among the remaining characters of Noteridae as well. Except for Noterus, the noterids studied demonstrate a short and narrow cw, i.e. strongly to almost completely reduced. When running outside and close to fold bp, the RP+MA base is sure to be a derived pattern, too (Hydrocanthus, together with some Carabidae and laccophiline dytiscids). The Amphizoidae is conspicuous in showing subequally large, primarily long cw and scw. What these as well as some other characters are is obscured by the wing of Amphizoa being most likely unfunctional due to reduced wing muscles (Beutel, 1995). The absence of sbp from Hygrobiidae might have been a reversion coming out of a tubby body acquired. This follows from sbp having surely been lost also in some hydroporine dytiscids of a similar body shape. In general, the differences between Dytiscoidea1 and Caraboidea in wing structure are few. The dytiscoid wing is, on the average, wider, usually with rml broader than mcl; the oblong cell is always large, either cu–a2 or secondary base of CuP is absent, the m3 remnant is conspicuous in the groundplan; there are no traces of a forking AP4 because the axial cord either remains entire or vanishes stepwise into the wing membrane. Significant characters both the groups share are very few. 1

These differences could be attributed to all hydradephages but for the sub-cubital binding patch.

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These are chiefly plesiomorphies, among them: cc of a particular shape, as well as both the CuP primary base and the MA basal section persisting. A well-developed sub-cubital binding patch seems to be the only apotypic (synapotypic?) feature. Dytiscidae. No unambiguous synapomorphies have been found. Dytiscidae differ from Haliplidae and the other Dytiscoidea chiefly in the following derived venation patterns. Either RP and m1–MA are subequally long or a shortened RP is combined with R, the latter being very wide within cb and subdivided lengthwise into two parts, anterior and posterior. Using these characters, either Dytiscidae is subdivided into two lineages or, when the former character is a supposed homoplasy, the lineage Dytiscinae + (Colymbetinae + Agabinae) can only be defined. The Dytiscinae is considered a basal group in the lineage because the other dytiscids if not dytiscoids are of derived wing structure. Some groundplan characters could have evolved more or less independently in different dytiscines. Change in cc shape, the MA basal section reduced along with the CuP primary base and CuA2, as well as a modified and posterodistad shifted m3 seem to have been the immediate results of this evolution. A lacking or strongly shortened rsp is a synapomorphy of Agabinae and Colymbetinae which mainly differ from each other in the shape of the MP section between m1 and the oblong cell. This straight to feebly arcuate section is peculiar to Agabus and Ilybius, whereas the vein curved subrectangularly occurs in Colymbetes and Rhantus. Certain species of Agabus (A. undulatus, A. unguicularis) are distinguished from some others (A. sturmi) by a few characters which could be expected to have arisen from a generally despecialized wing venation due to the flight function in decline. These are a shortened apical membrane, a rather long RP, and R almost not broadened at the cb base. The wing of such a structure is only slightly different from that of Amphizoidae or Laccophilinae. Laccophilinae, Copelatinae and Hydroporinae are defined by a conspicuously longer RP (Goodliffe, 1939), combined with a not broadened apical section of R, as well as by the wing apex rolled (synapomorphy or, more likely, homoplasy); fields A and B overlapping (Hydroporinae) or not (Laccophilinae, Copelatinae). Copelatinae and Hydroporinae are more similar to each other, sharing RP as long as m1–MA and a narrow, long, L-shaped sclerotized strip inside cc (the “island”, according to Balfour-Browne, 1943), which is the tentative derivative of a rudimentary m2 (Figs A: 10, 11). Fused bases of free apical sections of CuA1 and MP3+4 seem to be an autapomorphy of Hydroporinae. A tendency towards a reduced 2a is intensified by the miniaturization trend, the combination of an originally great length and a lengthwise external border of the cell defining a particular way of this reduction. More specifically, as the cell grows proportionately smaller, it gets increasingly narrow (Hydrovatus) until the anterodistal and posterior borders of the cell meet (Hydroglyphus).

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A desclerotized base of CuA1 is a characteristic (synapotypic?) feature of Laccophilinae, to which a distinctly desclerotized (Laccophilus) to completely reduced (Neptosternus) RP and a truncated AAP can also be added. An anterodistad directed base of RP+MA is sure to be a derived pattern. A rather short RP drives Laccophilinae to the position between Dytiscinae + Agabinae and Laccophilinae + Hydroporinae. Thus, the Dytiscidae more or less naturally falls into three lineages: Dytiscinae + Colymbetinae + Agabinae, Laccophilinae, and Hydroporinae + Copelatinae. The interrelations between and within these lineages are definable in terms of cladistic dichotomy (Dytiscinae + (Colymbetinae + Agabinae) + (Laccophilinae + (Copelatinae + Hydroporinae). The variant Hydroporinae + (Copelatinae + (Laccophilinae + (Dytiscinae + (Colymbetinae + Agabinae)))) seems less probable. The great similarity between Copelatinae + Hydroporinae and Hygrobiidae in wing structure must not be overlooked. It is revealed based on numerous shared characters, among them: the rolled wing apex, the particular shapes of the wing, pst.c.–rc unit, cc, the remnant of m3 and the presence of a long sublinear m2. In addition, it is emphasized by sbp missing from Hygrobiidae and numerous hydroporines such as Hyphydrus, Hydrovatus, Stictotarsus or Hydroglyphus and also by a peculiar shape of CuA1. Hygrobia shows the base of this vein sharply curved and drawn closer to MP3+4, implying this pattern to have preceded both veins fused basally in hydroporine wings. The only essential difference between these dytiscoids is RP length. Carabidae. A unique combination of plesiomorphies and apomorphies is characteristic. Conspicuous cu–a2 (symplesiomorphy of Carabidae + Rhysodidae) and CuP secondary base, a traceable CuP primary base and a vein-like base of M distal to arc are important plesiomorphies. Particular shapes of pst, rc, 1a and 2a, a lengthwise RP, traces of the MA basal part and a long axial cord seem to be protofeatures as well. The reduced 2Ax arm (BR) (autapomorphy) and a very special folding pattern (autapomorphy of Carabidae + Trachypachidae) are important derived characters. A rather short AP3b and the rms shortened to totally reduced also deserve mention. The cross-vein m–cu4 which is longer than that of Hydradephaga or Archostemata is another characteristic feature1, albeit of dubious polarity. Plesiomorphies are scattered among various taxa of Carabinae s.l. = Carabinae s.str. + Elaphrinae s.l. (= Scaritinae s.l.) = Nebriiformes + Loxomeriformes + Melaeniformes sensu Erwin (1985). 1

This character, yet formulated otherwise, was used by Ward (1979) to support the subdivision of Adephaga into Carabidae (+ Rhysodidae) and Hydradephaga (+ Trachypachidae).

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Thus, the axial cord has persisted in all Carabinae, except for Apotomini, Paussitae, Melaenini and Pseudomorphinae. Higher grade carabids, Harpalinae s.l. = Psydriformes sensu Erwin (1985), have lost the cord (synapomorphy), this being barely traceable also in smaller Carabinae (e.g. Notiophilus, Miscodera) and Trachypachidae or reduced in small-sized Scarititae (Clivinini, Dyschiriini). The groundplan pattern of the structural unit composed of CuA and the oblong cell (Figs A: 14, 17, 18) is only found in Paussitae, Hiletini, Nebriitae (Opisthiini, Nebriini1, Notiophilini, Pelophilini, Notiokasiini (Kavanaugh, 1982, fig. 13)), Migadopini and Melaenini (Melaenus). A more or less entire cu–a2 occurs in Carabini, Opisthiini, Nebriini, Apotomini and Pseudomorphinae. The remaining ground beetles lack cu–a2 due to medially fused apical sections of CuP and AA1+2, their shared base varying from very long to indistinct (e.g. Notiokasis, Notiophilus, Patrobini, some Lebiini: Cymindoidea). A larger 2a with its distinct internal border is characteristic of most of Nebriitae. The cell of smaller size but, apparently, of less derived structure2 is observed in Hiletini, Omophronini, Cicindini, Carabitae (Carabini + Cicindelini), Loricerini and Pelophilini. This pattern is also to be considered as ancestral to Paussitae and Siagonini, both showing a reduced 2a following the 2nd pathway (see above) versus the 3rd one obviously used by the other carabids. Finally, the Carabitae has largely retained both the secondary base of CuP and RA conspicuous between pst and rc (Figs A: 19, 20). The other Carabidae can only retain traces of the CuP secondary base (Fig. A14). Its remnant, primarily as a short Cur, is more distinct in Opisthiini and Nebriini, but often found also in Harpalini (Harpalus, Dixus) and Brachinini. Hence, the wing groundplan of Carabidae seems to be closer chiefly to the wings of Nebriitae, Opisthiini and Nebriini, with Carabini showing slightly more derived ac and oblong cell, but less derived RP, CuP and 2a. The characters involved in the comparative morphological analysis at the family group level are mainly restricted to those discussed above. Most other characters are far less useful because of their stronger variability. Some of them, for example the length of CuP+AA1+2, are rather quantitative, so they are hardly arranged in transformation series. The same holds true also for the vein CuA1 distal to the oblong cell. In most cases (including Trachypachidae) it is long, lengthwise in the basal half and strongly curved backwards at its middle where a few folds 1

2

At least some Nebria (Fig. A15) show the oblong cell derived, cuneiform, whereas some other congeners (N. rufescens) display a more or less groundplan pattern (e.g. Fig. A14). The polarity of the variant shapes of 2a cannot be defined in distinct terms. The cell anterior border obviously shorter than the outer one is here hypothesized to be the groundplan pattern.

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usually converge (Figs A: 13, 14, 24–27). Alternatively, a short and nearly straight CuA1 of a more transverse orientation and the vein MP3+4 diverge just from their bases, without showing folds intersecting CuA1 (Hiletini, Paussitae, Omophronini: apomorphy?). Carabitae, some Cicindelitae (Cicindela) and Siagonitae (as well as Hydradephaga) display more or less intermediate patterns, which still seem to be closer to the latter of the alternative patterns, at least so morphologically. The structure of some other venational units such as ac–AP4 or pst–rc strongly depends on body size. It follows that the great similarity between bigand small-sized beetles in these characters could have resulted from size rather than phyletic evolution, especially miniaturization. Finally, anarc.c. is the most illustrative example of the patterns that vary considerably from genus to genus or even within some genera. This character seems to be appropriate for distinguishing between taxa hardly higher than tribal, often being of a very special pattern as defined by the combination of the total length of anarc.c., the length ratio of its anterior to posterior component, the distance from the wing base, etc. The following groups are well-separable using wing characters: (1) Harpalinae s.l. (= Psydriformes sensu Erwin, 1985, i.e. Trechinae (= Psydrinae) + Harpalinae s.str.). The wing groundplan comprises predominantly (syn)apotypic characters, as follows (Fig. A26): CuP+AA1+2 ranges between dot-like and (usually) long, 2a is subjected to the 3rd pathway of reduction, either a narrow triangle or absent, rarely with a more or less indistinct internal border; ac is completely reduced; the oblong cell varies from cuneal to reduced; the pterostigma is complex (pst.c.). Intragroup differences are the least, being often comparable with those induced by variation in body size. Body miniaturization brings about or accelerates the following main transformations of the groundplan: the oblong cell, 2a, AA1+2 and the CuA1 basal part reduced, as well as pst.c. desclerotized anteroapically (Clivinini, Dyschiriini), with a conspicuous excavation (Trechini) substituting for this membranous area afterwards. (2) Carabinae s.l. (Carabinae + Elaphrinae = Nebriformes + Loxomeriformes + Melaeniformes, sensu Erwin, 1985). This wing type is specific due to a combination of polythetic, mostly plesiomorphic characters. Among them, either a well-developed ac or a conspicuous cu–a2, combined with the oblong cell and 2a of primitive shapes, is the most important. Elaphrini, Scaritini and Broscini retain only ac among the groundplan features, thus being advanced farthest in the lineage. Omophronini and Loricerini seem to be not too derived in showing 2a of groundplan structure while Hiletini and Pelophilini still less so (+ the oblong cell of primary shape). Carabitae and Cicindelitae mainly share wing plesiomorphies. These are primarily a short and wide 2a, as well as a long and loop-shaped ac–AP4 association

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(Figs A: 19–21) which is detached from the wing margin in addition. Both the latter character and a wedgy or absent oblong cell seem rather to be synapomorphies. The folding patterns of higher complexity shared by Carabitae and some Cicindelitae (Cicindela) imply homoplasy because at least certain tiger-beetles (e.g. Neocollyris) show the folding pattern typical of the Carabidae. Derived features of cicindelite wings are certain to be AA1+2 shifted onto CuP, a reduced oblong cell, as well as the pst–rc unit of a particular structure and the fold sc convex in some representatives. These characters and probably also a very long rms appear to be morphological adaptations to improve wing flight or folding qualities, or both. When interpreted as an apomorphy, the ac–AP4 association loop-shaped and distant from the wing margin enables to relate Carabitae + Cicindelitae to Cicindini (Kavanaugh & Erwin, 1991, fig. 16) or Siagonitae. Siagona (Fig. A22) is peculiar due to the wing apex non-folding transversely, with either 2a or cu–a2 absent. Because the latter pattern has resulted from the combination of 2a reduced following the 2nd pathway and a desclerotized cu–a2, the Siagonitae has no other close relatives but Carabitae. The closer relationship of both is also supported by some other imaginal characters, those of abdominal terminal segments in particular (Deuve, 1993). The wing type of Carabini is really conformable to the carabite groundplan and poorly different from that of Nebriitae. The latter is characterized by the primary shape of the oblong cell, combined with 2a somewhat enlarged but constricted basally due to its anterior border elongated and the internal border shortened (synapomorphy). The wings of Opisthiini, Nebria (primitively) and Leistus fit in well with the above groundplan, whereas those of Notiokasiini and Notiophilini are more derived, since cu–a2 is reduced. Pelophila is more peculiar because a missing cu–a2 is coupled with 2a of primary shape, the pattern very closely resembling that of primitive Elaphrinae, especially Hiletini (Fig. A18). The Paussitae shows the wing type which is readily derivable from the hiletine one through reduced ac and 2a (following the 2nd pathway) (Fig. A17). The Melaenini is about the same (ac reduced, together with 2a beginning to reduce following the 3rd pathway), as well as the other Elaphrinae (2a showing the 3rd pathway of reduction, plus a partially to completely reduced oblong cell). The Hiletini, Paussitae and Melaenini also share a fairly short and straight CuA1 (synapomorphy?). Among the traditionally incertae sedis groups, the Brachinitae is very similar to the Harpalinae, certain brachinites (Pheropsophus) sharing a tendency towards a shorter internal border of the oblong cell with Melaenini. Both Apotomini and Pseudomorphinae (Sphallomorpha) are advanced in almost all wing characters. Yet a well-developed cu–a2 taken separate (Apotomus) or combined with a rather long rms remnant (Sphallomorpha) implies that both groups are earlier derivatives of Carabinae.

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Rhysodidae. The combination of a few conspicuous plesiomorphies and a considerable number of apomorphies is characteristic. Among the plesiomorphies is surely the cb structure typical of Adephaga, combined with well-developed 2Ax arm (BR) and cu–a2. Synapomorphies are the following lost structures: the primary and secondary bases of CuP, the oblong cell, the anal cells, the anarc.c., the basal section of RP+MA, the ac and the AP3 base. These are also added to a single longitudinal vein in the clavus, a small jugal lobe with a rudimentary AP4, an evenly sclerotized pst.c., a straight anterodistal border of cc, and no veins inside cc. A fairly long but not vein-like rms can be referred to as a plesiomorphy. The sclerotized patch adjoining the posterodistal border of pst.c. suggests it could have been a rudimentary RP1+2 strongly curved at its base in the groundplan. Be the rhysodid cubital spur homologuous to CuA2, the Rhysodidae could be considered as nothing else but the basalmost group of Adephaga, as Crowson (1955) believed. Yet no traces of CuA1 persisting in front of the spur suggest that it is CuA1 that is a direct extension of CuA. If true, the Rhysodidae and the Carabidae have to share a distinct cu–a2 (symplesiomorphy), as well as two underlying synapomorphies, i.e. tendencies uncharacteristic of the other Adephaga, those towards (1) a reduced oblong cell and (2) the CuA1 base shifted caudad through m–cu4 being “elongated” (cf. Figs A12 and A21). Based on this, the highly peculiar folding pattern of the rhysodid wing apex is to be recognized as an autapomorphy of the Rhysodidae while the shapes of cc and rc–pst.c. as rhysodid synapomorphies and homoplasies of Rhysodidae and some Hydradephaga. In any event, the entire 2Ax versus 2Ax lacking the arm (BR) (carabid autapomorhy) allows the Rhysodidae to be considered as the sister to Carabidae (Crowson, 1960) or Carabidae + Trachypachidae at best, not a member of Carabidae, either a supertribe of Psydriformes (Erwin, 1985, 1991) or a tribe or subtribe of Scarititae (Bell & Bell, 1962; Bell, 1998). Trachypachidae. Only the entire 2Ax, a little more distinct remnants of m3 and m2, as well as a slightly longer AP3b are among plesiomorphies absent from the carabid wing. The list of apomorphies, on the contrary, is much larger: neither CuP primary or secondary base nor cu–a2, nor 2a, nor the distal section of the RP+MA base; a fairly short ac–AP4 association; all of these synapomorphies are reductionist, probably resulting from a rather small body size of extant Trachypachidae. Based on this, Trachypachidae and Carabidae do not seem to differ from each other in wing structure, small details included, while both sharply contrast with the rest of Adephaga. This prevents me from questioning sister-group relations of Trachypachidae and Carabidae and at the same time inclines to hypothesize the sub-cubital binding patch to have been a synapomorphy not only of Dytiscoidea + Trachypachidae (Ward, 1979; Beutel, 1995), but Carabidae and probably also Rhysodidae. The lack of sbp thus has

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to be recognized as a homoplasy of Hygrobiidae, some Dytiscidae, Systolosoma, Carabidae and Rhysodidae. Yet parallel developments of sbp in Trachypachus and dytiscoids do not seem unlikely as well. To summarize, one should conclude that Adephaga falls into Gyrinidae, Haliplidae, Dytiscoidea, and Caraboidea (= Geadephaga). The relationships between these taxa have not been resolved by comparing their wing groundplans, since these are of one and the same morphofunctional type. Similar results, because of a considerable character transgression, have come out of analyzing these groundplans reduced to independent characters. Only with selected characters involved in analysis, answers to the problem have become restricted to a few, often alternative solutions. More specifically, the Adephaga can be subdivided into the traditional groups Geadephaga and Hydradephaga on the basis of such a couplet as present/absent cu–a2, respectively; these groups are also distinctive in wing shape and some venational, perhaps shape-related characters. However, that numerous Coleoptera realize the tendency towards a reduced cu–a2 in parallel strongly lighten the phylogenetic weight of this character. This means here that CuP+AA1+2 could have also been developed in parallel in Gyrinidae and Haliplidae + Dytiscoidea, hardly all of the hydradephagan families. Were it true, nothing but one among a few possible interpretations of the veinal bridge between CuP+AA1+2 and AA3–AAP in gyrinid wings would prevent sister-group relationships between Gyrinidae and the remaining Adephaga. Nevertheless, I am inclined to follow the scheme Gyrinidae + ((Haliplidae + Dytiscoidea) + Caraboidea) which agrees with the results of comparative morphological (Beutel & Haas, 1996) rather than molecular studies (Ribera et al., 2002), still not denying the existence of the monophyletic groups Hydradephaga and Geadephaga. As regards the Dytiscoidea, I am only to state they are scarcely distinguishable by wing characters. Dytiscinae + Agabinae + Colymbetinae and Hydroporinae are clear-cut lineages within Dytiscidae. Sister-group relations between Carabidae and Trachypachidae are also confirmed while the Rhysodidae is excluded from Carabidae.

Staphyliniformia The monophyly of Staphyliniformia s.l. is supported by a particular wing groundplan which integrates the following principal synapomorphies: (1) aj present, (2) cas/pstII well-developed, (3) fold hw intersecting the CuA2 base, (4) one apical branch reduced in clavus, (5) membrane crimping well-developed. Realizations of a few shared evolutionary tendencies is to be added to this

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character set, among them a reduced rc, differentiation of branches of membrane crimping, with some of them transformed into secondary veins, and the development of a “simplified” fan-folding accompanied by oligomerized supporting axial elements. A weak and shortened to lacking CuA2 is likely to be a synapomorphy as well, whereas MP3+4 substituted for CuA2 is not so evident and only supposed for Sphaeritidae, Synteliidae and Scarabaeidae. A lacking sbp probably also deserves mention among symplesiomorphies. Let me note once again that wing types, especially venational ones, of hydrophiloid families (Helophoridae, Hydrochidae, Georissidae, etc.) are very close both to one another and the superfamily groundplan. Wing characters suggest that Sphaeridiinae could be a stem-group for histeroids and even the Scarabaeoidea. Venational characters of the anal region (either AP3a or AA3b+(AA4+AP1+2) reduced) argue in favour of assessing histeroid relationships as Sphaeritidae + (Synteliidae + Histeridae) (Caterino & Vogler, 2002; Beutel & Leschen, 2005: a cladogram based on larval characters) rather than Synteliidae + (Sphaeritidae + Histeridae) (Beutel & Leschen, 2005; Caterino et al., 2005). Moreover, Sphaeritidae and Synteliidae + Histeridae are not unlikely to have descended from close but different hydrophilid ancestors. Saprininae are appreciably less derived than Histerinae in wing structure and could have been a link between Sphaeridiinae and Histerinae. The Scarabaeoidea very closely resembles the Hydrophiloidea, especially Sphaeridiinae. The peculiarities of Scarabaeoidea are restricted to only a few synapomorphies, among them a partly reduced cub, MP3+4 substituted for CuA2 and a somewhat modified folding pattern. Both superfamilies also share a tendency towards reduced AA3a' and one of the two posterior veins in the clavus. The differences between Hydrophiloidea s.l. + Scarabaeoidea and Staphylinoidea look more prominent chiefly due to two characters. In particular, the latter lineage is defined by the combination of the apical joint of a more primitive structure and a better developed pstII (synapomorphy), and vice versa. The results obtained agree with Hansen’s (1995, 1997) conclusions on sister-group relations of Scarabaeoidea and Hydrophiloidea + Histeroidea. Moreover, it seems quite probable that histeroids and scarabaeoids have emerged from different but close hydrophilid ancestors. Two lineages, lucanid and scarabaeid ones, are well-traceable within Recent Scarabaeoidea, each defined by a reduced particular anal vein (see above). Besides this, representatives of the former lineage share mainly the wing plesiomorphies that concern the sclerotization pattern and the venation of the clavus. Either Trogidae + Lucanidae or Bolboceratidae have to be selected as a stem-group, the Bolboceratidae in general retaining the least derived venation of the clavus (AA3a' barely separated from AA1+2) and probably also the primary sclerotization pattern of the apical membrane.

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Members of the scarabaeid lineage also share such apomorphies as a welldeveloped abs and the AA3a' either lying close to AAP or reduced. The wings of the most generalized structure are observed in Hybosoridae, as they combine these or those characters shared by many other representatives of the lineage. In particular, hybosorids seem to be intermediate between Anoplotrupes, Passalidae and Ochodaeidae, on the one hand, and Pleurostici (Figs A: 53, 56), on the other, in shape of the central sclerotization of the apical membrane (U- or S-shaped pattern), the mas–aas patch varying from arched to rectangular (Figs A: 48, 49–55–56–50, 53, 57, 58). Such characters as SV2 forked (Pleurostici, Passalidae, most of Hybosoridae) or non-forked (Ceratocanthidae, Scarabaeidae Laparostici) into cab and aas basally are linked together by transitions (Fig. A50, plesiomorphy, – A48 – A55). The combination of inflated bases of AA4–AP1+2 and AP4 (Fig. A55) is also attributable to most of Scarabaeidae. A finely and sparsely serrate costal margin on both sides of aj can be a synapomorphy of Hybosoridae and Anoplotrupes. Ultimately, the folding pattern (Fig A55) of the hybosorid wing most closely resembles that of Scarabaeidae Pleurostici. Given this and at least the Upper Jurassic age of Hybosoridae (Krell, 2006), that group could claim the status of being basal in the lineage involved. Yet Geotrupidae or Ochodaeidae seem better fits. The geotrupid wing is almost undistinguishable from the bolboceratid one in the sclerotization pattern of the apical membrane (SV2, aas + entire pcas, etc.) while bearing the rc of a derived structure. In contrast, Ochodaeidae show rc of a primitive shape and the sclerotization pattern which integrates both plesiomorphies (SV2 wide but not vein-like, SV3 developed) and apomorphies (SV2 separated both from cab and the pcas basal part, latter being wide and triangular). This is hardly surprising, for Geotrupidae and Ochodaeidae are considered as close both to each other and Hybosoridae in recent cladistic reconstructions (Browne & Scholtz, 1996, 1999; Krell, 2006). Passalidae (Fig. A49). The wing is of very special structure. The combination of a U-shaped sclerotization pattern of the apical membrane, AA1+2 lying closer to CuA than to AAP, especially so at base, a strong cas extended to the wing apex, a doubled MP3+4 and a reduced AP3a, all this makes me inclined to treat Passalidae either as the basal group in the scarabaeid lineage or an early derivative of Geotrupidae. When well-developed in Aulacocyclinae (Ceracupes), vein AA3a' is nevertheless subequally distant from AA1+2 and AAP, thus approaching the pattern characteristic of the lucanid lineage, Lucanidae in particular (Fig. A45). In spite of this, the close relationship if any between Passalidae and the lucanid lineage seems less likely. Ceratocanthidae (Fig. A51). This family appears to be closer to Ochodaeidae, for both share (1) a similar folding pattern, (2) a rather short cas which is distant from the wing costal margin, (3) a fairly short rc, (4) aas either absent or, if weak, then separated from SV2, and (5) cab either absent or not adjoining

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the SV2 base. This conclusion is ambiguous because the polarity of the listed characters is not clear-cut. Proceeding only from the assumption that most of the above characters are derived, Ceratocanthidae could have descended from Hybosoridae, some of whose members (e.g. Phaeochroops) also show the tendency towards a reduced vein AA3a'. Glaresidae (Fig. A52). The character combination is distinctive. A large rc, the outline of the sclerotization pattern of the apical membrane, especially SV2 reaching field D, and the anals contiguous at the clavus base draw Glaresidae closer to Ceratocanthidae. On the other hand, a wanting abs and the subcostal bulge bearing a row of strong setae might be synapomorphies of Glaresidae and Trogidae. However, a particular venation of the clavus seems to be an obstacle to this hypothesis. In the opposite case, a lacking abs is to be considered as probably resulting from its reduction or perhaps depigmentation consequent upon a general weakness of the sclerotization pattern. Glaphyridae (Fig. A53). All of the following wing characters point to a closer relationship between Glaphyridae and Scarabaeidae: only a single strong separate vein (AA1+2) between CuA and AAP, a reduced 2Ax arm (BR) and the S-shaped central sclerotization of the apical membrane (this is quite separate in Scarabaeidae, but fused to the sclerotization skirting rc in Glaphyidae). The only glaphyrid autapomorphy is cab–SV4 substituted for SV2, but similar patterns also occur in Scarabaeinae (Scarabaeus), less so in Geotrupidae (Fig. A48). In placing Cretochodaeus mongolicus Nikolajev, 1995, from the Lower Cretaceous, I follow Krell (2006) who has considered it a glaphyrid, not ochodaeid, as originally stated. Scarabaeidae (Figs A56–62) are not or only poorly different from Hybosoridae in wing groundplan: both groups share a similar sclerotization pattern and two separate veins, AA1+2 and AA3a', in the clavus. But aside from relicts showing both these veins developed (Phaenognatha, Aclopinae: Kukalová-Peck & Lawrence, 1993, fig. 53), most of the Scarabaeidae retain AA1+2 alone, this being somewhat angulate at its short base and approaching AAP apically. Besides this, Scarabaeidae (all?) share a reduced 2Ax arm. The tendency towards an enlarged AP1+2 base is also characteristic. Sericini (Fig. A56) or, because of mch not broadened apicad (plesiomorphy), Hopliinae seem to be of the least advanced wing structure, including a strongly angulate posterior border of 1a. Yet the latter character could partly be derived, since an angulate rather than strongly angulate posterior border seems to be a plesiomorphy. If so, this character could support the monophyly of Sericini + Hopliinae. The wings of the remaining Pleurostici studied (Euchirinae, Melolonthinae, Dynastinae, Rutelinae) share at least two derived characters. An apically broadened mch is the first while the second is revealed as a tendency towards a

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smoothed angulate curve of the 1a posterior border, Laparostici showing this tendency as well. The Euchirinae among the four subfamilies listed seems to be closer to Rutelinae or, more likely, the most primitive and annectent between Sericini–Hopliinae and Melolonthinae–Rutelinae. Cetoniinae are much farther advanced in having mch subequally narrow throughout its length (tentative synapomorphy, derived from an apically broadened mch). Trichiini (Fig. A58), especially Gnorimus, are closer to Cetoniinae in wing groundplan while Cetoniini and Valgini are less so. C–(C+ScA) desclerotized ventrally and tuberculate conspicuously but sparsely over its ventral or anteroventral margin can be a synapomorphy of Cetoniinae and Rutelinae. In these two families, the sclerotization patterns of the apical membrane are also similar both in general and in the constituent parts such as cas, pcas, aas, cab and SV2. Among them, a homogeneous and fairly weak patch composed of fused pcas, aas and cab is especially prominent. Laparostici show a strongly different wing type. It is predominantly defined by apotypic characters. Among them, the least variable are as follows: cb of a particular structure, a strengthened RMP base and the sclerotization pattern of the apical membrane reduced to the strip cs–abs, the latter being sublinear to Г-shaped and perpendicular to RMP. This character combination requires to be supplemented by MP3+4 intersected by fold gu, coupled with the sclerotization pattern composed of SV2b strengthened at its base, pcas strongly reduced in size and cab reduced, but sometimes either persisting as traces (Sisyphus) or reverted (Scarabaeus). Only such characters as pstII membranous along the costal margin, AA3a' survived as a weakly sclerotized strip and the posterior border of 1a sharply or smoothly angulate (Aphodiinae; Oniticellus, Onthophagus) can be referred to as plesiomorphies. Aphodiinae s.l. are generally a little more primitive, showing a straight cubital spur (MP3+4) and icsp neither strengthened nor extended to the wing margin. There are no other modifications in secondary veins, but SV2 split into SV2b and SV2b. The Scarabaeinae is more derived and also much more variable. The principal wing synapomorphies are as follows: an S-shaped MP3+4; icsp strong, long, often reduced basally (Oniticellus, Onthophagus, Sisyphus); a V-shaped strip composed of MP3+4 and icsp; presence of additional secondary veins caudal to SV2b. The strip SV2 varies from entire (Oniticellus) to split either basally (Scarabaeus, Onthophagus) or all along (Copris, Sisyphus). The results obtained could be arranged into the following dichotomies: ((Lucanidae + Trogidae) + Bolboceratidae) + ((Geotrupidae + Passalidae) + ((Ochodaeidae + Ceratocanthidae + Glaresidae) + (Hybosoridae + (Glaphyridae + Scarabaeidae)))) for Scarabaeoidea, and (Aphodiinae + Scarabaeinae) + (Hopliinae + (Sericinae + Melolonthinae + Dynastinae + (Rutelinae + Cetoniinae))) for Scarabaeidae. Both reflect group similarities/differences in wing

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characters of mainly two transformation series, those for the sclerotization pattern of the apical membrane and the anal branches in the clavus. A phylogenetic interpretation of these schemes argues for (1) an early divergence of the lucanid and scarabaeid lineages, (2) close interrelationships of Bolboceratidae and Geotrupidae, and (3) the origin of Glaphyridae + Scarabaeidae from near Hybosoridae or directly from a hybosorid. Either can be reinterpreted following changes in the polarity of the characters involved in analysis. Staphylinoidea more or less naturally fall into the agyrtid lineage (Agyrtidae, Colonidae, Leiodidae, Hydraenidae, Ptiliidae) and the staphylinid one (Silphidae and Staphylinidae, including Pselaphidae, Scaphidiidae, etc.). The Scydmaenidae shares all of the wing synapomorphies with the former lineage, being especially close to Leiodes, Leiodididae, including such plesiomorphies as a traceable CuA2. However, a rudimentary but traceable aj has survived in Scydmaenidae, implying this family could have been annectent between both of the lineages. Silphidae seem to be extremely similar in wing structure to Staphylinidae, especially Omaliinae. The latter similarity is largely supported by the entire pstII supplied with a small caudal process probably homologous to aas (a much more prominent process is also peculiar to Agyrtidae, Fig. A63). Silphine wings are less derived than those of Nicrophorinae: cb is fairly long and not desclerotized, the membranous costal flap is short and disappearing far proximal to aj, pstII is entire, with a small but sharp caudal process at the middle; there are distinct cu2, AA1+2+AA3a' base and the apical part of AA3a'. Except for distinct remnants both of the AP3 and AP3a bases (which could be so prominent for secondary reasons), nicrophorine wings are characterized by the following apomorphies: a strongly shortened cb, the costal margin desclerotized all along, the membranous costal flap as a narrow lobe extending beyond aj, pstII smoothed along its posterior margin, both cu2 and the AA3a' apex reduced, the jugal lobe strongly extended anterobasad, secondary sclerotized strips more strongly developed on each side of CuA2. Hence, the relationships within Staphylinoidea seem to be better interpreted either (Silphidae + Staphylinidae) + Scydmaenidae + agyrtid lineage or (Silphidae + Staphylinidae) + (Scydmaenidae + agyrtid lineage), or even (Silphidae + Staphylinidae) + ((Scydmaenidae + Leiodidae) + the remaining families of the agyrtid lineage).

Elateriformia As it follows from a comparison between the wing groundplans reconstructed here for all of the elateriform superfamilies, the morphological gap between Elateroidea and Byrrhoidea is much narrower than between each of them and

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Buprestoidea plus Dascilloidea (hereinafter Buprestoidea s.l.). The differences between the former two taxa are almost negligible in folding patterns and hardly stronger in the sclerotization patterns and wing venation. Based on these characters, the following two phylogenies of Elateriformia could be put forth. According to the first evolutionary scenario, a comparatively simple “diversicorn” folding pattern was the groundplan. Proceeding from this assumption, the elateriform ancestor could have been a byrrhoid close to laraine elmids or Callirhipidae. Thence, Eulichadidae are to be recognized as close to the ancestor both of Elateroidea and Buprestoidea s.l., with the reservation that this hypothetic ancestor had developed the elaterid folding pattern, but retained the complete venation in the clavus before Elateroidea plus Buprestoidea s.l. diverged. The second phylogeny which I prefer implies that primitive elateroids, Artematopodidae first of all, could have been at the base of the elateriform stock, with Byrrhoidea + Buprestoidea s.l. emerging thereof. These are characterized by a different ratio between cw and scw, together with a secondarily simplified folding pattern, except in Eulichadidae. Fundamental differences between Byrrhoidea and Buprestoidea s.l. in the folding pattern make it possible to treat these groups as sisters, regarding AA1+2 shifted onto CuP as a homoplasy. Elateroidea. What fits in best with the wing groundplan of Elateroidea is only the wing of Artematopodidae (Fig. A70). The latter family embodies many plesiomorphies, chiefly including the true field B, combined with a short field C, occurring in no other elateriform beetles but Dascilloidea. The remaining plesiomorphies are as follows: a distinct internal border of cc, the elaterid folding pattern, a short and wide rc, an unclosed field D, a well-developed Cur, as well as both long cu–a2 (Electribius: Lawrence, 1995) and Mr. However, the rc outer border is already unbent and the sclerotization pattern of the apical membrane is very weak (Macropogon) while the external border of 2a is sometimes absent (apomorphies). The former two characters may have resulted from the rolled wing apex. At the next evolutionary stage, field C appears to have extended a little basad, thus penetrating inside rml and resulting both in field B' substituted for B and a more or less strongly desclerotized border between rml and cc. Given the character transgression, this groundplan underlay the wings of the other elateroids, being especially close to those of Brachypsectridae, Cerophytidae (Fig. A71) and some Elateridae (Figs A77–78). Apomorphies of special groups are either a closed field D (Brachypsectridae) or an unbent outer border of rc, together with a reduced external border of 2a (Brachypsectridae, Cerophytidae), or a modified, including posteriorly reduced, sclerotization pattern of the apical membrane, combined with Cur, as well as fields Ia and Ip obliterated (Cerophytidae). Cerophytidae resemble Eucnemidae in a few wing characters, the latter generally being farther advanced. Both share a strengthened aas–pcas, as well

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as “r–m” longer than the mch section between “r–m” and the CuA2 base. The latter character, together with a conspicuous abs, can be a homoplasy while cu2 transformed into a new base of CuP and a reduced 2a (because of AA1+2+AA3a merged into AAP) are sure to be such. The ScP base directed more transversely than in most of the other elateroids (or, in other words, the entire cw lying distal to scw) is another derived character defining Cerophytidae, Eucnemidae and at least some Throscidae (Figs A: 71–74, 76). Wings of various Eucnemidae belong to a particular wing type due to the combination of polythetic characters, with two principal synapomorphies in support: AA1+2 shifted onto CuP and the field C extended to the wing base1. A posterodistad oblique r1 and a more or less strongly shortened to missing “Rr” define Phyllocerinae and the rest of Eucnemidae, Perothopinae excluded. Except for Phyllocerinae and Perothopinae, Eucnemidae share cu2 transformed into the CuP base, a well-developed abs and a tendency towards a reduced 2a. The wing of Throscidae fits in well with the wing groundplan of Eucnemidae, except for Phyllocerinae and Perothopinae, supplemented by the apomorphies some eucnemids tend to develop, an obliterated CuP and prs strongly elongated and broadened apicad (Fig. A74) being among them. Moreover, certain members of both families show such a profound similarity in wing structure that Throscidae could even be considered as not only the sister to but a derivative of Eucnemidae. When in the groundplan, the wing of “cantharoid” families differs from that of Elateroidea but Artematopodidae by a slightly modified sclerotization pattern of the apical membrane, a (sometimes incompletely) reduced Cur, a posterodistad directed r1 and the field C extended to the wing base. The latter three characters are also synapomorphies of at least some Eucnemidae and Throscidae. The similarity between these two families and “cantharoids” becomes apparent from a comparison between the wings of an advanced structure, i.e. with field S and, consequently, sclerotization cs enlarged due to fields Ia and Ip reduced. Omalisidae and probably also Drilidae can be recognized as the most primitive members of the “cantharoid” lineage, since they have retained the basic, i.e. elaterid, folding pattern. That the cantharid folding pattern (autapomorphy) is derivable from nowhere else but the elaterid one indicates the Cantharidae to be an earlier derivative of the lineage. A reduced cu–a2, combined with an apically open 2a, argues in favour of a derived wing venation of Cantharidae. The 1

The latter character is here tentatively attributed to the wings of Perothopidae I have only seen depicted. Whether the folding patterns of these wings are of the elaterid type, as is in Phyllocerinae, or of the “diversicorn” type, as is in most of the other Eucnemidae, remains uncertain.

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monophyly of the remaining “cantharoids” or at least Lycidae, Lampyridae and Omethidae is supported by the presence of the “diversicorn” folding pattern, namely, the field association C–S–D they share (synapomorphy). In many higher taxa of the Elateridae, intragroup and intergroup differences in wing structure are comparable, some members known to be remote allies, e.g. Hemiopinae (Hemiops) and Elaterinae (Chiagosnius), often being almost identical. This suggests either an early explosive diversification of Elateridae or a highly stable groundplan of the elaterid wing, or both. Some way or other, this groundplan proved to be shared nearly unmodified by not only different elaterid groups, but also numerous representatives of these groups. Almost all of the derived characters were either reductions (e.g. of Cur, cu–a2, the 2a external border, the CuP distal section, these or those sclerotizations) or resultant from these reductions (e.g. 1a and 2a separated due to a reduced AA3b). These, as well as some other venational characters or patterns concerning the shape of rc, the orientation of r3, the topology of particular veins, etc., occur in various groups of Elateroidea, implying their frequent parallel developments, including those in the course of size evolution. All these facts in toto are weighty grounds to interpreting many of the derived characters, character combinations and even certain wing types as homoplasies, i.e. characters of lightened taxonomic and, especially, phylogenetic weight. Based on this, I almost fail in drawing any sharp distinction between the results of anagenetic and phyletic evolution using available material. Only Agrypninae seem to be reliably definable by wing characters (Figs A79–82). This is first due to a highly stable venation pattern in the clavus, namely, the combination of two synapomorphies, an apically open 2a and the AA1+2 shifted onto CuP. A more or less well-developed aas' adds specificity to the wing, the absence of this character from some agrypnines, e.g. Danosoma, Tetrigus or Anthracalaus, making it possible to alternatively arrange this transformation series. Among the wings studied, including these depicted by Dolin (1975, 2000), Calder (1990) and Kukálova-Peck & Lawrence (1993), those of Tetrigus, Hemirhipini, and Anthracalaus, Pseudomelanactini, strongly resemble each other (a posterodistad oblique r1, the aas–pcas almost straight and not reaching the wing apex, an absent aas'). Danosoma shows a similar condition, but r1 is directed posterobasad. Cryptalaus (Hemirhipini, Fig. A81) and Chalcolepidius are not different from each other at least in venational characters. A somewhat modified aas', combined with aas–pcas arched forward, implies that some other Agrypninae (Figs A: 79, 80) are closer allied to the latter two genera and still more so to Conoderini in sharing the sclerotization pattern of the apical membrane reduced from three-branched to being composed of only two lateral branches, aas and MP3+4. Both Tetralobus and Pseudotetralobus, Tetralobini, differ from Agrypninae, especially some Hemirhipini (Fig. A81), in nothing else but

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an allometrically changed venation of the wing basal part. This suggests that the Tetralobini is a strongly specialized derivative of the Agrypninae (Stibick, 1979; Calder, 1990) rather than a separate subfamily of itself (Laurent, 1967; Calder et. al., 1993; Lawrence & Newton, 1995). Cardiophorinae and Negastriinae share similar (analogous or homologous?) venation of the clavus and sclerotization pattern of the apical membrane with Agrypninae, the latter pattern being represented by the “trident” reduced to MP3+4 and the aas–pcas separated basally, with aas–pcas desclerotized apically and extended into aas' anteriorly. As to the clavus venation, this also holds true for Penia, Dendrometrinae, whereas the other wing characters point out this beetle as being one of the most primitive elaterids. However, this primitiveness can be applied to the remaining Dendrometrinae, too. It is revealed in many characters such as a short field C, the complete venation of the clavus and AA1+2 situated distal to AA3a". A synapomorphy of the bulk of the Dendrometrinae is the three-branched sclerotization pattern of the apical membrane reduced to aas–pcas alone. Another synapotypic character is a tendency towards separation between 1a and 2a through AA3b reduction. In addition, numerous Dendrometrinae show highly unstable patterns both of the clavus venation and field group D–S–Ia–Ip to complete the above characteristic. Whether this instability is primary or secondary, remains uncertain. Virtually all of the wing features of Negastriinae such as a missing 2a, an apically broadened cb, a short rc, a long apical membrane and a distinct jugal incision (Dolin, 1975) say almost nothing but these beetles being small to very small. Most of the other elaterid subfamilies are hardly distinguishable from one another in wing groundplan if at all. This is chiefly due to the entire venation of the clavus and the sclerotization pattern of the apical membrane (“trident”), Elaterinae (Dicrepidiini, Melanotini and Elaterina), Eudicronichinae (Eudicronychus, Anisomerus) and Hemiopinae (Hemiops) being the best illustrations. Pitiobiinae, Oxynopterinae, Semiotinae and Cebrioninae are scarcely different from them in showing the “trident” partly reduced. In particular, Oxynopterinae and Semiotinae are more similar to each other than to the remainder while Oistus is more similar to Oxynopterinae than to Semiotus. Lissomine wings of a primitive structure, Austrelater taken as example, closely resemble those of Elaterinae. To summarize, the genealogy of the Elateroidea as here reconstructed assumes the following. The Artematopodidae is sure to be the stem-group, with Brachypsectridae, Cerophytidae and Elateridae being derived. The “cantharoid” lineage could have emerged from near any of the latter three. The interrelationships between “cantharoid” families seem to be better defined as Drilidae + Omalisidae + (Lycidae + Omethidae + Lampyridae) + Cantharidae. Eucnemidae + Throscidae appears to be the sister to Cerophytidae or Lissominae.

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Byrrhoidea. An answer the question how byrrhoids interrelate depends on which family groundplan is to be recognized as the closest to that of the superfamily. Either Eulichadidae or Callirhipidae, or Larainae, Elmidae, pretend to this status. Apomorphies are only restricted to a missing cu–a2 in the former two taxa as against the “dryopiform” folding pattern, combined with an apically reduced MP3+4 situated close to CuA2, in the latter. Each of the three families is defined by a particular folding pattern, either elaterid or byrrhoid, or “dryopiform”, respectively. Because it is this succession that is followed in the transformation series, I select the Eulichadidae as a stem-group. Proceeding from this assumption, the Byrrhoidea naturally falls into two lineages, the psephenid (or byrrhoid proper) and dryopid ones, each chiefly defined by interdependent characters of the field D and the sclerotization pattern of the apical membrane. In the psephenid lineage (Eulichadidae, Callirhipidae, Ptilodactylidae, Chelonariidae, Psephenidae, Byrrhidae), aas–aas' remained lengthwise because of an originally longitudinal and narrow field D, with a wanting abs and a strongly to completely reduced pcas (Figs A93–97). The aas–aas' strip got reinforced, pcas being either fused to it throughout but apically (Eulichadidae) or merged into the wing membrane (the other families). The radial cell of primary shape persisted only in Eulichadidae and Callirhipidae. In the remaining groups, rc gathered a particular shape from r1 getting oblique posterobasad and thence running subparallel to (RP1+2+r2)–r2 in the form of the outer cell border. MP3+4 was first drawn closer to CuA2 (Eulichadidae) and then reduced. Conversely, in the dryopid lineage (Elmidae, Dryopidae, Heteroceridae and Limnichidae) the field D became transverse and broader posteriorly (Figs A: 98, 99), thus pushing the base of a V-shaped aas'–aas–pcas pattern distad, with its branches aas–aas' and pcas more strongly divergent. The former branch grew transverse while the latter either remained entire or was interrupted where intersected by the fold e2. The radial cell under the influence of field B (this mostly degenerated into a fold) and one to a few weak, newly formed folds lost these or those veins the cell had been enclosed with. More specifically, r1 was desclerotized either anteriorly (Elmidae) or, together with an anteriorly desclerotized outer cell border (Limnichidae), posteriorly, or throughout, with a distinctly weakened apex of RA for accompaniment (Dryopidae, Heteroceridae). The following changes in the groundplan took place in both lineages in parallel: reduction of cu–a2 (Byrrhoidea but Larainae) and MP3+4, the latter down to a weak basal remnant at best (Byrrhoidea, except for Callirhipidae, Eulichadidae and perhaps some Ptilodactylidae), as well as the development of the “dryopiform” folding pattern (Helonariidae, Psephenidae and all dryopoids).

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To summarize, the interrelationships of byrrhoids seem to take the appearance (Eulichadidae + (Callirhipidae + ((Ptilodactylidae + Chelonariidae + Psephenidae) + Byrrhidae))) + (Elmidae + Dryopidae + Heteroceridae + Limnichidae). In this scheme, Callirhipidae and Eulichadidae share the wing type very close to, and supposedly derived from, the elateroid one. A long and narrow rc, a short and transverse r1, as well as the anterior corner of field D almost reaching the wing margin, warrant this similarity. The Eulichadidae is more primitive because some of its smaller representatives have retained the elaterid folding pattern. Yet some other wing characters of the Eulichadidae are derived, albeit may have emerged from a strong increase in body size, among them a reduced AA1+2+AA3a' and a not well-developed pcas. Based on this, the Eulichadidae is considered the sister to the remaining members of the psephenid lineage. The Ptilodactylidae among them is the most primitive in combining the complete venation of the clavus, except only for a reduced cu–a2, and the byrrhoid folding pattern. The same wing structure, including dmp, except for a derived venation (which is strongly reduced in the clavus while rc is very short and wide) and the sclerotization pattern of the apical membrane, argues the Byrrhidae as being closely allied to Ptilodactylidae. Both Psephenidae and Chelonariidae are immediate and more or less strongly specialized derivatives, respectively, of Ptilodactylidae, emerging from it either in parallel or in succession. The latter hypothesis seems more likely because apomorphies accumulated in the series Ptilodactylidae – Chelonariidae – Psephenidae. No clear-cut synapomorphies have been found in the psephenid lineage to support closer relationships between these or those families. On closer examination, the synapomorphies observed may prove to be homoplasies resulting from the shared tendencies to reducing r1, anal cells and veins in the clavus, these tendencies having obviously been induced by the miniaturization trend. Hence, it only remains to state that the wing of the least derived structure is that of Larainae, Elmidae. Buprestoidea + Dascilloidea. Sister-group relations of Buprestidae and Dascilloidea seem undisputed. Moreover, the incorporation of both into a single superfamily, Buprestoidea, seems possible. Dascillidae and Rhipiceridae show extremely close affinities, since the wing differences are nothing else but small details if any (cf. Figs A100 and 101). Forbes (1926) evaluated these differences at the generic level at most, elevating the Schizopodinae to a family of itself (Forbes, 1942). I disagree with him in thinking that the grounds for recognizing the Schizopodinae as the sister to the other buprestids are more weighty because both are more similar in wing structure, especially folding pattern, to each other than to Dascilloidea. Although the Rhinorhipidae remains incertae sedis, I suppose it to be the sister either to Buprestoidea plus Dascilloidea or even Buprestidae. In this I

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follow Lawrence et al. (1995a), not Lawrence (1988), for the wing characters as depicted in the latter paper (figs 16 and 17) in no way support a basal position of the Rhinorhipidae within the Elateroidea. Taken separately or combined, such characters as a long 2a with its lengthwise external border (AA3a"), the anterior two anals, AA1+2 and AA3a', shifted onto CuP, as well as a long and posterobasad oblique cu2 do not occur in the elateroid wing. Conversely, this character combination supplemented by a rather short field C and a short Mr is an integral part of the wing type of Buprestoidea s.l. (Figs A: 100, 102). Furthermore, if a supposedly field Ia has been depicted by the author correctly, it is a distinction of the buprestid folding pattern.

Bostrichoidea A few derived characters, partly homoplasies, developed on the basis of the cucujiform wing type, weakly support the monophyly of Bostrichoidea. More specifically, the bostrichoid folding pattern could have been formed in parallel at least twice, in Dermestidae and the other Bostrichoidea. Although advanced dermestids in many characters show a greater similarity to some bostrichoids than to primitive Dermestidae, the wings of Dermestidae are linked by transitions and can be described as belonging in a particular type. This dermestid wing type integrates a few but very special features, chiefly venational ones. These are first of all AA1+2 starting from 2a, i.e. from AA3a (Figs A110–113, synapomorphy?), not AA3a'. 2a in turn only rarely remains closed. Much more often it opens apically through a caudally released AA3a", a closed or open 2a often being special cases of individual variability (e.g. Dermestes); this instability is largely revealed in repeatedly forking anals. The above characters can be supplemented by field Af substituted for A, with the reservation that this feature is highly variable within Polyphaga and also shared with Anobiidae. Among the dermestids studied, Dermestes (Fig. A110) and Megatominae (Figs A: 112, 113) seem to be the least and the most derived, respectively, Orphilus being more or less intermediate. In general, the wing of the latter genus well corresponds to the cucujiform wing, being already advanced in some of its constituent parts. These are: the field B reduced to an indistinct fold, the distal costal pivot slightly internal and connected by a few convex or concave folds with the wing costal margin, the field G enlarged and split into two, an apicad broadened prs, a highly attenuate Mr, and mas lying close to and apically merged into MP3+4. In addition, aas–pcas is replaced with a wide, weakly sclerotized patch, perhaps a precursor of cas.

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Some of these traits, combined with the venation characteristic of the cucujiform wing type (primarily AA1+2 situated distal to 2a), must have been peculiar to the ancestor of the remaining Bostrichoidea. This had to combine wing characters of Endecatomidae and, especially, Nosodendridae. Such plesiomorphies of the latter family as a very large rc and cas of special shape and relative position argue in favour of this hypothesis. A closer relationship is here suggested between Nosodendridae and Anobiidae, including Ptininae, as well as between Endecatomidae and Bostrichidae. The first hypothesis is supported by such characters as the retention of the ams proximal part1, similarities in the structure of the cb distal part, the relative position of cas to SV (cf. Figs A114 and A119), a tendency towards the formation of the fields C+S+D and R+H (cf. Figs A114 and A117–119), and a strong, deltoid, postradial sclerotization (prs). The latter character is also observed in Endecatomidae, yet it seems to be outweighed by such synapomorphies of Endecatomidae + Bostrichidae as “Rr” shifted onto “r–m” and a fairly small rc. These are likely to be supplemented by an interrupted AA1+2+AA3a' base and the presence of the apical sclerotization, as. The monophyly of Anobiidae is supported by a particular wing type. It combines the anobiid folding pattern, a basally open rc and characteristic shapes and relative positions of prs, cas, SV and MP3+4. The vein MP3+4 extends basally into a narrow, usually rather strongly sclerotized and sometimes even vein-like (Mizodorcatoma) ams. Eucradinae + Ptininae stand against a background of the remaining Anobiidae studied. Both subfamilies show an obviously apotypic wing folding pattern (see above), coupled with both rc and cb of less derived structure and shape, and the veins not so strongly transformed as in other anobiids. Schematically, the genealogy of Bostrichoidea can be presented as Dermestidae + ((Nosodendridae +Anobiidae) + (Endecatomidae + Bostrichidae)).

Tenebrionoidea The wing groundplan of Tenebrionoidea seems to be the closest to that of Stenotrachelidae or Mordellidae, or a generalization of both. Plesiomorphies are as follows: the “clavicorn” folding pattern with a widely open field D, the presence of rms, rsp, anarc, a long and posterobasad directed cu2 and a full sclerotization 1

Since pushed outside the field C (C+S+D, etc.), this part of ams proximal to “rm” becomes increasingly vein-like and very similar to the MP3+4 base, being really conformable to the MP1+2 base (Fig. A117).

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pattern of the apical membrane. Yet the entire venation of the clavus and the subcubital binding patch combined occur in Zopheridae (Colydiinae), Pterogeniidae and, as indistinct traces, in Boridae, the latter family also retaining a not quite closed field B. This makes me inclined to place Stenotrachelidae + (Mordellidae + Rhipiphoridae) and Boridae–Zopheridae near the base of the tenebrionoid stem. When in the groundplan, the wings of Mordellidae and Rhipiphoridae fail to differ from each other (Figs A134–137). The main synapomorphies include a reduced rms, a rather short Mr, AA3a' shifted onto CuP–AA1+2, and a reduced 2a. Both lacking mas and anarc seem to be synapomorphies of Stenotrachelidae. The other taxa of Tenebrionoidea show a mosaic of plesio- and apotypic characters. Hence, the interrelationships of these groups with one another and the above families can be supported either by certain apomorphies or a few combined which result from the morphogenetic trends discussed above. The following groups are outlined based on wing structure. The first comprises Tetratomidae, Archeocrypticidae, Mycetophagidae, Ciidae probably included. The wing type the former three families share is defined by the following characters: cu2 reduced or transformed into the CuP base, a reduced “Rr”, coupled with Mr persisting still moderately long, mostly a well-developed or even strengthened (more seldom rudimentary) mas, a well-developed abs and a distinct MP3+4 which is slightly shifted forward at best. The radial cell is of moderate size. The sub-cubital binding patch is primitively present. The anterodistal component of ams as a remnant of rms is narrow and rather strongly sclerotized. Fields B and C almost conform to those of the tenebrionoid groundplan. These three families also share the following tendencies: (1) the development of secondary peripheral membrane gutters, or veinlets (Figs A149–151), and (2) reduction of 2a which starting point is a fusiform 2a, combined with AAP approaching AP3a apically. Some other polythetic characters such as a twofold abs (Figs A: 147, 150, 151), MP3+4 running parallel and close to the mcl anterodistal border (Figs A: 149, 151), a particular shape of aas–pcas or even of the entire sclerotization pattern of the apical membrane (Figs A149–151) add to the similarity. As it follows, Tetratomidae, Mycetophagidae and Archeocrypticidae are closely related. This holds especially true for the latter two families, since these fail to differ from each other, including the “eudryopiform” folding pattern and minor details of wing venation or sclerotization pattern. Wing characters argue also for Mycetophagidae + Archeocrypticidae to be recognized the closest to Hallomeninae, Tetratomidae, as Nikitsky (1993) has recently concluded from an analysis of imaginal and larval characters. On the other hand, Eustrophinae, Tetratomidae, seem to be the closest to Penthinae. The Ciidae is of special interest due to its very peculiar wing structure (Fig. A152). This is also nearly invariable across the family, implying that its larger

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members such as Xylographus could have descended from a smaller ancestor. More specifically, the wing is rather narrow, with a very long apical membrane and a short basal part almost devoid of a clavus plus jugum. The venation of the remigium’s basal part is reduced down to two axial bars, cb and CuA–CuA2, braced with an almost indistinct “r–m”. The clavus is supported by a complex longitudinal vein adjoining neither the wing margin nor a well-developed sbp. The apical membrane is reinforced with MP3+4 in couple with SV formed on the basis of pcas. Of the other primary sclerotized areas, only aas has persisted. The folding pattern is of the “eudryopiform” type. 3Ax is long and narrow, its head pointed and strongly curved. Firstly, almost all of these features are sure to have emerged through body miniaturization. Secondly, they make Ciidae virtually indistinguishable from some cucujoid families, e.g. Lathridiidae. Yet certain characters of Ciidae are uncharacteristic of cucujoid wings, a missing abs and the cb apex strongly broadened, curved backwards and set apart from the wing costal margin being among them. Hence, Ciidae can scarcely be placed elsewhere within Tenebrionoidea but close to Archeocrypticidae or Mycetophagidae, some smaller mycetophagids, e.g. Pseudotriphyllus or Berginus, already approximating to Ciidae in wing structure. The latter two genera show a narrow clavus supported or tending to be supported with a single longitudinal vein and a strongly to completely reduced jugal lobe, with Pseudotriphyllus also displaying the cb apical part similar to that of Ciidae. The other characters are either integral parts of the mycetophagid groundplan (the “eudryopiform” folding pattern, a more or less well-developed sbp, strong MP3+4 and aas–pcas) or may have been developed at earlier stages of mycetophagid evolution (cb apically broadened and drifted away from the wing margin). The next lineage is the tenebrionid one as embodying Tenebrionidae s.l., Ulodidae and Zopheridae, Monommatini and Colydiinae included (Ślipiński & Lawrence, 1999). A considerable character transgression being apparent, the lineage is defined by a combination of the following two tendencies: (1) towards MP3+4 supplanting mas, and (2) towards a strengthened strip aas–aas'. All members of the lineage tend to have field C slightly extended basad. Both 1a and 2a large, as well as a fairly long “Rr” (at least Tenebrionidae and Zopher, Zopheridae: Ślipiński & Lawrence, 1999, fig. 15), are among the symplesiomorphies. The stem-group seems to have been closer to Zopheridae (Fig. A153) some of whose representatives still retain a more or less full sclerotization pattern of the apical membrane, especially a distinct mas, a well-developed sub-cubital binding patch associated with CuP, and some other plesiomorphies. Yet a few evolutionary tendencies, partly depending on a decreased body size, are revealed in some members of the family. Totally reduced rc, “Rr” and Mr, the 2a growing smaller from apex to lacking (sometimes along with AP3a as in, e.g., Pycnomerus), cb dilated apically and AP4 bent (Figs A: 153, 154) are their immediate results.

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Sometimes, e.g. in Pycnomerus, certain sclerotizations, aas–aas' for example, strengthen up to sclerites. If some of the tendencies were realized combined in a hypothetic zopherid, its wing would be nothing else but that of Prostomidae (Fig. A155), except for an indistinctly sclerotized apical membrane and the “serricorn” folding pattern. Like Prostomidae, Ulodidae are here considered to be closely related to Zopheridae as well. The latter two families show very similar wing groundplans, including such synapomorphies as an obviously shortened Mr and, especially, cu2 reduced or transformed into the CuP base. Differences between them are negligible. Thus, Ulodes differs by the “hemidryopiform” folding pattern, an isolated sbp consequent upon the apical section of CuP reduced, and mas lacking following MP3+4 more strongly shifted forward; all these characters also occur in these or those Zopheridae. The Tenebrionidae contrasts with Ulodidae and Zopheridae in a particular combination of apo- and plesiomorphies. The main distinctive feature of the tenebrionid wing is a tridentate sclerotization pattern of the apical membrane which is composed of aas–aas', MP3+4 and pas, and separated from “r–m” owing to a reduced MP3+4 base (Figs A: 158–160, 162). The trident only reduced down to two anterior components (Figs A: 163, 164) appears to be a secondary condition. That pattern is supplemented by a lacking or, rarely, almost indistinct (Fig. A162) sbp, combined with such plesiomorphies as long Cur, cu2 and Mr, large 1a and 2a, as well as a transverse cu2, the latter character being if not a plesiomorphy then even an autapomorphy. This groundplan seems to have given rise to a great variety of derivatives, including highly specialized ones (Figs 164–166). When modified in a special way, the sclerotization pattern defines the next, pyrochroid lineage. This has emerged from the following two tendencies combined: (1) towards reinforced or even hypertrophied mas and pas, with MP3+4 reduced in between, and (2) towards subequally strengthened integrants of the aas'–aas–pcas strip which takes the appearance of a separate V-shaped pattern in front of fold la (Figs A168–184). These modifications were concurrent with the development of the “serricorn” folding pattern and the reduction of “Rr”, Mr, Cur and cu2. Besides this, AA3a' often approaches AAP while 2a gets strongly to completely reduced in size, mainly through becoming wedgy, with the posterior cell border opening up. The lineage includes Pythidae, Trictenotomidae, Pyrochroidae, Mycteridae, Anthicidae, Meloidae, Scraptiidae and Aderidae. Pythidae and Mycteridae are here recognized as the most primitive members of the lineage. In full measure this holds true for Pytho (Fig. A168) which retains such plesiomorphies as a large 2a, a long Mr, a distinct Cur, a rudimentary but visible cu2, and the entire, albeit weakened, sclerotization pattern of the apical membrane. On the contrary, Mycteridae complete tendency (1), but retain

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a distinct “Rr” and the “clavicorn” folding pattern. A short Mr, a wedgy 2a and, especially, a lacking sbp observed in some other mycterids are sure to be derived characters of Mycterus. Noteworthy is also a great but superficial similarity between Mycteridae and some Tenebrionidae in the sclerotization pattern of the apical membrane. The Mycteridae seems to be the closest to the Pyrochroidae which only differs by the “serricorn” folding pattern, combined with separate aas–aas' and mas (Figs A: 169, 170). An obliterated MP3+4 occurs only as a tendency, since it is absent from Pyrochroa, Schizotus and Tydessa, versus well-developed in Pedilus (Fig. A169). The latter pattern which constituent part is also a narrow sclerotization skirting the posterior margin of MP3+4 points to close relationships between Pyrochroidae and Pythidae. This small sclerotized patch was retained at the pas base in pyrochroids, MP3+4 having been lost (Fig. A170). The Trictenotomidae looks more peculiar unless probable sequels of size evolution are beyond consideration. Otherwise, large anal cells, well-developed Cur and cu2, a reinforced MP3+4, as well as weakened mas, pas and aas allow Trictenotomidae to be related to no other family but Pythidae. The wing of Pedilus supplemented by a V-shaped aas'–aas–pcas strip, yet distinctive in not so prominent mas and pas, is almost conformable to that of Stereopalpus (Fig. A176). It is this wing type that seems to be the groundplan of the lineage comprising Anthicidae, Meloidae, Scraptiidae and Aderidae, whereas the V-shaped strip a synapomorphy of all or at least the greater part of these families, Anaspididae probably also included. The above archetype is also supported by certain polythetic characters. As underlying tendencies, they seem to have appeared as the groundplan developed. As a result, Scraptiidae and some Anthicidae show MP3+4 reduced (Figs A179–181). Meloidae and some Anthicidae (Figs A176–178) are characterized by a posteriorly open 2a, whereas the remaining members of the lineage (Figs A179–184) display 2a reduced in a different way. In Aderidae, Anthicidae (Notoxus, Omonadus) and Meloidae, “r–m” involves additional elements in itself anteriorly and/or posteriorly, thus becoming a still more complex brace between cb and CuA–CuA2 than before. As it follows from a comparison between the above groups, firstly the wing of Stereopalpus fits in with the groundplan better than that of any other family does. Secondly, Anthicinae (Omonadus, Notoxus) and some Meloidae closely resemble each other. Scraptiidae, Aderidae, Steropinae, Macratriinae and Ischaliinae are very similar in wing structure, this holding especially true for the latter three taxa. The wing of Anaspididae (Fig. A184) sharply contrasts with that of the other groups of the pyrochroid–anthicid assemblage in plesiomorphies first of all, a very large rc and a well-developed, nearly vein-like rms being among them. From Scraptiidae which some authors consider as close relatives of the Anaspididae,

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this differs also by a less strongly modified sclerotization pattern of the apical membrane, i.e. a plesiomorphy as well. Among the other studied members of the assemblage, Anaspididae might be placed near certain Anthicidae (Fig. A179) showing a similar venation of the clavus, 2a reduced in size and an apically shortened AP3a. The AA3a' could have been reduced through its being merged into AAP or desclerotized from running close to AAP, which is deducible from the patterns observed in some Anthicidae or Meloidae (Figs A: 176, 178). The Salpingidae (Figs A: 172, 173, 175) is distinctive primarily in showing a hypertrophied mas. This is wide and at least basally sclerotized more strongly than adjacent sclerotizations are1. Besides this, pas is lacking to very small and separated from mas by a desclerotized MP3+4 (Istrisia), the latter vein being always developed. Characteristic are also the aas–pcas strip evenly sclerotized and associated with mas and usually also abs, as well as a V-shaped sclerotization composed of a very long and narrow ams, and the MP3+4 base lying close and parallel to mch. This combination is supplemented by the following plesiomorphies: the “clavicorn” folding pattern, a rather large, mostly long and narrow rc2 (Fig. A172; Sphaeriestes, Rabocerus), a long Mr (Fig. A173) and, in the groundplan (Istrisia), a more or less full venation of the clavus, except for Cur and also probably cu2 almost reduced. The present wing type is also supported by some trends in its further development: (1) towards the “eudryopiform” folding pattern (Sphaeriestes) through the salpingid one (Elacatis, Prostominia), and (2) towards the apical membrane reinforced with numerous secondary veinlets (Fig. A175; Inopeplus, Rabocerus). The salpingid wing type resembles that of Pyrochroidae–Mycteridae or, perhaps still more closely, Pythidae, implying very close affinities between these and Salpingidae. In addition, some Salpingidae share the salpingid folding pattern and almost identical venation and sclerotization patterns with Pterogeniidae (Fig. A174) which thus might be closely related to Salpingidae as well. Were it so, this could readily account for the association of the subcubital binding patch and the clavus’ anterior vein in the wing of Histanocerus because some miniature salpingids, e.g. Prostominia, show nearly the same pattern, namely, AA1+2 short and directly extended into a large sbp. In Salpingidae, the association of the vein with sbp is certainly secondary, as it stems from an increasingly narrow clavus in the course of the adult body growing smaller. Not so closely does the Pterogeniidae resemble the Mycetophagidae which is generally recognized as its ally. The presence of pas and a well-developed abs, as 1

2

When mas becomes desclerotized/depigmented in smaller beetles (Sphaeriestes, Rabocerus), MP3+4 and the fold la remain widely separated. The inner rc border, r1, is usually strongly desclerotized (apomorphy).

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well as the clavus venation modified in a different way, distinguishes between Mycetophagidae and Pterogeniidae. The remaining tenebrionoid families display no clear-cut apomorphies they share with one another or with the above groups. All of them show sbp originally combined with full venation except for the apical section of CuP, including cu2 oblique posterobasad and usually long. The latter symplesiomorphy is probably better to be considered as evidence of basal positions of Oedemeridae, Melandryidae, Synchroidae and Boridae among tenebrionoids. As for the relationships of these taxa, I can but put forth the following hypotheses. The complete sclerotization pattern of the apical membrane, with a strong but yet not too long aas–aas' and a well-developed, narrow, anterior component of ams as the rms remnant, suggests that Calopodinae, Oedemeridae, might be closer either to Stenotrachelidae–Mordellidae or Tetratomidae–Mycetophagidae, if anything. The remaining Oedemeridae studied (Figs A: 141, 142) are farther advanced because aas–aas' is strengthened and the remainder of the sclerotization pattern, including MP3+4, is entirely or partly reduced. A general weakness of the sclerotization pattern resulting in the borders blurred between its integrants is a distinctive feature of most of the Melandryidae. The venation of the remigium often also becomes weaker, thus leaving “Rr”, Mr and “r–m” reduced, as well as rc open basally or even totally desclerotized (e.g. Dircaea or Orchesia). As sharply contrasting with the other Melandryidae, Osphyinae show the sclerotization pattern very distinct and indeed strengthened (Fig. A145). Still it is the Synchroidae among Tenebrionoidea that is of special interest in displaying the most generalized wing structure. Such characters, especially when combined, as a fairly large rc, its long posterior border, RP+MA, a welldeveloped “Rr”, a long Mr and both long and posterobasad oblique cu2, as well as a distinct Cur provide evidence of affinities between Synchroidae and such tenebrionoids as, e.g., Melandryidae. At the same time, a strengthened strip aas– aas' (or perhaps aas–pcas) associated with a forward shifted MP3+4 is the grounds for placing the Synchroidae near the tenebrionid lineage. This holds also true for Boridae (Fig. A157; Lecontia: Wallace & Fox, 1980, fig. 152) which, besides, is barely different from Pythidae in wing structure.

Cucujoidea The Cucujoidea is here subdivided into a few groups, or lineages, each showing a particular wing type. These types are as follows. The protocucujid wing type (Protocucujidae and Sphindidae, Figs A: 185, 186) is here considered as the closest to the groundplan of the Cucujoidea, which

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follows from a long and vein-like rms beginning on a medially angulate “r–m”, combined with a still distinct mas. The former two characters, together with a general venation pattern and a tight, sclerite-like abs (Ericmodes), add to the similarity between this wing and that of Phytophaga. Apomorphies are only few and not conspicuous. These are mainly restricted to a fairly long apical membrane, a rather small jugum, a distinct jugal incision, neither Cur nor cu2 developed, a small 2a, and probably also a slightly shortened “Rr”. Like in many other Coleoptera, these characters are immediate evolutionary responses to body miniaturization. It seems to be this evolutionary factor that could have brought about profound change in wing structure in Sphindidae (cf. Fig. A186 and 187). The cucujid wing type (Cucujidae, Passandridae and Silvanidae, Figs A193– 195) is a slightly modified derivation of the previous one. It is supported by the following synapomorphies: 2a lacking probably through being proportionately decreased in size; the anterior three veins in the clavus appreciably weaker than the posterior two; folding pattern of or near the “serricorn” type; sbp rudimentary or missing (reduced). The presence of five apical veinal branches in the clavus and a short but vein-like remnant of rms are significant plesiomorphies. Such derived characters as a missing 2a and the anterior three veins weaker in the clavus suggest that larger members of the group might have descended from small-sized ancestors. Passandridae and Silvanidae seem to be more similar to each other than to Cucujidae. Virtually all characters of venation, folding and sclerotization patterns favour this. The main distinctions are a basally open rc, combined with a long and desclerotized “Rr”, as well as an apically more or less tridentate ams. The occurrence of the salpingid folding pattern in certain silvanids (Silvanus) could supposedly have given rise to the cryptophagid pattern. The laemophloeid wing type (Laemophloeidae and Propalticidae, Figs A: 196, 197) is almost certainly nothing else but a variant of the previous type resulting from body miniaturization, with the wing venation and sclerotization pattern of the apical membrane being only slightly modified. In particular, longitudinal veins were obliterated down either to four (cb, CuA–CuA2, (AA1+2+AA3)–AAP and AP4) or three, since the jugal lobe was reduced with the vein AP4 in support. An almost indistinct MP3+4 supports a very long apical membrane. A slightly angulate subapical curve of AP4 seems to be a synapomorphy of Laemophloeidae, Cucujidae, Passandridae and Silvanidae. The cryptophagid wing type (Cryptophagidae and Phloeostichidae, Figs A: 198, 199) appears to share the groundplan with the cucujid wing type, but it might have derived from this groundplan in a different way. The wing is narrow, with a small jugal lobe, a deep jugal incision and a long apical membrane sup-

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plied with MP3+4 and SV1 and/or SV2 in support. CuA2 is long, lengthwise and strongly desclerotized distal to where intersected by the fold hw; sbp is rudimentary or absent (apomorphy); the venation of the clavus and jugum is similar to that of the cucujid wing type. The main distinction is the cryptophagid folding pattern, as well as the characters consequent upon its development. As depicted in Leschen et al. (2005), Bunyastichus, Phloeostichidae, and Priasilphidae are indistinguishable in wing venation, shape and proportions if at all different in wing structure from the Cryptophagidae and Phloeostichidae here studied. The monotomid wing type (Monotomidae, Fig. A200) is of the same shape, proportions and the structure of the cubital spur as in the preceding type. I also think that the monotomid folding pattern is a special derivative of the cryptophagid one, which could have added to the similarity between the monotomid and cryptophagid wings types. Yet the somewhat different venation in the clavus and a large sbp (Rhizophagus) combined makes me relate Monotomidae rather to Byturidae–Biphyllidae or Erotylidae–Languriidae. The nitidulid wing type (Nitidulidae and Brachypteridae, Fig. A201) is similar in appearance to the previous one. Differences are few: no sbp, a little more strongly reduced venation in the clavus and the CuA2 attenuated but usually not desclerotized distal to the fold hw. The folding pattern seems to be of a different, staphyliniform, type which follows from certain slight if any differences between the nitidulid and monotomid wing types in the shape and position of the primary sclerotized areas. Namely, cs looks like a fairly long sclerite with its apex directed anterodistad, and ams is represented by its anterior component, the homologue of rms, which slightly penetrates into field S. Two pigmented patches near the costal margin of the apical membrane are also characteristic, one at its middle, the other in front of field D. Pigmented patches of similar position occur in the cucujid-laemophloeid wing type, as well as in Helota (Figs A: 193–196, 202). Helota also shares some other characters with Nitidulidae and allied families, the above described sclerotization pattern, as well as field C extended basad and very long distal to “r–m” being among them. The similarity between Nitidulidae and Phalacridae or some Languriidae (Fig. A203; Cryptophilus) in wing structure is restricted to CuA2 intersected at or near its base by the fold hw. The erotylid wing type (Erotylidae and Languriidae, Figs A190–192) differs from the superfamily groundplan scarcely more than the protocucujid wing type does. Yet the mosaic of plesiomorphies and apomorphies is different, since a large 2a and the entire field B are combined with a reduced, free apical section of CuP, a straight “r–m” and the rms replaced with ams. The impact of body miniaturization seems to have largely resulted in reduced 2a and rc or, sometimes, in

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CuA2 intersected by the fold hw (Cryptophilus), or the “eudryopiform” folding pattern developed (Leucohimatium). The endomychid wing type (Endomychidae, Coccinellidae, Corylophidae, Discolomatidae, Lathridiidae, Cerylonidae, Figs A206–209) is almost exclusively defined by apomorphies, but “Rr” and Mr are rather long in the groundplan. The wing is rather narrow, with a long apical membrane supported with MP3+4 posteriorly and one or two secondary veins, SV1 and SV2, anteriorly; rc mostly indistinct, being transformed into a more or less tightly sclerotized patch at the cb apex. The vein “r–m” usually lacking while CuA2 is strongly curved backward under the impact of the fold hw. The main distinction is the presence of only two, extreme, apical veinal branches, CuP–AA1+2 and AP3a, in the clavus, both short and connected by a complex vein beginning from a large 1a. The anterior branch is associated with sbp liable to further separation or reduction in some Endomychidae, Cerylonidae, Aphanocephalus, Discolomatidae, and probably also Corylophidae. A transverse aas and a sclerite-like abs usually occur among the central sclerotizations of the apical membrane. The folding pattern is of the “eudryopiform” type modified into the coccinellid pattern in some Endomychidae (Aphorista) and Coccinellidae (Fig. A208). The wings of some smallest members of the lineage (Lathridiidae, some Endomychidae and Cerylonidae) are scarcely distinguishable due to a combination of derived characters. These synapomorphies or, partly, homoplasies are as follows. The wing is stalky because of the apical membrane broadened apicad, a very narrow clavus and a missing jugum. The supporting bars are eventually restricted to cb, CuA–CuA2, and one or no (Cerylon) vein in the clavus. The latter vein if any either persists as S-shaped basally or unbent (Dexialia; Lathridiidae). 1a opens up through its desclerotized posterior border. The sclerotizations abs, aas and the MP3+4 base in the form of a narrow longitudinal sclerite are more often retained to support fields D, R and H, respectively. The lack of sbp in some Cerylonidae or Discolomatidae can be a derived character. Together with Bothrideridae, the members of the lineage involved have been recognized as those of the cerylonid series (Sen Gupta & Crowson, 1973). Bothrideridae are distinguished among the others by a generally less derived wing structure (Figs A: 204, 205). More specifically, sbp is lacking, the folding pattern is of the “diversicorn” type, and the apical veinal branches are three in the clavus in addition to an obliterated AP3a. Moreover, the clavus’ venational groundplan of at least some bothriderids (Fig. A205) tends to have evolved into a reinforced AAP, with apical branches reduced in front; this is rather characteristic of the cucujid lineage. This venation pattern seems to approach the only longitudinal vein remote from sbp which euxestine cerylonids show. What adds more to the similarity between Cerylonidae and Bothrideridae is

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also a basad extended field C, combined with partly to totally reduced fields A and B. This folding pattern occurs in Corylophidae (Fig. A209) as well, sharply contrasting with the patterns observed in the remaining families. Among them, Endomychidae and Coccinellidae are most closely related, this following from no differences in wing structure seen between them. Thus, there are no other derived characters shared by Bothrideridae and other families of the cerylonid series but a basal, S-shaped bending of the 1st anal vein and a few small details of the sclerotization pattern. To summarize, two or three groups could be outlined within this assemblage, either (Bothrideridae + Cerylonidae) + (Corylophidae + Endomychidae + Coccinellidae + Discolomatidae + Lathridiidae) or (Bothrideridae + Cerylonidae) + Corylophidae + (Endomychidae + Coccinellidae + Discolomatidae + Lathridiidae). Helotidae and Phalacridae among the remaining Cucujoidea are somewhat similar to each other. This similarity is chiefly due to a missing sbp and a somewhat reduced venation in the clavus (primarily CuP and 2a) against the background of a generally rather primitive wing structure. However, similar venation patterns occur not only in some cucujoids but also many other cucujiform beetles; therefore, homoplasy of some of them seems very likely. In full measure this holds true for some other wing characters. Among these of Phalacridae, the “clavicorn” folding pattern as a superfamily protofeature claims attention first, as well as a distinct ams, the CuA2 intersected by the fold hw and perhaps the pas present. Taken combined or separate, such characters as a well-developed pas and a small fragment Cur–CuP–cu2 detached from CuP attach an appreciable similarity to the wing of Helota and that of some Chrysomeloidea or Curculionoidea (Figs A: 214, 217). The byturid wing type (Byturidae and Biphyllidae, Figs A: 188, 189) sharply contrasts with the others in the combination of (1) a well-developed sbp associated with ?CuP, (2) a conspicuous pas, (3) the field S posterior corner situated caudal to MP3+4, and (4) an open field D. Among cucujiform beetles of a more or less similar wing structure, characters (1) and (2) are peculiar to Cucujoidea and Cleroidea, respectively, with character (2) occurring also in Chrysomeloidea. Character (3) is a feature, syn- if not autapomorphy, of Cleroidea, whereas character (4) is a basal plesiomorphy. Based on this, I cannot but suggest the Byturidae–Biphyllidae to be annectent between the Cucujoidea and the Cleroidea and, when placed within the Cucujoidea, a group of special status. The similarity between Byturidae–Biphyllidae and Cleroidea is emphasized by almost identical sclerotization patterns of the apical membrane, namely, the shapes and relative positions of the integrants of the SV1–SV2–aas–abs assemblage (cf. Fig. A189 with Figs A: 228, 229). That these two groups, or, more precisely, Byturidae and Trogossitidae, are close relatives, Leschen et al. (2005) have recently concluded from an analysis of imaginal and larval characters.

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Among Cucujoidea, the byturid wing type is only comparable with the protocucujid one (Sphindidae). Their particular wing shape and folding pattern of the wing apex seem to be the main characters shared by both. That the wings of Byturidae and Biphyllidae agree even in minor details adequately supports sister-group relations of these families and negates such deep parallelism as almost improbable.

Chrysomeloidea Cerambycidae and Chrysomelidae s.l. closely resemble each other in wing structure. The wing groundplan of Cerambycidae is almost conformable to that of Lepturinae while distinguishable from the wing groundplan of Chrysomeloidea by a complete set of apical veinal branches in the clavus and a missing sbp, this being also absent from many chrysomeloids. Eumolpinae or Lamprosomatinae among Chrysomelidae s.l. are of a nearly groundplan wing structure, whereas Hispinae, Chrysomelinae and Galerucinae are derived. Representatives of these three subfamilies can be ordered into an almost continuous series of successive venational reductions in the wing trailing area. In all of the above subfamilies, vein AA3–AA3b–AAP is primitively strongly curved due to a chiefly transversely directed AA3b. An indistinct or no curve defines Sagrinae, Bruchinae, Donaciinae, Criocerinae, Megalopodidae and Orsodacnidae, being a tentative wing synapomorphy of all or the greater part of these groups. In addition, the clavus venation is much more strongly reduced in these than in those taxa, but the wings of certain sagrines (Carpophagus: Jolivet, 1957) can probably be in accordance with the venational groundplan of Chrysomeloidea.

Curculionoidea Three lineages are more or less well traced within the Curculionoidea. The lineage embodying Belidae and Nemonychidae is of the least derived wing structure: fields R and H are large, R is not closed; the venation is full or almost so, including CuA2 long and/or not intersected by the fold hw, and a pentagonal rc with rsp; abs is tight, aas lacking, TV not yet formed. The wing of pachyurine belids is recognized as the least derived in most of the characters. The second lineage comprises Attelabidae, Anthribidae and Urodontidae. A tight aas triangular in shape which occupies the posteriormost part of field R is considered as a probable synapomorphy. Wing venation is still complete, with a

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pentagonal rc and the CuA2 either not intersected (Urodontidae) or intersected (Attelabidae, Anthribidae) by the fold. As a rule, field R is either not closed or with its anterior corner adjoining the wing costal margin. Apart from aas, Attelabidae and Anthribidae are very similar to each other in the sclerotization pattern of the apical membrane, especially its anterior part. The remainder of curculionoids form the third lineage. In these, the wing folding pattern is of the curculionid type, the CuA2 base is intersected by a fold; the wing venation is distinctly modified as often being strongly reduced in the clavus and jugum; aas occupies the entire, albeit small, field R, the aas anterodistal part is sclerite-like; TV is well-developed, strip-shaped. Oxycorynidae, Brentidae and Ithyceridae are only provisionally incorporated into this lineage. Among Curculionidae, Chrysolopus, Aterpinae (Zherikhin & Gratshev, 1995, fig. 151), is noteworthy as retaining the most complete venation in the clavus. A derived, brentid, folding pattern and the particular sclerotization pattern of the apical membrane it defines are synapomorphies of Brentidae (Brentinae, Apioninae and Nanophyinae).

Acknowledgements I thank the following coleopterists who provided me with material for study: Dr. N.B. Nikitsky (Zoological Museum, Moscow State University), the late Mr. V.G. Gratshev (Paleontological Institute, Russian Academy of Sciences, Moscow), Dr. A.G. Kirejtshuk (Zoological Institute, Russian Academy of Sciences, St. Petersburg), Dr. L.N. Medvedev, Dr. A.V. Kompantsev (both Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow), Dr. S.A. Kurbatov (All-Russia Center of Plant Qurantine, Bykovo, Moscow Region), Mr. S.V. Kazantsev (Moscow). I am especially obliged to Dr. A.G. Ponomarenko, Dr. D.E. Stcherbakov (both Paleontological Institute, Russian Academy of Sciences, Moscow) and again Dr. A.G. Kirejtshuk for their criticism on an earlier draft of this paper, as well as various helpful comments. Dr. F. Haas (Germany) and an anonymous reviewer kindly provided highly useful remarks on an advanced draft. My sincere gratitude also goes to my friend Dr. S.I. Golovatch for editing this book.

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REFERENCES Alexander R. (Александер Р.), 1970. Biomechanics (Биомеханика). Moscow, Mir. 339 p. (Russian translation). Arndt E. & Beutel R.G., 1995. Larval morphology of Systolosoma Solier and Trachypachus Motschulsky (Coleoptera: Trachypachidae) with phylogenetic considerations. – Entom. Scand., 26: 439–446. Baehr M., 1979. Vergleichende Untersuchungen am Skelett und an der Coxalmusculatur des Prothorax der Coleoptera. Ein Beitrag zur Klärung der phylogenetischen Beziehungen der Adephaga (Coleoptera, Insecta). – Zoologica, 44: 1–76. Balfour-Browne F., 1940. British Water Beetles, 1. London, Ray Society. XVII + 375 p. Balfour-Browne F., 1943. The wing venation of the Adephaga (Coleoptera) with special reference to the Hydradephaga and some homologies with the Polyphaga. – J. R. Microscop. Soc., 63: 55–64. Beklemishev V.N. (Беклемишев В.Н.), 1994. Methodology of Systematics (Методология систематики). Moscow, KMK Scientific Press. 250 p. (In Russian). Bell R.T., 1966. Trachypachus and the origin of the Hydradephaga (Coleoptera). – Coleopt. Bull., 20: 107–112. Bell R.T., 1998. Where do the Rhysodini (Coleoptera) belong? – In: Phylogeny and Classification of Caraboidea. Mus. reg. Sci. nat. Torino, Torino: 261–272. Bell R.T. & Bell J.R., 1962. The taxonomic position of the Rhysodidae. – Coleopt. Bull., 16: 99–106. Beutel R.G., 1991. Internal and external structures of the head of 3rd instar larvae of Amphizoa lecontei Matthews (Coleoptera: Amphizoidae). A contribution towards clarification of the systematic position of Amphizoidae. – Stuttgarter Beitr. Naturk., Ser. A, 469: 1–24. Beutel R.G., 1993. Phylogenetic analysis of Adephaga (Coleoptera) based on characters of the larval head. – Syst. Entom., 18: 127–147. Beutel R.G., 1995. The Adephaga (Coleoptera) phylogeny and evolutionary history. – In: Pakaluk J. & Ślipiński S.A., eds., Biology, Phylogeny and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Muzeum & Instytut Zoologii PAN, Warszawa: 174–217. Beutel R.G., 1997. Über Phylogenese und Evolution der Coleoptera (Insecta), insbesondere der Adephaga. – Verh. Naturwiss. Ver. Hamburg, N.F., 31: 1–64.

REFERENCES

251

Beutel R.G., 1998. Trachypachidae and the phylogeny of Adephaga (Coleoptera). – In: Phylogeny and Classification of Caraboidea. Mus. reg. Sci. nat. Torino, Torino: 81–106. Beutel R.G. & Haas A., 1996. Phylogenetic analysis of larval and adult characters of Adephaga (Coleoptera) using cladistic computer programs. – Entom. Scand, 27: 197–205. Beutel R.G. & Haas F., 2000. Phylogenetic relationships of the suborders of Coleoptera (Insecta). – Cladistics, 16: 103–141. Beutel R.G. & Leschen R.A.B., 2005. Phylogenetic analysis of Staphyliniformia (Coleoptera) based on characters of larvae and adults. – Syst. Entomol., 30: 510–548. Beutel R.G. & Roughley R.E., 1988. On the systematic position of the family Gyrinidae (Coleoptera: Adephaga). – Z. zool. Syst. Evolut.-forsch., 26: 380–400. Blum P., 1979. Zur Phylogenie und ökologischen Bedeutung der Elytrenreduktion und Abdomenbeweglichkeit der Staphylinidae (Coleoptera). Vergleichend- und funktionsmorphologische Untersuchungen. – Zool. Jb., Anat., 102 (4): 533–582. Brackenbury J.H., 1994. Wing folding and free-flight kinematics in Coleoptera (Insecta): a comparative study. – J. Zool., London, 232 (2): 253–283. Brodsky A.K. (Бродский А.К.), 1979. Evolution of the stone-fly wing apparatus (Plecoptera), Part III. Functional morphology of the wings (Эволюция крылового аппарата веснянок (Plecoptera), Часть I. Функциональная морфология крыльев). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 58 (1): 69–77. (In Russian). Brodsky A.K. (Бродский А.К.), 1981. Evolution of the stone-fly wing apparatus (Plecoptera), Part III. Wing deformations in the stone-fly Isogenus nubecula Newm. during flight (Эволюция крылового аппарата веснянок (Plecoptera), Часть III. Деформация крыльев веснянки Isogenus nubecula Newm. во время полета). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 60 (3): 523–534. (In Russian). Brodsky A.K. (Бродский А.К.), 1982. Evolution of the stone-fly wing apparatus (Plecoptera), Part IV. Wing kinematics and a general conclusion (Эволюция крылового аппарата веснянок (Plecoptera), Часть IV. Кинематика крыльев и общее заключение). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 61 (3): 491–500. (In Russian). Brodsky A.K. (Бродский А.К.), 1986. Insect flight with high-frequency wing flapping (Полет насекомых с высокой частотой взмахов крыльев). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 65 (2): 269–279. (In Russian). Brodsky A.K. (Бродский А.К.), 1987. Structure and functional significance of veins and folds in the insect wing (Строение и функциональное значение жилок и складок крыльев насекомых). – In: Morphological Foundations of Insect Phylogeny (Морфологические основы филогении насекомых). Proceedings of the All-Union Entomological Society (Труды ВЭО), 69: 4–19. (In Russian). Brodsky A.K. (Бродский А.К.), 1988. Flight Mechanics of Insects and the Evolution of Their Wing Apparatus (Механика полета насекомых и эволюция их крылового аппарата). Leningrad, Leningrad University Press. 208 p. (In Russian).

252

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Brodsky A.K. (Бродский А.К.), 1989. Structure, functioning and evolution of insect wing articulations (Строение, функционирование и эволюция крыловых сочленений насекомых). – In: Lectures in Memoriam N. A. Cholodkowsky (Чтения памяти Н.А. Холодковского). Leningrad, Nauka: 3–47. (In Russian). Brodsky A.K., 1994. The Evolution of Insect flight. Oxford, Oxford University Press. 229 p. Brodsky A.K. & Ivanov V.D. (Бродский А.К. и Иванов В.Д.), 1983. A functional evaluation of insect wing structure (Функциональная оценка строения крыльев насекомых). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 62 (1): 48–64. (In Russian). Browne D.J. & Scholtz C.H., 1994. The morphology and terminology of the hindwing articulation and wing base of the Coleoptera, with specific reference to the Scarabaeoidea. – Systematic Entomology, 19: 133–143. Browne D.J. & Scholtz C.H., 1996. The morphology of the hind wing articulation and wing base of the Scarabaeoidea (Coleoptera), with some phylogenetic implications. – Bonner Zoologische Monographien, 40: 1–200. Browne D.J. & Scholtz C.H., 1999. A phylogeny of the families of Scarabaeoidea. – Syst. Entomol., 23: 51–84. Browne D.J., Scholtz C.H. & Kukalová-Peck J., 1993. Phylogenetic significance of wing characters in Trogidae (Coleoptera: Scarabaeoidea). – Afr. Entomol., 1: 195–206. Burmeister E.-G., 1976. Der Ovipositor der Hydradephaga (Coleoptera) und seine phylogenetische Bedeutung unter besonderer Berücksichtigung der Dytiscidae. – Zoomorphologie, 85: 165–257. Burmeister H, 1841. Observations sur les affinités naturelles de la famille des Paussidae. – Magasin Zool., Paris: 1–15. Burmeister H, 1854. Untersuchungen über die Flügtypen der Coleopteren. – Abhandl. Naturf. Ges. Halle, 2: 125–140. Calder A.A., 1990. Anthracalaus australis Fleutiaux, a little-known Australian elaterid (Coleoptera: Elateridae), with a key to related genera. – Invertebrate Taxon., 3: 551–563. Calder A.A., Lawrence J.F. & Trueman J.W.H., 1993. Austrelater, gen. nov. (Coleoptera: Elateridae), with a description of the larva and comments on elaterid relationships. – Invertebrate Taxon., 7: 1349–1394. Caterino M.S., Hunt T. & Vogler A.P., 2005. On the constitution and phylogeny of Staphyliniformia (Insecta: Coleoptera). – Molecular Phylogenetic and Evolution, 34: 655–672. Caterino M.S. & Vogler A.P., 2002. The phylogeny of the Histeroidea (Coleoptera: Staphyliniformia). – Cladistics, 18: 394–415. Comstock J.H., 1918. The Wings of Insects. Ithaca, NY, Comstock. 430 p. Comstock J.H. & Needham J.G. 1898–1899. The wings of insects. – American Naturalist, 32: 43–48, 81–89, 231–257, 335–340, 413–424, 561–565, 769–777, 903–911. Crowson R.A., 1955. The Natural Classification of the Families of Coleoptera. London, Lloyd & Co. 187 p.

REFERENCES

253

Crowson R.A., 1960. The phylogeny of Coleoptera. – Annual Review of Entomology, 5: 111–134. Crowson R.A., 1971. Some problems in the phylogenetic classifications of the Coleoptera. – Proc. XIII Internat. Congr. of Entomology (Moscow, 2–9 August 1968), 1: 235–237. Crowson R.A., 1975. The evolutionary history of Coleoptera, as documented by fossil and comparative evidence. – Atti del Congresso Nazionale Italiano di Entomologia, Sassari, 20–25 Maggio 1974, Firenze, Italy: 47–90. Dettner K., 1985. Ecological and phylogenetic significance of defensive compounds from pygidial glands of Hydradephaga (Coleoptera). – Proc. Acad. Nat. Sci. Philadelphia, 137: 156–171. Deuve T., 1993. L’abdomen et les genitalia des femelles de Coléoptères Adephaga. – Mém. Mus. Natn. Hist. Nat., 155 (Zool.): 1–184. d’Orchymont A., 1920. La nervation alaire des Coléoptères. – Annales de la Société entomologique de France, 89: 1–50, pls 1–3. d’Orchymont A., 1921. Aperçu de la nervation alaire des Coléoptères. – Annales de la Société entomologique de Belgique, 61: 256–278. Dolin V.G. (Долин В.Г.), 1975. Wing venation in click-beetles (Coleoptera, Elateridae) and its significance in the systematics of the family (Жилкование крыльев жуковщелкунов (Coleoptera, Elateridae) и его значение для систематики семейства). – Zoologicheskii zhurnal (Зоологический журнал), 54 (11): 1618–1633. (In Russian). Dolin V.G. (Долин В.Г.), 2000. The importance of larval characters and venation in the systematics of Elateroidea (Coleoptera) (Значение личиночных признаков и жилкования крыльев в систематике Elateroidea (Coleoptera)). – In: Lectures in Memoriam N. A. Cholodkowsky (Чтения памяти Н.А. Холодковского). St. Petersburg, Nauka: 1–49. (In Russian). Emelianov A.F. (Емельянов А.Ф.), 1977. Homology of wing structures in cicadeans and primitive Polyneoptera (Гомология крыловых структур у цикадовых и примитивных Polyneoptera). – In: Morphological Foundations of Insect Systematics (Морфологические основы систематики насекомых). Proceedings of the AllUnion Entomological Society (Труды ВЭО), 58: 3–48. (In Russian). Erwin T.L., 1985. The taxon pulse: a general pattern of lineage radiation and extinction among carabid beetles. – In: Ball G.E., Ed., Taxonomy, Phylogeny and Zoogeography of Beetles and Ants. Dordrecht, etc., W. Junk: 437–473. Erwin T.L., 1991. The ground-beetles of Central America (Carabidae), Part II: Notiophilini, Loricerini, and Carabini. – Smithsonian Contrib. Zool., 501: I–III + 1–30. Fedorenko D.N., 2002. The coleopteran wing: some notes on the structure of the articular area, with reference to the nomenclature of wing venation. – Russ. Entomol. J., 11 (1): 5–14. Fedorenko D.N. (Федоренко Д.Н.), 2003. The coleopteroid wing: On the effect of the folding system on the origin of remigium venation (Колеоптероидное крыло: о

254

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

влиянии системы складок на генезис жилкования ремигиума). – Zoologicheskii zhurnal (Зоологический журнал), 82 (2): 1–15. (In Russian). Fedorenko D.N. (Федоренко Д.Н.), 2004a. The folding system of beetle wings and its main types. Communication 1 (Система складок крыльев жуков и ее основные типы. Сообщение 1). – Zoologicheskii zhurnal (Зоологический журнал), 83 (6): 693–700. (In Russian). Fedorenko D.N. (Федоренко Д.Н.), 2004b. The folding system of beetle wings and its main types. Communication 2 (Система складок крыльев жуков и ее основные типы. Сообщение 2). – Zoologicheskii zhurnal (Зоологический журнал), 83 (7): 795–808. (In Russian). Fedorenko D.N. (Федоренко Д.Н.), 2006. Venation of the clavus and jugum in Coleoptera wings and its origin (Жилкование клавуса и югума крыльев Coleoptera и его генезис). – Zoologicheskii zhurnal (Зоологический журнал), 85 (12): 1433–1446. (In Russian). Forbes W.T.M., 1922. The wing-venation of the Coleoptera. – Ann. Entomol. Soc. Amer., 15 (4): 328–345, pls XXIX–XXXV. Forbes W.T.M., 1924. How a beetle folds its wings. – Psyche, 31: 254–258. Forbes W.T.M., 1926. The wing folding patterns of the Coleoptera. – J. N.Y. Entomol. Soc., 34 (1): 42–68; (2): 91–139. Forbes W.T.M., 1942. The wing of Schizopini (Coleoptera: Dascillidae). – Entomol. News, 53: 101–102. Forsyth D.J., 1968. The structure of the defence glands in the Dytiscidae, Noteridae, Haliplidae and Gyrinidae (Coleoptera). – Trans. Roy. Entomol. Soc. London, 120 (6): 159–182. Forsyth D.J., 1970. The structure of the defence glands of the Cicindelidae, Amphizoidae and Hygrobiidae (Insecta: Coleoptera). – J. Zool., 160: 51–69. Ganglbauer L., 1892. Die Käfer von Mitteleuropa, 1. Wien. III + 557 S. Good H.C., 1925. Wing venation of Buprestidae. – Annals of the Entomological Society of America, 18: 251–276. Goodliffe F.D., 1939. The taxonomic value of wing-venation in the larger Dytiscidae. – Trans. Soc. Brit. Ent., 6: 23–38. Graham S.A., 1922. A study of the wing-venation of the Coleoptera. – Annals of the Entomological Society of America, 15: 191–200. Grodnitsky D.L. (Гродницкий Д.Л.), 1996. Adaptations to flapping flight in various holometabolous insects (Адаптация к машущему полету у различных насекомых с полным превращением). – Zoologicheskii zhurnal (Зоологический журнал), 75 (5): 692–700. (In Russian). Grodnitsky D.L., 1999. Form and Function of Insect Wings: The Evolution of Biological Structures. Baltimore, MD, Johns Hopkins University Press. 261 p. Grodnitsky D.L. & Morozov P.P., 1994. Morphology, flight kinematics and deformation of the wings in holometabolan insects (Insecta: Oligoneoptera + Scarabaeiformes). – Russ. Entomol. J., 3 (3–4): 3–32.

REFERENCES

255

Grodnitsky D.L. & Morozov P.P. (Гродницкий Д.Л. и Морозов П.П.), 1995. The vortical trace of a flying beetle (Вихревой след летящего жука). – Zoologicheskii zhurnal (Зоологический журнал), 74 (3): 66–72. (In Russian). Gurjeva E.L. (Гурьева Е.Л.), 1979. Click-beetles (Elateridae). The Subfamily Eliateribnae, the Tribes Megapenthini, Physorhinini, Ampedini, Elaterini, Pomachilini (Жуки-щелкуны (Elateridae). Подсемейство Elaterinae, трибы Megapenthini, Physorhinini, Ampedini, Elaterini, Pomachilini). – Fauna SSSR (Фауна СССР), Coleoptera, 12 (4). Leningrad, Nauka. 453 p. (In Russian). Haas F., 1998. Geometrie, Mechanik und Evolution der Flügelfaltung bei den Coleoptera (Insecta). PhD Thesis. Jena. Haas F., 2006. Evidence from folding and functional lines of wings on inter-ordinal relationships in Pterygota. – Arthropod Systematics & Phylogeny, 64 (2): 149–158. Haas F. & Beutel R.G., 2001. Wing folding and the functional morphology of the wing base in Coleoptera. – Zoology, 104: 123–141. Haas F., Gorb S. & Blikhan R., 2000. The function of resilin in beetle wings. – Proc. R. Soc. London, Ser. B, 267: 1375–1381. Haas F. & Kukalová-Peck J., 2001. Dermaptera hindwing structure and folding: new evidence for familial, ordinal and superordinal relationships within Neoptera (Insecta). – Eur. J. Entomol., 98: 445–509. Haas F. & Wootton R.J., 1996. Two basic mechanisms in insect wing folding. – Proc. R. Soc. London, Ser. B, 263: 1651–1658. Hamilton K.G.A., 1971. The insect wing. Part I. Origin and development of wings from pronotal lobes. – Journal of the Kansas Entomological Society, 44: 421–433. Hamilton K.G.A., 1972a. The insect wing, part II. Vein homology and the archetypal insect wing. – J. Kansas Entomol. Soc., 45 (1): 54–58. Hamilton K.G.A., 1972b. The insect wing, part IV. Venational trends and the phylogeny of the winged orders. – J. Kansas Entomol. Soc., 45 (3): 295–308. Hammond P.M., 1979. Wing-folding mechanisms of beetles, with special reference to investigations of adephagan phylogeny. – In: Erwin T.L., Ball G.E., Whitehead D.R. & Halpern A.L., eds, Carabid Beetles: Their Evolution, Natural History, and Classification. Dordrecht, etc., W. Junk: 113–180. Hansen M., 1995. Evolution and classification of Hydrophiloidea – a systematic review. – In: Pakaluk J. & Ślipiński S.A., eds, Biology, Phylogeny and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Warszawa, Muzeum & Instytut Zoologii PAN: 321–353. Hansen M., 1997. Phylogeny and classification of the staphyliniform beetle families (Coleoptera). – Det Kongelige Danske Videnskabernes Selskab. Biologiske Skrifter, 48. Copenhagen, Munksgaard. 340 p. Heberdey R.F., 1938. Beiträge zum Bau des Subelytralraumes und zur Atmung der Coleopteren. – Z. Morphol. Ökol. Tiere, 33: 667–734.

256

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Hörnschemeyer T., 1998. Morphologie und Evolution des flügelgelenks der Coleoptera und Neuropterida. – Bonn. Zool. Monograph, 43. Bonn, Zoologisches Forschungsinstitut und Museum Alexander Koenig. 127 p. Jolivet P., 1957. Recherches sur l’aile des Chrysomeloidea (Coleoptera). – Mém. Inst. R. Sci. Nat. Belg. Bruxelles. 2me Série, 51 (1): 1–180, pls I–XX. Jolivet P., 1959. Recherches sur l’aile des Chrysomeloidea (Coleoptera). – Mém. Inst. R. Sci. Nat. Belg. Bruxelles. 2me Série, 58 (2): 1–152, pls XXI–XL. Kavanaugh D.H., 1982. Notikasiini – a new tribe of Carabidae (Coleoptera) from Southeastern South America. – Coleopt. Bull., 36 (4): 549–566. Kavanaugh D.H., 1986. A systematic review of amphizoid beetles (Amphizoidae: Coleoptera) and their phylogenetic relationships to other Adephaga. – Proc. Calif. Acad. Sci., 44: 67–109. Kavanaugh D.H. & Erwin T.L., 1991. The tribe Cicindini Bänninger (Coleoptera, Carabidae): compatrative morphology, classification, natural history, and evolution. – Proc. Entomol. Soc. Wash., 93 (2): 356–389. Kempers K.J.W., 1924. Das Flügelgeäder der Käfer. – Entomol. Mitt., 13: 45–63. King E.W., 1956. Wing venation in the Adephaga and its contributions to phylogeny. – Iowa Academy of Sciences, 63: 697–699. Khalaf K.T., 1970. Wing venation and phylogenetic relationships in Mordellidae (Coleoptera, Heteromera). – Florida Entom., 53: 153–160. Kirejtshuk A.G., 1999. Sikhotealinia zhiltzovae Lafer, 1996 – recent representative of the Jurassic coleopterous fauna (Coleoptera, Archostemata, Jurodidae). – Proc. Zool. Inst. Russ. Acad. Sci., 281: 21–26. Klausnitzer B., 1975. Probleme der Abgrenzung von Unterordnungen bei den Coleoptera. – Entomol. Abh. Mus. Tierk. Dresden, 40: 269–275. Kolbe H., 1901. Vergleichend-morphologishe Untersuchungen an Koleopteren nebst Grundlagen zu einem System und zur Systematik derselben. – Archiv für Naturgeschichte, 67A: 98–112, 128–141. Kolbe H., 1908. Mein System der Coleopteren. – Zeitschrift für Wissenschaftliche Insektenbiologie, 4: 116–123, 153–162, 219–226, 246–251, 286–294, 389–400. Krell F.-T., 2006. Fossil record and evolution of Scarabaeoidea (Coleoptera: Polyphaga). – Coleopt. Soc. Monogr., 5: 120–143. Kryzhanovskij O.L. (Крыжановский О.Л.), 1983. The Beetle Suborder Adephaga: the Families Rhysodidae, Trachypachidae; the Family Carabidae (Introductory Part and a Review of the USSR Fauna) (Жуки подотряда Adephaga: семейства Rhysodidae, Trachypachidae; семейство Carabidae (вводная часть и обзор фауны СССР). – Fauna SSSR (Фауна СССР), Coleoptera, 1 (2). Leningrad, Nauka. 341 p. (In Russian). Kryzhanovskij O.L. & Reichardt A.N. (Крыжановский О.Л. и Рейхардт А.Н.), 1976. The Beetle Superfamily Histeroidea (the Families Sphaeritidae, Histeridae, Synteliidae). (Жуки надсемейства Histeroidea (семейства Sphaeritidae, Histeridae,

REFERENCES

257

Synteliidae)). – Fauna SSSR (Фауна СССР), Coleoptera, 5 (4). Leningrad, Nauka. 435 p. (In Russian). Kukalová-Peck J., 1978. Origin and evolution of insect wings and their relation to metamorphosis, as documented by fossil record. – Journal of Morphology, 156: 53–126. Kukalová-Peck J., 1983. Origin of the insect wing and wing articulation from the arthropodan leg. – Canadian Journal of Zoology, 61 (7): 1618–1669. Kukalová-Peck J., 1991. Fossil history and evolution of hexapod structures. – In: Insects of Australia. A Textbook for Students and Research Workers. 2nd edition, 1. CSIRO. Carlton, Melbourne University Press: 141–179. Kukalová-Peck J. & Lawrence J.F., 1993. Evolution of the hind wing in Coleoptera. – Can. Entomol., 125: 181–258. Kukalová-Peck J. & Lawrence J.F., 2004. Relationships among coleopteran suborders and major endoneopteran lineages: evidence from hind wing characters. – Eur. J. Entomol., 101: 95–144. Lafer G.S. (Лафер Г.Ш.), 1996. The fam. Sikhotealiniidae Lafer, fam. n. (Сем. Sikhotealiniidae Lafer, fam. n.). – In: Identification Book of the Insects of the USSR Far East (Определитель насекомых Дальнего Востока СССР), 3 (3). Vladivostok, Dal’nauka: 390–396. (In Russian). Lameere A., 1923. On the wing-venation of insects. – Psyche, 30 (4): 123–132. Laurent L., 1967. La sous-famille Tetralobinae (Coleoptera, Elateridae). – Bull. Ann. Soc. Ent. Belg., 103: 83–109. Lawrence J.F., 1988 (for 1987). Rhinorhipidae, a new beetle family from Australia, with comments on the phylogeny of the Elateriformia. – Invertebrate Taxonomy, 2: 1–53. Lawrence J.F., 1995. Electribius Crowson: alive and well in Mesoamerica, with notes on Ctesibius Champion and the classification of Artematopodidae. – Eds. Pakaluk J., Ślipiński S.A. Biology, Phylogeny and Classification of Coleoptera: Papers celebrating the 80th Birthday of Roy A. Crowson. Muzeum, Institut Zoologii PAN, Warszawa. P. 411–431. Lawrence J.F. & Newton A.F. Jr., 1982. Evolution amd classification of beetles. – Annu. Rev. Ecol. Syst., 13: 261–290. Lawrence J.F. & Newton A.F. Jr., 1995. Families and subfamilies of Coleoptera (with selected genera, notes, references and data on family-group names). – In: Pakaluk J. & Ślipiński S.A., eds, Biology, Phylogeny and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Warszawa, Muzeum & Instytut Zoologii PAN: 779–1006. Lawrence J.F., Nielsen E.S. & Mackerras I.M., 1991. Skeletal anatomy and key to orders. – In: Insects of Australia. A Textbook for Students and Research Workers. 2nd edition, 1. CSIRO. Carlton, Melbourne University Press: 3–32. Lawrence J.F., Nikitsky N.B. & Kirejtshuk A.G., 1995a. Phylogenetic position of Decliniidae (Coleoptera, Scirtoidea) and comments on the classification of Elateriformia

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EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

(sensu lato). – In: Pakaluk J. & Ślipiński S.A., eds, Biology, Phylogeny and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Warszawa, Muzeum & Instytut Zoologii PAN: 375–410 Lawrence J.F., Ślipiński S.A. & Pakaluk J., 1995b. From Latreille to Crowson: a history of the higher-level classification of beetles. – In: Pakaluk J. & Ślipiński S.A., eds, Biology, Phylogeny and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Warszawa, Muzeum & Instytut Zoologii PAN: 87–154. Leschen R.A.B., Lawrence J.F. & Ślipiński S.A., 2005. Classification of basal Cucujoidea (Coleoptera: Polyphaga): cladistic analysis, keys and review of new families. – Invertebrate Syst., 19: 17–73. Lyubarsky G.Y. (Любарский Г.Ю.), 1996. The Archetype, Style and Rank in Biological Systematics (Архетип, стиль и ранг в биологической систематике). Moscow, KMK Scientific Press. 434 p. (In Russian). Maddison D.R., Baker M.D. & Ober K.A., 1999. Phylogeny of carabid beetles as inferred from 18S ribosomal DNA (Coleoptera: Carabidae). – Syst. Entomol., 24 (2): 103–138. Magnan A., 1934. La locomotion chez les animaux, 1. Le vol des insectes. Paris, Herman & Co. 186 p. Maŕan J., 1930. Fylogenetická a systematická studie o čeledi cerambycidae založená na morfologii nervatury spodních kŕídel. – Sborn. entomol. odd. Národn. Mus. v Praze, 8: 20–50. Marçu O., 1939. Die Stellung im System und phylogenetische Entwicklung der Coccinellidae aufgrund vergleichender Untersuchungen des Flügelgeäders. – Anal. Acad. Române, 15: 1–27. Marden J.H., 1987. Maximum lift production during take-off in flying animals. – J. Exp. Biol., 130: 235–258. Martynov A.V., 1925. Über zwei Grundtypen der Flügel bei Insekten und ihre Evolution. – Zeitschrift für Morphologie and Ökologie der Tiere, 4: 465–501. Martynova O.M. (Мартынова О.М.), 1960. On wing venation in lepidopterans (Lepidoptera) (О жилковании крыльев у чешуекрылых (Lepidoptera)). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 39 (2): 296–299. (In Russian). Meyen S.V. (Мейен С.В.), 1978. The basic aspects of the typology of organisms (Основные аспекты типологии организмов). – Zhurnal obshchey biologii (Журнал общей биологии), 39 (4): 495–508. (In Russian). Nachtigall W., 1964. Zur Aerodynamik des Coleopterenfluges: Wirken die Elytren als Tragflügel? – Verhandl. deutsch. zool. Ges. Kiel, 58: 319–326. Nikitsky N.B. (Никитский Н.Б.), 1993. The Mycetophagid Beetles (Coleoptera, Mycetophagidae) in the Fauna of Russian and Adjacent Countries (Жуки-грибоеды (Coleoptera, Mycetophagidae) фауны России и сопредельных стран). Moscow, Moscow University Press. 184 p. (In Russian). Nikolajev G.V. (Николаев Г.В.), 1995. Material to the systematics of the subfamily Ochodaeinae (Coleoptera, Scarabaeidae) (Материалы к систематике

REFERENCES

259

подсемейства Ochodaeinae (Coleoptera, Scarabaeidae)). – Zoologicheskii zhurnal (Зоологический журнал), 74 (8): 72–82. (In Russian). Nikritin L.M. (Никритин Л.М.), 1977. The family Scarabaeidae (Семейство Scarabaeidae). – In: Mesozoic Beetles (Мезозойские жесткокрылые). Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, Nauka, 161: 119–130. (In Russian). Norberg R.Å., 1972. The pterostigma of insect wings, an inertial regulator of wing pitch. – J. Comp. Physiol. 81: 9–22. Ober K.A., 2002. Phylogenetic relationships of the carabid subfamily Harpalinae (Coleoptera) based on molecular sequence data. – Mol. Phyl. Evolution, 24 (2): 228–248. Ochs G., 1926. Die Dineutini. 2. Tribus der Unterfam. Enhydrinae, Fam. Gyrinidae (Col.). A. Allgemeiner Teil. – Entomol. Zeitschr., Frankfurt a.M., 40: 61–74, 112–126, 129–140, 190–197. Ochs G., 1969. Zur Ethökologie der Taumelkäfer (Col., Gyrinoidea). – Arch. Hydrobiol., Suppl. 35 (4): 373–410. Parreira M.H. & Casari S.A., 2004. Morphology of three Brazilian species of Semiotus (Coleoptera, Elateridae, Semiotinae). – Iheringia, Ser. Zool., Porto Alegre, 94 (3): 285–294. Pasqual C., 1982. Tipologia morfofunzionale dell’ala nei coleotteri coccinellidi. – Bolletino della Società Entomologica Italiana, 114: 113–116. Ponomarenko A.G. (Пономаренко А.Г.), 1969. A Historical Development of Archostematan Beetles (Историческое развитие жесткокрылых-архостемат). – Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, Nauka, 125. 239 p. (In Russian). Ponomarenko A.G. (Пономаренко А.Г..), 1972. On the nomenclature of beetle wing venation (Coleoptera) (О номенклатуре жилкования крыльев жуков (Coleoptera)). – Entomologicheskoe obozrenie (Энтомологическое обозрение), 51 (4): 768–775. (In Russian). Ponomarenko A.G. (Пономаренко А.Г.), 1973. On the division of the beetle order into suborders (О делении отряда жесткокрылых на подотряды). – In: Problems of Insect Palaeontology (Вопросы палеонтологии насекомых). Lectures in Memoriam N. A. Cholodkowsky (Чтения памяти Н.А. Холодковского). Leningrad, Nauka: 78–89. (In Russian). Ponomarenko A.G. (Пономаренко А.Г.), 1975. Coptoclava (Coleoptera), a peculiar Early Cretaceous aquatic beetle from eastern Asia (Coptoclava (Coleoptera) – своеобразный раннемеловой водный жук из Восточной Азии). – In: Fossil Fauna and Flora of Mongolia (Ископаемая фауна и флора Монголии). Proceedings of the Joint SovietMongolian Paleontological Expedition (Труды совместной советско-монгольской палеонтологической экспедиции). Moscow, Nauka, 2: 122–139. (In Russian). Ponomarenko A.G. (Пономаренко А.Г.), 1977. The Suborder Adephaga (Подотряд Adephaga). – In: Mesozoic Beetles (Мезозойские жесткокрылые). Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, Nauka, 161: 17–104. (In Russian).

260

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Ponomarenko A.G., 2002. Superorder Scarabaeidea Laicharting, 1781. Order Coleoptera Linné, 1758. The Beetles. – In: Rasnitsyn A.P. & Quicke D.L.J., eds, History of Insects. Dordrecht, etc., Kluwer Academic Publishers. 164–176 (517 p., 503 figs). Procházka R., 1936. Studie k morphologickému a systematickému vÿznamu nervatury kridel u malacodermat. – Acta Entom. Mus. Pragae, 14: 100–132. Rasnitsyn A.P. (Расницын А.П.), 1969. The Origin and Evolution of Lower Hymenopterans (Происхождение и эволюция низших перепончатокрылых). – Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, Nauka, 123: 1–196 (In Russian). Rasnitsyn A.P. (Расницын А.П.), 1980a. The Origin and Evolution of Hymenopteran Insects (Происхождение и эволюция перепончатокрылых насекомых). – Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, Nauka, 174: 1–191 (In Russian). Rasnitsyn A.P. (Расницын А.П.), 1980b. The subclass Scarabaeona. Winged insects (Подкласс Scarabaeona. Крылатые насекомые). – In: Rohdendorf B.B. & Rasnitsyn A.P., eds (ред. Родендорф Б.Б. и Расницын А.П.), A Historical Development of the Insect Class (Историческое развитие класса насекомых). Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, Nauka, 175: 24–28 (269 p.) (In Russian). Rasnitsyn A.P. (Расницын А.П.), 1986. Inadaptation and euadaptation (Инадаптация и эвадаптация). – Paleontologicheskii zhurnal (Палеонтологический журнал), 1: 3–7. (In Russian). Rasnitsyn A.P. (Расницын А.П.), 1987. The tempo of evolution and evolutionary theory (an adaptive compromise hypothesis) (Темпы эволюции и эволюционная теория (гипотеза адаптивного компромисса)). – In: Tatarinov L.P. & Rasnitsyn A.P., eds (ред. Татаринов Л.П. и Расницын А.П.), Evolution and Biocoenotic Crises (Эволюция и биоценотические кризисы). Moscow, Nauka: 46–63. (In Russian). Redtenbacher J., 1886. Vergleichende Studien über das Flügelgeäder der Insecten. – Ann. Kaiserl.-Königl. Naturwiss. Hofmus., 1: 153–232. Ribera I., Hogan J.E. & Vogler A.P., 2002. Phylogeny of hydradephagan water beetles inferred from 18S rRNA sequences. – Mol. Phyl. Evolution, 23 (1): 43–62. Richter A.A. (Рихтер А.А.), 1935. On the venation of beetle elytra (О жилковании надкрылий жуков). – Russkoe entomologicheskoe obozrenie (Русское энтомологическое обозрение), 26: 25–28. (In Russian). Rohdendorf B.B. (Родендорф Б.Б.), 1949. Evolution and Classification of the Flight Apparatus of Insects (Эволюция и классификация летательного аппарата насекомых). – Proceedings of the Paleontological Institute of the USSR Academy of Sciences (Труды ПИН АН СССР). Moscow, USSR Academy of Sciences Publishers, 16. 176 p. (In Russian). Roughley R.E., 1981. Trachypachidae and Hydradephaga (Coleoptera): A monophyletic unit? – Pan-Pacif. Entomol., 57: 273–285.

REFERENCES

261

Ruhnau S., 1986. Phylogenetic relationships within the Hydradephaga (Coleoptera) using larval and pupal characters. – Entomol. Basil., 11: 231–271. Schmalhausen I.I. (Шмальгаузен И.И.), 1964. Regulation of Form-building in the Course of Individual Development (Регуляция формобразования в индивидуальном развитии). Moscow, Nauka. 136 p. (In Russian). Schmalhausen I.I. (Шмальгаузен И.И.), 1982. The Organism as a Whole in the Course of Individual and Historic Development (Организм как целое в индивидуальном и историческом развитии). Moscow, Nauka. 380 p. (In Russian). Saalas U., 1936. Über das Flügelgeäder und die phylogenetische Entwicklung der Cerambyciden. – Annales Zoologici Societatis Zoologicae-Botanicae Fennicae “Vanamo”, 4 (1): 1–198, 19 pls. Schneider P., 1975. Die Flugtypen der Käfer (Coleoptera). – Entomol. German., 1 (3–4): 222–231. Schneider P., 1978. Die Flug- und Faltungstypen der Käfer (Coleoptera). – Zool. Jb., Anat., 99 (2): 174–210. Schneider P., 1997. Flugverhalten und Stoffwechsel des südafrikanischen Fruchtkäfers Pachnoda sinuata. Heidelberg, Wissenschaftliche Filme aus Heidelberg (n. v.) Schneider P. & Hermes M., 1976. Die Bedeutung der Elytren bei Vertreten des Melolontha-Flugtyps (Coleoptera). – J. Compar. Physiol., A106 (1): 39–49 (after: Гродницкий и Морозов, 1995). Scholtz C.H., Browne D.J. & Kukalovà-Peck J., 1994. Glaresidae, archaeopteryx of the Scarabaeoidea (Coleoptera). – Syst. Entomol., 19: 259–277. Sen Gupta T. & Crowson R.A., 1973. A review of the classification of Cerylonidae (Coleoptera, Clavicornia). – Trans. Roy. Entomol. Soc. London, 124: 365–446. Sharov A.G., 1966. Basic Arthropodan Stock, with Special Reference to Insects. Oxford, Pergamon Press. 271 p. Sharp D., 1882. On aquatic carnivorous Coleoptera, or Dytiscidae. – Trans. Roy. Dublin Soc., 2: 179–1003. Shull V.L., Vogler A.P., Baker M.D., Maddison D.R. & Hammond P.M., 2001. Sequence alignment of 18S ribosomal RNA and the basal relationships of adephagan beetles: Evidence for monophyly of aquatic families and the placement of Trachypachidae. – Syst. Biol., 50 (6): 945–969. Ślipiński S.A. & Lawrence J.F., 1999. Phylogeny and classification of Zopheridae sensu novo (Coleoptera: Tenebrionoidea) with a review of the genera of Zopherinae (excluding Monommatini). – Annales zoologici, Warszawa, 49 (1/2): 1–53. Snodgrass R.E., 1909. The thorax of insects and articulation of the wings. – Proceedings of the United States National Museum, 36: 511–595, pls 40–69. Snodgrass R.E., 1935. Principles of Insect Morphology. New York–London, McGrawHill. 667 p. Snodgrass R.E., 1952. A Textbook of Arthropodan Anatomy. Ithaca, New York. 363 p.

262

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Stibick J.N.L., 1979. Classification of the Elateridae (Coleoptera). Relationships and classification of the subfamilies and tribes. – Pacific Insects, 20: 145–186. Suzuki K., 1970. Comparative morphology and evolution of the hindwings of the Chrysomelidae (Coleoptera). – Kontyû, 38 (3): 257–267. Suzuki K., 1994. Comparative morphology of the hindwing venation of the Chrysomelidae (Coleoptera). – In: Jolivet P.H., Cox M.L. & Petitpierre E., eds, Novel Aspects of the Biology of Chrysomelidae. Dordrecht, etc., Kluwer Academic Publishers: 337–354. Tillyard R.J., 1926. The Insects of Australia and New Zealand. Sydney, Angus & Robertson. 560 p. Vogel S., 1967. Flight in Drosophila. II. Variation in stroke parameters and wing contour. – J. Exp. Biol., 46 (2): 383–392. Wallace F.L. & Fox R.C., 1975. A comparative morphological study of the hind wing venation of the order Coleoptera, Part I. – Proc. Entomol. Soc. Washington, 77 (3): 329–354. Wallace F.L. & Fox R.C., 1980. A comparative morphological study of the hind wing venation of the order Coleoptera, Part II. – Proc. Entomol. Soc. Washington, 82 (4): 609–654. Ward R.D., 1979. Metathoracic wing structures as phylogenetic indicators in the Adephaga. – In: Erwin T.L., Ball G.E., Whitehead D.R. & Halpern A.L., eds, Carabid Beetles: Their Evolution, Natural History, and Classification. Dordrecht, etc., W. Junk: 181–191. Weis-Fogh T., 1973. Quick estimates of flight fitness in hovering animals, including novel mechanisms for lift production. – J. Exp. Biol., 59 (1): 169–230. Weis-Fogh T., 1975. Flapping flight and power in birds and insects, conventional and novel mechanisms. – Swimming and Flying in Nature. New York: 729–762. Wilson J.W. 1930. The genitalia and wing venation of the Cucujidae and related families. – Annals of the Entomological Society of America, 23: 305–358. Wilson S.J., 1934. The anatomy of Chrysochus auratus Fab., Coleoptera: Chrysomelidae, with an extended discussion of the wing venation. – J. N.Y. Entomol. Soc., 42: 65–85. Wootton R.J., 1979. Function, homology and terminology in insect wings. – Syst. Entomol., 4: 81–93. Wootton R.J., 1981. Support and deformability in insect wings. – J. Zool., London, 193: 447–468. Wootton R.J., 1992. Functional morphology of insect wings. – Annu. Rev. Entomol., 37: 113–140. Zherikhin V.V. & Gratshev V.G., 1995. A comparative study of the hind wing venation of the subfamily Curculionoidea, with phylogenetic implications. – In: Pakaluk J. & Ślipiński S.A., eds, Biology, Phylogeny and Classiﬁcation of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Warszawa, Muzeum & Instytut Zoologii PAN: 779–1006.

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APPENDIX 2. A LIST OF COLEOPTERA STUDIED The species measured are marked with an asterisk (*).

Suborder Adephaga Gyrinidae: Gyrinus natator Linnaeus 1758, G. marinus Gyllenhal 1808, Diunetus orientalis (Mooder 1776), Porrorhynchus marginatus Laporte 1835, Orectochilus (Patrus) sp. – Haliplidae: Haliplus ruficollis (DeGeer 1774). – Noteridae: Noterinae: Noterus crassicornis (O.F. Müller 1776), Neohydrocoptus sp., Canthydrus sp., Hydrocanthus indicus Wehncke 1876. – Amphizoidae: *Amphizoa lecontei Mattews 1872. – Hygrobiidae: *Hygrobia hermanni (Fabricius 1775). – Dytiscidae: Dytiscinae: Acilius sulcatus (Linnaeus 1758), *A. canaliculatus (Nicolai 1822), *Graphoderus cinereus (Linnaeus 1758), G. zonatus (Hoppe 1795), Eretes sticticus (Linnaeus 1767), *Hydaticus seminiger (DeGeer 1774), *Dytiscus circumcinctus Ahrens 1811; Colymbetinae: *Colymbetes paykulli Erichson 1837, Rhantus frontalis (Marsham 1802), *Rh. exsoletus (Forster 1771); Agabinae: Agabus undulatus (Schrank 1776), *A. sturmii (Gyllenhal 1808), *A. unguicularis (C.G. Thomson 1867), *Ilybius ater (DeGeer 1774); Copelatinae: Copelatus sp.; Laccophilinae: *Laccophilus minutus (Linnaeus 1758), L. chinensis Bohemann 1858, Neptosternus sp.; Hydroporinae: *Hydroporus rufifrons (O.F. Müller 1776), *Suphrodytes dorsalis (Fabricius 1777), Stictotarsus multilineatus (Falkenström 1922), *Hygrotus impressopunctatus (Schaller 1783), *H. decoratus (Gyllenhal 1810), *H. inaequalis (Fabricius 1776), *Porhydrus lineatus (Fabricius 1775), *Hydroglyphus geminus (Fabricius 1792), *Hyphydrus ovatus (Linnaeus 1761), Hyphydrus lyratus lyratus Swartz 1808. – Rhysodidae: Rhysodes sulcatus (Fabricius 1787), Omoglymmius germari (Ganglbauer 1892). – Trachypachidae: Trachypachus zetterstedti (Gyllenhal 1827), Systolosoma breve Solier 1849. – Carabidae: Apotominae: *Apotomus rufithorax Pecchioli 1838; Siagoninae: *Siagona europaea Dejean 1826; Carabinae: Carabus granulatus Linnaeus 1758, *Calosoma cyanescens Motschulsky 1859, *C. chinense Kirby 1817, Cicindela campestris Linnaeus 1758, *C. hybrida Linnaeus 1758, Megacephala euphratica armenica Laporte 1834, Neocollyris bonellii (Guérin-Méneville 1833), *Omoph-

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ron limbatum (Fabricius 1776), O. aequale A. Morawitz 1863, O. rotundatum Chaudoir 1852, *Paropisthius davidis (Fairmaire 1887), Leistus terminatus (Panzer 1793, *Nebria (Paranebria) livida Linnaeus 1758, N. (Boreonebria) nivalis (Paykull 1798), *N. (Boreonebria) rufescens (Ström 1768), Pelophila borealis (Paykull 1790), Notiophilus impressifrons A. Morawitz 1862, N. biguttatus (Fabricius 1779), Loricera pilicornis (Fabricius 1775); Pseudomorphinae: Sphallomorpha sp.; Elaphrinae: *Pachyteles sp., Eustra matanga matanga Andrewes 1919, Pseudozaena orientalis (Klug 1831), *Platyrrhopalopsis picteti (Westwood 1874), Stichonotus leai Sloan 1910, *Eucamaragnatus angulicollis Jeannel 1937, *Elaphrus cupreus Duftschmid 1812, *Broscus cephalotes (Linnaeus 1758), Miscodera arctica (Paykull 1798), Scarites terricola Bonelli 1813, *Clivina ypsilon Dejean 1829, Coryza carinifrons Reitter 1900, *Sparostes striatulus Putzeys 1866, Ardistomis sp., Oxydrepanus sp., Dyschirius arenosus Stephens 1827, *Dyschiriodes nitidus (Dejean 1825), Cymbionotum semelederi (Chaudoir 1861), Melaenus elegans Dejean 1831; Trechinae: Diplous depressus (Gebler 1829), Patrobus septentrionis Dejean 1828, Pogonus luridipennis (Germar 1822), *Paratachys turkestanicus Csiki 1928, *Asaphidion cupreum Andrewes 1925, Bembidion (Euperyphus) combustum Mènètriès 1832, B. (Bracteon) litorale (Olivier 1790), Trechus quadristriatus (Schrank 1781), *Perileptus japonicus H. Bates 1873, *Blemus discus (Fabricius 1792), *Gehringia olympica Darlington 1933, Mecyclothorax ambiguus (Erichson 1842); Harpalinae: *Amara nitida Sturm 1825, Zabrus morio Mènètriès 1832, Curtonotus dauricus (Motschulsky 1844), *Platynus assimilis (Paykull 1790), Agonum (s.str.) impressum (Panzer 1797), Calathus ambiguus (Paykull 1790), Chlaenius vestitus (Paykull 1790), Panagaeus cruxmajor (Linnaeus 1758), Badister meridionalis Puel 1925, Oodes helopioides (Fabricius 1792), Pterostichus (Platysma) niger (Schaller 1783), P. (Melanius) nigrita (Paykull 1790), Poecilus cupreus (Linnaeus 1758), Pareuryaptus adoxus (Tschitschérine 1899), Morion guineensis Immhoff 1843, Anisodactylus binotatus (Fabricius 1787), Dicheirotrichus placidus (Gyllenhal 1827, Stenolophus discophorus (Fischer-Waldheim 1823), Harpalus affinis (Schrank 1781), Ophonus nitidulus Stephens 1828, Dixus semicylindricus Piochard de la Brûlerie 1872, Trichotichnus nishioi Habu 1961, Amblystomus metallescens (Dejean 1829), *Odacantha melanura (Linnaeus 1767), Cymindis binotata (Fischer-Waldheim 1820), Cymindoidea famini (Dejean 1826), Orthogonius sp., Zuphium olens (Rossi 1790), *Galerita sp., *Tetragonoderus intermedius Solsky 1874, Lebia bifenestrata A. Morawitz 1862, Lebia cruxminor (Linnaeus 1758), *Microlestes corticalis (Dufour 1820), Mormolyce phyllodes borneensis Gestro 1875; Brachininae: *Pheropsophus jessoensis A. Morawitz 1862, *Brachinus brevicollis Motschulsky 1844, B. chinensis Chaudoir 1850, Styphlomerus sp., Mastax thermarum (Steven 1806).

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325

Suborder Myxophaga Sphaeriusidae: Sphaerius acaroides Waltl 1838 Suborder Archostemata Cupedidae: Tenomerga mucida (Chevrolat 1844), Priacma serrata (LeConte 1861). – Micromalthidae: Micromalthus debilis LeConte 1878. – Sikhotealiniidae: Sikhotealinia zhiltzovae Lafer 1996. Suborder Polyphaga Series Eucinetiformia Superfamilia Scirtoidea Eucinetidae: Eucinetus haemorrhoidalis (Germar 1818). – Decliniidae: Declinia relicta Nikitsky et al. 1989. – Scirtidae: Scirtes hemisphaericus (Linnaeus 1767), Scirtes sp., Prionocyphon sp., Cyphon variabilis (Thunberg 1787), Elodes pseudominuta Klausnitzer 1971, Microcara (Linnaeus 1767). – Clambidae: Clambus sp., Acalyptomerus sp. Series Staphyliniformia Superfamilia Hydrophiloidea Helophoridae: *Helophorus sp. – Georissidae: *Georissus sp. – Hydrochidae: *Hydrochus elongatus (Schaller 1783) Spercheidae: Spercheus emarginatus (Schaller 1783). – Hydrophilidae: Hydrophilinae: *Hydrochara caraboides (Linnaeus 1758), *Hydrophilus aterrimus Eschscholtz 1822, *Hydrobius fuscipes (Linnaeus 1758), Enochrus quadripunctatus (Herbst 1797), *Anacaena lutescens (Stephens 1829), *Berosus (s.str.) signaticollis (Charpentier 1825), B. (s.str.) luridus (Linnaeus 1761), B. (Enoplurus) sp.; Spaeridiinae: *Coelostoma orbiculare (Fabricius 1775), Cercyon convexiusculum (Stephens 1829), Sphaeridium scarabaeoides (Linnaeus 1758). – Sphaeritidae: *Sphaerites glabratus (Fabricius 1792). – Synteliidae: *Syntelia histeroides Lewis 1882. – Histeridae: Saprininae: *Saprinus semipunctatus (Fabricius 1798); Histerinae: *Hister quadrinotatus Scriba 1790, H. unicolor Linnaeus 1758, *Margarinotus striola (C. Sahlberg 1834), Pachylister inaequalis (Olivier 1789), Hololepta plana (Sulzer 1776).

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Superfamilia Scarabaeoidea Trogidae: *Trox hispidus (Pontoppidan 1763). – Bolboceratidae: *Odonteus armiger (Scopoli 1772). – Glaresidae: *Glaresis beckeri Solsky 1870. – Lucanidae: Lucaninae: *Prismognatus subaeneus Motschulsky 1860, Platycerus caraboides (Linnaeus 1758); Syndesinae: *Sinodendron cylindricum (Linnaeus 1758), Ceruchus chrysomelinus (Hochenwarth 1785). – Passalidae: Passalinae: Leptaulax dentatus (Fabricius 1792), *Leptaulax sp., Aceraius sp.; Aulacocyclinae: Ceracupes fronticornis (Westwood 1842). – Glaphyridae: Glaphyrus micans Faldermann 1835, Amphicoma (Pygopleurus) vulpes (Fabricius 1781). – Ochodaeidae: Codocera ferruginea (Eschscholtz 1818). – Geotrupidae: *Anoplotrupes stercorosus (Hartmann in Scriba 1791). – Ceratocanthidae: Madrasostes sp., Pterorthochaedes sp. – Hybosoridae: Hybosorus illigeri (Reiche 1853), Phaeochroops sp., Phaeochrous sp. – Scarabaeidae: Aphodiinae: *Aphodius rufipes (Linnaeus 1758), *A. ater (DeGeer 1774), Aegialia sabuleti (Panzer 1797); Scarabaeinae: Scarabaeus pius (Illiger 1803), *Oniticellus pallipes (Fabricius 1781), Onthophagus taurus (Schreber 1759), Sisyphus shaefferi (Linnaeus 1758), Copris lunaris (Linnaeus 1758), C. ochus Motschulsky 1860; Hopliinae: Hoplia parvula Krynicki 1832; Sericinae: Serica brunnea (Linnaeus 1758); Euchirinae: Cheirotonus macleayi formosanus Ohaus 1913; Melolonthinae: *Polyphylla alba (Pallas 1773), Amphimallon solstitialis (Linnaeus 1758), Melolontha hippocastani Fabricius 1801; Dynastinae: Pentodon idiota (Herbst 1789); Rutelinae: *Blitopertha pallidipennis (Reitter 1903); Cetoniinae: *Lasiotrichius succinctus (Pallas 1781), Gnorimus subopacus (Motschulsky 1860), Cetonia aurata (Linnaeus 1761), C. magnifica Ballion 1870, *Netocia metallica (Herbst 1782), Valgus hemipterus (Linnaeus 1758). Superfamilia Staphylinoidea Ptiliidae: Acrotrichis montandonii (Allibert 1844). – Hydraenidae: Hydraeninae: Ochthebius sp.; Limnebiinae: Limnebius sp. – Agyrtidae: Pteroloma sibiricum Szèkessy 1935, Agyrtes castaneus (Fabricius 1792). – Leiodidae: Leiodinae: Agathidium sp., Anisotoma glabra (Kugelann 1794, Amphicyllis globus (Fabricius 1792), Colenis sp., Leiodes oblongus (Erichson 1845), Leiodes sp.; Cholevinae: Cholevinus fuscipes (Ménétriés 1849), Sciodrepoides fumatus (Spence 1815). – Silphidae: Silphinae: Silpha obscura Linnaeus 1758, Necrodes littoralis (Linnaeus 1758), Thanatophilus lapponicus (Herbst 1793); Nicrophorinae: Nicrophorus vespillo (Linnaeus 1758), N. tenuipes Lewis 1887, Ptomascopus morio Kraatz 1877. – Scydmaenidae: Scydmaenus sp. – Staphylinidae: Omaliinae: Eusphalerum anale (Erichson 1840); Pselaphinae: Rybaxis longicornis (Leach 1817); Tachyporinae: Tachinus sp., Sepedophilus sp.; Oxytelinae: Bledius sp.; Oxyporinae: Oxyporus maxillosus Fabricius 1792; Steninae: Stenus sp.; Staphylininae:

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Staphylinus pubescens DeGeer 1874, Philonthus sp.; Scaphidiinae: Scaphisoma inopinatum Löbl 1967, Scaphidium quadrimaculatum Olivier 1790. Series Elateriformia Superfamilia Elateroidea Artematopodidae: Macropogon pubescens Motschulsky 1860. – Brachypsectridae: Brachypsectra fulva LeConte 1874. – Cerophytidae: Cerophytum elateroides Latreille 1809. – Elateridae: Lissominae: Drapetes mordelloides (Host 1789); Cebrioninae: Cebrio sp.; Oxynopterinae: Campsosternus sp., Pectocera fortunei Candèze 1873; Agrypninae: Danosoma fasciata (Linnaeus 1758), Agrypnus murinus (Linnaeus 1758), Agrypnus sp.1 and 2, Rismethus sp., Cryptalaus sordidus (Westwood 1848), Lacon sp.1 and 2, Tetrigus flabellatus (Germar 1844), Drasterius bimaculatus P. Rossi 1790, Aeoloides sp., Aeoloderma sp.1 and 2; Elaterinae: Ludigenus politus Candèze 1863, Ampedus pomorum (Herbst 1784), Agriotes sputator (Linnaeus 1758), Melanotus castanipes (Paykull 1800); Dendrometrinae: Denticollis linearis (Linnaeus 1758), Hemicrepidius niger (Linnaeus 1758), Ctenicera cuprea (Fabricius 1775), C. pectinicornis (Linnaeus 1758), Prosternon tesselatum (Linnaeus 1758), Selatosomus latus (Fabricius 1801), S. melancholicus (Fabricius 1798), Eanus costalis (Paykull 1800), Ligmargus depressus (Gebler 1847), Penia sp., Senodonia sp.; Negastriinae: Oedostethus sp., Zorochros sp., Tropihypnus bimargo Reitter 1896; Cardiophorinae: Dicronychus cinereus (Herbst 1784). – Eucnemidae: Phyllocerinae: Phyllocerus elateroides Ménétriés 1832; Melasinae: Otho sphondyloides (Germar 1818), Gen. sp., Melasis buprestoides (Linnaeus 1761); Eucneminae: Eucnemis capucina Ahrens 1812. – Throscidae: Trixagus dermestoides (Linnaeus 1767), Potergus filiformis Bonvouloir 1870. – Omalisidae: Omalisus fontisbellaquei Geoffroy 1785. – Drilidae: Drilus concolor Ahrens 1812. – Lycidae: Erotinae: Platycis minutus (Fabricius 1787); Calochrominae: Lygistopterus sanguineus (Linnaeus 1758). – Lampyridae: Lampyrinae: Lampyris noctiluca (Linnaeus 1767); Luciolinae: Luciola mingrelica Motschulsky 1845. – Omethidae: Drilonius sp. – Cantharidae: Cantharinae: Rhagonycha sp., Cantharis fusca Linnaeus 1758; Malthininae: Malthinus sp. Superfamilia Byrrhoidea Eulichadidae: Eulichas pacholatkoi Jäch 1995, Eulichas sp. – Callirhipidae: Callirhipis sp. – Ptilodactylidae: Gen.1 sp., Gen.2 sp. – Chelonariidae: Chelonarium sp., Pseudochelonarium sp. – Psephenidae: Psephenoidinae: Psephenoides sp.; Eubriinae: Eubria palustris (Germar 1818). – Elmidae: Elminae: Grouvellinus rioloides (Reitter 1887), Graphelmis sp.; Larainae: Potamodytes sp. – Dryopidae: Parahelichus angulicollis (Reitter 1887), Helichus

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granulosus Deleve 1974, Dryops auriculatus (Geoffroy 1785). – Limnichidae: Limnichinae: Limnichus sp., Byrrhinus subregularis Pic 1923, Mandersia sp. – Heteroceridae: Heterocerus sp. – Byrrhidae: Byrrhinae: Byrrhus sp., Morychus rutilans (Motschulsky 1845), Arctobyrrhus dovrensis Münster 1902; Syncalyptinae: Syncalypta sp. Superfamilia Buprestoidea Buprestidae: Schizopodinae: Glyptoscelimorpha sp., Schizopus laetus LeConte 1858; Julodinae: Julodis variolaris (Pallas 1773); Buprestinae: Dicerca sp., Buprestis sp., Capnodis tenebrionis (Linnaeus 1758), Chrysobothris affinis (Fabricius 1794), Anthaxia nigrojubata Roubal 1913, Anthaxia nitidula (Linnaeus 1758); Agrilinae: Agrilus sp. Superfamilia Dascilloidea Dascillidae: Dascillus cervinus (Linnaeus 1758). – Rhipiceridae: Rhipicera sp., Arrhaphipterus phlomidis K. Daniel 1900, A. schelkownikoffi Reitter 1893. Series Bostrichiformia Superfamilia Bostrichoidea Dermestidae: Dermestinae: Dermestes laniarius Illiger 1801, D. leopardinus Mulsant et Godart 1855; Orphilinae: Orphilus niger (P. Rossi 1790); Attageninae: Attagenus megatoma Fabricius 1798, A. unicolor (Brahm 1790); Megatominae: Megatoma undata (Linnaeus 1758), Anthrenus verbasci (Linnaeus 1767). – Nosodendridae: Nosodendron asiaticum Lewis 1889. – Anobiidae: Eucradinae: Hedobia pubescens (Olivier 1790); Ptininae: Ptinus sp.; Ernobiinae: Xestobium rufovillosum (DeGeer 1774); Anobiinae: Stegobium paniceum (Linnaeus 1758), Oligomerus retowskii Schilsky 1898, O. brunneus (Olivier 1790), Hadrobregmus pertinax (Linnaeus 1758), Priobium carpini (Herbst 1793); Ptilininae: Ptilinus pectinicornis (Linnaeus 1758); Xyletininae: Xyletinus ornatus Germar 1842; Dorcatominae: Mizodorcatoma sibirica Reitter 1879. – Endecatomidae: Endecatomus lanatus Lesne 1934. – Bostrichidae: Bostrichinae: Bostrichus capucinus (Linnaeus 1758), Amphicerus bimaculata (Olivier 1790), Lichenophanes varius (Illiger 1801), Sinoxylon sp.; Psoinae: Psoa dubia (P. Rossi 1792); Lyctinae: Lyctus suturalis Faldermann 1837, Tristaria sp. Superfamilia Derodontoidea Derodontidae: Peltasticinae: Peltastica amurensis Reitter 1879; Laricobiinae: Laricobius kovalevi Nikitsky 1992; Derodontinae: Derodontus longiclavis Nikitsky 1987. – Jacobsoniidae: Sarothrias crowsoni Löbl et Burckhardt 1988

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Series Cucujiformia Superfamilia Lymexyloidea Lymexilidae: Hylecoetinae: Elateroides dermestoides (Linnaeus 1761); Lymexilinae: Atractocerus sp1 and 2.; Melittommatinae: Melittomma sp. Superfamilia Tenebrionoidea Stenotrachelidae: Stenotrachelinae: *Scotodes annulatus Eschscholtz 1818, *Stenotrachelus aeneus (Fabricius 1787); Nematoplinae: Nematoplus semenovi Nikitsky 1973; Cephaloinae: Cephaloon pallens (Motschulsky 1860). – Mordellidae: *Variimorda villosa (Schrank 1781), Tomoxia bucephala Costa 1854, Mordellistena humeralis (Linnaeus 1758). – Rhipiphoridae: Pelecotominae: Pelecotoma fennica (Paykull 1799); Ptilophorinae: *Ptilophorus dufouri (Latreille 1817); Rhipiphorinae: Macrosiagon tricuspidatum (Lepechin 1774). – Melandryidae: Melandryinae: *Serropalpus barbatus (Schaller 1783), *Melandrya caraboides (Linnaeus 1760), M. dubia (Schaller 1783), Phloiotrya sp., Dircaea quadriguttata (Paykull 1798), Xylita laevigata (Hellenius 1786), Orchesia micans (Panzer 1794), Hypulus quercinus (Quensel 1790), Abdera flexuosa (Paykull 1799); Osphyinae: *Osphya bipunctata (Fabricius 1775). – Synchroidae: *Synchroa melanotoides Lewis 1895, Synchroa sp. – Oedemeridae: Calopodinae: *Calopus serraticornis (Linnaeus 1758); Oedemerinae: Ditylus laevis (Fabricius 1792), *Oedemera virescens (Linnaeus 1767), *Ischnomera abdominalis (Heyden 1887). – Tetratomidae: Tetratominae: *Tetratoma sp.; Penthinae: *Penthe pimelia (Fabricius 1801); Hallomeninae:Hallomenus binotatus (Quensel 1790), *Mycetoma suturale (Panzer 1797); Eustrophinae: Synstrophus sp. – Archeocrypticidae: Archeocrypticus patagonicus Kaszab 1964, Sivacrypticus sp. – Mycetophagidae: *Mycetophagus quadripustulatus (Linnaeus 1761), M. piceus (Fabricius 1777), Litargus connexus (Fourcroy 1785). – Ciidae: Ciinae: Cis boleti (Scopoli 1763), Cis sp., Xylographus sp. – Boridae: *Boros schneideri (Panzer 1795). – Ulodidae: Ulodes verrucosus Erichson 1842. – Zopheridae: Colydiinae: Colobicus sp.1 and 2, *Colydium elongatum (Fabricius 1787), *Bitoma crenata (Fabricius 1775); Zopherinae: *Pycnomerus sulcicollis (Germar 1824), *Monomma sp. – Prostomidae: *Prostomis mandibularis (Fabricius 1801). – Tenebrionidae: Lagriinae: *Lagria hirta (Linnaeus 1758), Gen. sp., Cossyphus tauricus Steven 1829, Cossyphus sp., Belopus procerus (Mulsant 1854); Tenebrioninae: *Tenebrio molitor Linnaeus 1758, T. obscurus (Fabricius 1792), *Bolitophagus reticulatus (Linnaeus 1767), Eledona agaricola (Herbst 1783), Rhipidandrus sp., Cryphaeus cornutus (FischerWaldheim 1844), Cryphaeus sp., *Campsiomorpha regia (Fairmaire 1903); Alleculinae: *Omophlus flavipennis Küster 1850, Mycetochara flavipes (Fabricius 1792), Gonodera macrophtalma Reitter 1884; Diaperinae: Scaphidema metallicum (Fabricius 1792), *Diaperis boleti (Linnaeus 1758), Pentaphyllus sp.1–3,

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Myrmechixenus subterraneus Chevrolat 1835, Leiochrodes sp.; Coelometopinae: Catapiestus sp. – Trictenotomidae: Trictenotoma sp. – Pythidae: *Pytho depresus (Linnaeus 1767). – Salpingidae: Salpinginae: *Salpingus ruficollis (Linnaeus 1761), Rabocerus foveolatus (Ljungh 1823), Sphaeriestes bimaculatus (Gyllenhal 1810), Istrisia rufobrunnea Lewis 1895; Inopeplinae: Inopeplus sp., ?Inopeplus sp.; Prostominiinae: Prostominia lewisi Reitter 1889; Othniinae: *Elacatis kraatzi (Reitter 1879). – Pterogeniidae: *Histanocerus wallacei Burckhardt et Löbl 1992. – Pyrochroidae: Pedilinae: *Pedilus polyxanthus Semenov 1900; Pyrochroinae: Pyrochroa coccinea (Linnaeus 1761), Schizotus fuscicollis (Mannerheim 1852), Pseudopyrochroa sp. – Mycteridae: *Mycterus tibialis Küster 1850, M. articulatus (Reitter 1911). – Anthicidae: Eurygeniinae: Stereopalpus centroasiaticus (Semenov 1893); Steropinae: *Steropes caspius Steven 1806; Macratriinae: Macratria sp.; Ischaliinae: *Ischalia sp.; Anthicinae: Omonadus floralis (Linnaeus 1758), *Notoxus monoceros (Linnaeus 1760). – Meloidae: Gen. sp., *Lytta sp., *Mylabris sp.1 and 2, *Zonitis sp. – Aderidae: *Aderus populneus (Creutzer 1796), Anidorus nigrinus (Germar 1831), Phytobaenus amabilis F. Sahlberg 1834. – Scraptiidae: *Gen.sp. – Anaspididae: *Anaspis thoracica (Linnaeus 1758), A. marginicollis Lindberg 1925, Anaspis sp.1 and 2. Superfamilia Cucujoidea Protocucujidae: Ericmodes fuscitarsis (Reitter 1878). – Sphindidae: Odontosphindinae: Odontosphindus grandis (Hampe 1861), Sphindus brevis Reitter 1879, S. dubius (Gyllenhal 1808), Aspidiphorus sp. – Byturidae: Byturinae: Byturus tomentosus (DeGeer 1774), B. ochraceus (Scriba 1790). – Biphyllidae: Biphyllus lunatus (Fabricius 1787) Silvanidae: Brontinae: Dendrophagus crenatus (Paykull 1799), Ulejota planatus (Linnaeus 1761); Silvaninae: Silvanus unidentatus (Olivier 1790), Psammoecus bipunctatus (Fabricius 1792). – Passandridae: Passandra sp. – Cucujidae: Cucujus haematodes Erichson 1845. – Laemophloeidae: Laemophloeus submonilis Reitter 1889, L. muticus (Fabricius 1781). – Propalticidae: Propalticus sp. – Phloeostichidae: Phloeostichus denticollis W. Redtenbacher 1842. – Cryptophagidae: Cryptophaginae: Antherophagus nigricornis (Fabricius 1787), Cryptophagus sp., Telmatophilus typhae (Fallén 1802); Atomariinae: Anchicera apicalis Erichson 1846. – Monotomidae: Rhizophaginae: Rhizophagus ussuriensis Nikitsky 1984, Rh. dispar (Paykull 1800); Monotominae: Shoguna sp. – Nitidulidae: Nitidulinae: Cychramus variegatus (Herbst 1792), Soronia punctatissima (Illiger 1794), Ipidia binotata Reitter 1875; Cryptarchinae: Pityophagus ferrugineus (Linnaeus 1761), Glischrochilus pantherinus Reitter 1879, G. quadripunctatus (Linnaeus 1758). – Brachypteridae: Brachypterus urticae (Fabricius 1792). – Helotidae: Helota fulviventris Kolbe 1886. – Phalacridae: Tolyphus bimaculatus L. Medvedev 1963,

APPENDIX 2

331

Olibrus bicolor (Fabricius 1792), Olibrus sp., Phalacrus sp. – Languriidae: Xenoscelinae: Leucohimatium langii (Solsky 1866), Macrophagus robustus Motschulsky 1845; Languriinae: Anadastus menetriesii Motschulsky 1860, Gen. sp.; Cryptophilinae: Cryptophilus sp. – Erotylidae: Dacninae: Dacne bipustulata (Thunberg 1781); Megalodacninae: Episcapha morawitzi Solsky 1871; Tritominae: Tritoma bipustulata Fabricius 1775; Triplax aenea (Schaller 1783). – Bothrideridae: Bothriderinae: Bothrideres contractus (Geoffroy 1785), Dastarcus sp. – Cerylonidae: Ceryloninae: Cerylon histeroides (Fabricius 1792). – Endomychidae: Lycoperdininae: Mycetina apicalis Motschulsky 1835, Gen. sp.; Endomychinae: Endomychus armeniacus Motschulsky 1835; Pleganophorinae: Pleganophorus sp.; Anamorphinae: Dexialia minor M. Chûjô 1941. – Coccinelidae: Scymninae: Scymnus haemorrhoidalis Herbst 1797; Coccidulinae: Coccidula rufa (Herbst 1783); Coccinellinae: Aiolocaria hexaspilota (Hope 1831), Coccinella septempunctata Linnaeus 1758, Ceratomegilla notata (Laicharting 1781). – Corylophidae: Corylophinae: Orthoperus sp.; Parmulinae: Sacium sp. – Lathridiidae: Lathridiinae: Stephostethus lardarius (DeGeer 1775); Corticariinae: Corticaria pubescens (Gyllenhal 1827). – Discolomatidae: Aphanocephalinae: Aphanocephalus sp. Superfamilia Cleroidea Trogossitidae: Peltinae: Ostoma ferruginea (Linnaeus 1758), Peltis grossa (Linnaeus 1758), Thymalus subtilis Reitter 1889; Lophocaterinae: Grynocharis oblonga (Linnaeus 1758); Trogossitinae: Temnoscheila japonica Reitter 1875, Leperina squamulata Gebler 1830, Tenebrioides mauritanicus (Linnaeus 1758). – Cleridae: Tillinae: Tillus elongatus (Linnaeus 1758); Clerinae: Trichodes ircutensis Laxmann 1770, T. apiarius (Linnaeus 1758), Clerus mutillarius Fabricius 1775, Thanasimus formicarius (Linnaeus 1758); Enopliinae: Dermestoides sanguinicollis (Fabricius 1787), Tenerus sp., Korynetinae: Korynetes coeruleus (DeGeer 1775). – Prionoceridae: Prionocerus sp. – Melyridae: Melyrinae, Cerallus sp.; Rhadalinae: Semijulistus spectabilis (Lewis 1895); Dasytinae: Enicopus pilosus Scopoli 1763, Danacaea sp., Dasytes sp.; Malachiinae: Malachius bipustulatus (Linnaeus 1758). Superfamilia Chrysomeloidea Cerambycidae: Lepturinae: Oxymirus cursor (Linnaeus 1758), Pachyta quadrimaculata (Linnaeus 1758), Rhagium inquisitor (Linnaeus 1758), Brachyta interrogationis (Linnaeus 1758), Corymbia rubra (Linnaeus 1758), Leptura quadrifasciata (Linnaeus 1758), Strangalia attenuata (Linnaeus 1758); Cerambycinae: Aromia moschata (Linnaeus 1758), Xylotrechus rusticus (Linnaeus 1758), Molorchus minor (Linnaeus 1767), Necydalis major Linnaeus 1758; Prioninae: Prionus coriarius (Linnaeus 1758); Lamiinae: Agapanthea violacea (Fabricius 1775), Acanthocinus aedilis (Linnaeus 1758). – Megalopodidae: Zeugophorinae: Zeu-

332

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

gophora subspinosa (Fabricius 1781). – Orsodacnidae: Orsodacninae: Orsodacne cerasi (Linnaeus 1758); Aulacoscelidinae: Janbechynea paradoxa Monrós 1953. – Chrysomelidae: Sagrinae: Sagra femorata (Drury 1773); Bruchinae: Bruchidius orchesioides (Heyden 1892); Donaciinae: Donacia sp.; Criocerinae: Lilioceris sp.; Hispinae: Aspidimorpha difformis (Motschulsky 1860), Cassida rubiginosa O.F. Müller 1776; Chrysomelinae: Chrysomela sp., Leptinotarsa decemlineata (Say 1824); Galerucinae: Galerucella lineola (Fabricius 1781); Cryptocephalinae: Cryptocephalus octopunctatus (Scopoli 1763), Fulcidax cupreus (Klug 1824), Gen. sp.; Eumolpinae: Adoxus obscurus (Linnaeus 1758), Gen. sp. Superfamilia Curculionoidea Belidae: Belinae: Dicordylus marmoratus (Philippi 1859), Atractuchus annulifer (Philippi 1859), Homalocerus lyciformis (Germar 1833), Belus tibialis Blackburn 1893. – Nemonychidae: Nemonychinae: Nemonyx lepturoides (Fabricius 1801); Doydirhynchinae: Cimberis attelaboides (Fabricius 1787). – Urodontidae: Bruchela suturalis (Fabricius 1792). – Anthribidae: Anthribinae: Platyrhinus resinosus (Scopoli 1763), Platystomos albinus (Linnaeus 1758). – Attelabidae: Rhynchitinae: Rhynchites auratus (Scopoli 1763); Attelabinae: Attelabus nitens (Scopoli 1763); Apoderinae: Apoderus coryli (Linnaeus 1758). – Brentidae: Apioninae: Oxystoma pomonae (Fabricius 1798); Brentinae: Baryrhynchus sp. – Ithyceridae: Ithycerus noveboracensis (Forster 1771). – Brachyceridae: Rhynchophorinae: Sphenophorus abbreviatus (Fabricius 1787).– Barididae: Baridinae: Baris carbonaria (Boheman 1836); Ceutorhynchinae: Mononychus punctumalbum (Herbst 1784). – Curculionidae: Curculioninae: Curculio venosus (Gravenhorst 1807); Cleoninae: Lixus iridis Olivier 1807; Hyperinae: Chlorophanus viridis (Linnaeus 1758); Scolytinae: Tripodendron signatum (Fabricius 1792), Hylastes cunicularius Erichson 1836; Platypodinae: Gen. sp.

APPENDIX 3

333

APPENDIX 3. Table of measurements: BL, body length; WL, total wing length, ML, length of apical membrane. Species Calosoma ch Calosoma cy Broscus Galerita Pheropsophus Sparostes Nebria li Cicindela hy Paropisthius Siagona Nebria ru Platynus Platyrhopalopsis Eucamaragnatus Brachinus Elaphrus Amara Pachyteles Odacantha Omophron Asaphidion Clivina Tetragonoderus Blemus Dyschiriodes Apotomus Microlestes

BL, mm 30.5 21 20 19 17 17 16.5 15.4 11.3 11.1 11.1 10.9 10.8 10.6 9.1 8.6 8.5 7.3 7.1 6.7 6.5 5.6 5.6 5.1 5 4.2 2.7

WL, mm ML, mm Carabidae 33 14.2 19.5 7.6 14.8 5.5 17.4 6.5 17.6 8.2 16.3 7.7 17 7.2 13.7 5.8 11.2 5.16 8.5 3.25 11.1 4.95 7.9 3 14.1 6.85 9.8 4.2 8.4 3.6 8 3.5 6.4 2.3 7.2 3.23 5.5 2.45 9.4 4.96 5.5 2.8 6 3.05 5 2.4 4.9 2.63 4.9 2.7 3.9 2.15 2.68 1.5

WL/BL,% ML/WL,% 108.2 92.9 74 91.6 103.5 95.9 103 89 99.1 76.6 100 72.5 130.6 92.5 92.3 93 75.3 98.6 77.5 140.3 84.6 107.1 89.3 96.1 98 92.9 99.1

43 39 37.2 37.4 46.6 47.2 42.4 42.3 46.1 38.2 44.6 38 48.6 42.9 42.9 43.8 35.9 44.9 44.5 52.8 50.9 50.8 48 53.6 55.1 55.1 56.1

334

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Species Perileptus Paratachys Gehringia

BL, mm 2.7 2.3 1.6

Dytiscus Colymbetes Acilius ca Graphoderus Hydaticus Amphizoa Ilybius Hygrobia Rhantus ex Agabus st Agabus un Hygrotus im Laccophilus Hydroporus Suphrodytes Hyphydrus ov Porhydrus Hygrotus in Hygrotus de Hydroglyphus

34 19.5 17 15.5 14.1 13.2 13.2 10.4 10.2 8.6 7 5.2 5.1 4.9 4.9 4.7 3.5 3.2 2.5 1.97

Hydrophilus Hydrochara Syntelia Saprinus Hister qu Margarinotus Berosus Hydrobius Sphaerites Coelostoma Hydrochus Anacaena Helophorus Cercyon conv

36 19.2 13.5 7.8 6.9 6.9 6.4 6.4 6.3 4 3.9 2.8 2.7 2.5

WL, mm ML, mm 2.95 1.71 2.6 1.55 1.83 1.08 Dytiscoidea 34.5 13.5 18.7 7.8 17 6.8 16.1 5.9 15.6 6 14.2 3.65 16.1 6.4 12 5.7 11.1 4.8 9.1 3.6 6.85 2.5 6.6 3.15 5.9 2.6 5.8 2.84 5.6 2.4 5.1 2.2 4.2 2.1 4.05 2 3.2 1.46 2.35 1.18 Hydrophiloidea 37 10.2 18.4 6.64 12.5 6.93 7.5 4.85 9.8 7.36 8.9 6.75 8.2 3.7 8.35 3.6 7.9 4.3 6 3.5 4.5 2.55 3.8 2 3.25 1.78 3.5 1.95

WL/BL,% ML/WL,% 109.3 58 113 59.6 114.1 58.9 101.5 95.9 100 103.9 110.6 107.6 122 115.4 108.8 105.8 97.9 126.9 115.7 118.4 114.3 108.5 120 126.6 128 119.3

39.1 41.7 40 36.6 38.5 25.7 39.8 47.5 43.2 39.6 36.5 47.7 44.1 49 42.9 43.1 50 49.4 45.6 50

102.8 95.8 92.6 96.2 142 129 128.1 130.5 125 150 115.4 135.7 120.3 140

27.6 36.1 55.4 65.7 75.1 75.8 45.1 43 54.4 58.3 56.7 52.6 54.6 55.7

APPENDIX 3

Species Georissus

BL, mm 2

Prismognatus Polyphylla Leptaulax Netocia Anoplotrupes Sinodendron Aphodius ru Lasiotrichius Blitopertha Oniticellus Trox Odonteus 2 Odonteus 1 Aphodius at Glaresis

31 30 26 18.5 16.5 14 11.5 11.4 11 9.5 8.5 8.4 7.3 5.7 5.25

Campsiomorpha Calopus Mylabris Serropalpus Stenotrachelus Lytta Tenebrio Melandrya Boros Penthe Zonitis Pytho Scotodes Oedemera Synchroa Schizotus Ptilophorus Variimorda Ischnomera Lagria Omophlus

32 19 18.5 17 17 14.4 14 14 12.5 12 12 11 10 10 10 9 9 8.5 8.3 8.3 8

WL, mm ML, mm 5 3.45 Scarabaeoidea 25 10.5 28.7 11.5 24.2 8.3 19.5 9 16.7 5.95 16.05 7.64 16.9 8.45 12.13 6.1 11.45 4.8 12 4.56 12.1 5.63 13.3 6.96 10.55 5.74 6.8 3.42 7.3 3.27 Tenebrionoidea 29.5 4 18.7 4.3 17 3.45 14.6 2 14.2 3.5 13 2.65 13.05 2.4 14.3 1.7 10.5 2 11.32 2.7 11.1 2.5 8.7 1.75 9.73 2.6 7.85 1 9.45 1.6 8.23 1.53 6.5 1.3 6.65 1.75 6.95 1.15 7.6 1.35 8.85 1.62

335

WL/BL,% ML/WL,% 250 69 80.6 95.7 93.1 105.4 101.2 114.6 147 106.4 104.1 126.3 142.4 158.3 144.5 119.3 139

42 40.1 34.3 46.2 35.6 47.6 50 50.3 41.9 38 46.5 52.3 54.4 50.3 44.8

92.2 98.4 91.9 85.9 83.5 90.3 93.2 102 84 94.3 92.5 79 97.3 78.5 94.5 91.4 72.2 78.2 83.7 91.6 110.6

13.6 23 20.3 13.6 24.6 20.4 18.3 12 19 23.9 22.5 20.1 26.7 12.7 16.9 18.6 20 26.3 16.1 17.8 18.3

336

EVOLUTION OF THE BEETLE HIND WING, WITH SPECIAL REFERENCE TO FOLDING

Species Pedilus Osphya Diaperis Mycterus Mycetoma Bolitophagus Prostomis Steropes Colydium Elacatis Mycetophagus Pycnomerus Ischalia Monomma Notoxus Salpingus Scraptiidae Gen.sp. Bitoma Anaspis Tetratoma Histanocerus Aderus

BL, mm 8 8 7.5 7 6.1 6.1 6 6 6 5.6 5.4 5 5 5 4 4 4 3.5 3.5 3 2.7 2.5

WL, mm 6.9 7.3 11.1 9 7.15 6.6 4.8 5 5.28 5.3 6.05 3.98 5.8 6.1 5.5 3.85 3.84 3.18 3.88 4.12 3.2 2.69

ML, mm 1.37 1.8 5.65 1.85 2.42 2.205 1.35 1.315 1.5 2 1.83 1.3 1.7 2.25 2.3 1.87 0.83 1.03 0.98 1.62 1.57 1.03

WL/BL,% ML/WL,% 83.8 19.9 91.3 24.7 148 50.9 128.6 20.6 117 33.8 108 34.1 80 28.1 83.3 26.3 87.9 28.4 94.6 37.7 107.7 30.2 79.5 32.7 116 29.3 132.6 31.2 137.5 41.8 96.3 48.4 95.9 21.5 90.7 32.2 110.7 25.2 137.2 39.4 118.5 48.9 107.5 38.1

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