2 Insect Diversit y 1 . Intr oduc t ion I n this chapter, we shall examine the evolutionar y development of the tremendous variet y of insects that we see toda y . From the limited fossil record it would appear that the earliest insects were win g less, th y sanuranlike forms that abounded in the Silurian and Devonian pe - r i o d s. T h ema j or a d vance ma d e b yt h e i r d escen d ants was t h eevo l ut i on o f w i ngs, f ac ili tat i ng di spersa l an d ,t h ere f ore, co l on i zat i on o f new h a bi tats. Dur i ng t h e Car b on if erous an d Per- m i an per i o d st h ere was a mass i ve a d apt i ve ra di at i on o f w i n g e df orms, an di t was at t hi st i me t hat most of the modern orders had their be g innin g s. Althou g h members of man y of thes e orders retained a life histor y similar to that of their win g less ancestors, in which the chan g e f rom j uven il etoa d u l t f orm was gra d ua l (t h e h em i meta b o l ous or exopterygote or d ers), i n ot h er or d ers a lif e hi story evo l ve di nw hi c h t h e j uven il ean d a d u l tp h ases are separate db y a pupa l sta g e(t h e h o l ometa b o l ous or en d opter yg ote or d ers). T h e g reat a d vanta g eo fh av i n g a pupal sta g e (althou g h this is neither its ori g inal nor its onl y si g nificance) is that the j uvenile and adult sta g es can become ver y different from each other in their habits, thereb y avoidin g compet i t i on f or t h e same resources. T h eevo l ut i on o f w i ngs an dd eve l opment o f a pupa l stage h ave h a d suc h a pro f oun d e ff ect on t h e success o fi nsects t h at t h ey w ill b e di scusse d as separate top i cs i n some d eta il b e l ow . 2. Pr i m i t i ve W i ngless Insect s The earliest win g less insects to appear in the fossil record are Microcor y phia (Archeognatha) (bristletails) from the Lower Devonian of Quebec (Labandeir a et al. , 1988) an d M iddl eDevon i an o f New Yor k (S h ea r et a l. , 1984). T h ese, toget h er w i t hf oss il Monura (F i gure 2.1A) an d Zygentoma (s il ver fi s h )(F i gure 2.1B) f rom t h e Upper Car b on if erous an d Permian periods, constitute a few remnants of an ori g inall y extensive apter yg ote fauna that existed in the Silurian and Devonian periods. Primitive features of the microcor y phians include the monocondylous mandibles which exhibit segmental sutures, fully segmented ( i .e., l eg lik e) max ill ary pa l ps w i t h two term i na l c l aws, a di st i nct r i ng lik esu b coxa l segment on t h e meso- an d metat h orax ( i na ll rema i n i ng Insecta t hi s b ecomes fl attene d an df orms part of the pleural wall), undivided cercal bases, and an ovipositor that has no g onan g ulum. 2 5 26 CHAPTER 2 m s- a r- t h e 7 – o r.] The earl y bristletails, like their modern relatives, perhaps fed on al g ae, lichens, and debris . The y escaped from predators b y runnin g and j umpin g , the latter achieved b y abrupt flexin g o f the abdomen . M onura are un i que among Insecta i nt h at t h ey reta i n cerca ll egs (Ku k a l ov´a-Pec k , 1 98 5 ). Other primitive features of this group are the segmented head, fully segmente d m ax ill ar y an dl a bi a l pa l ps, l ac k o f diff erent i at i on o f t h et h orac i cse g ments, se g mente d abdominal le g lets, the lon g caudal filament, and the coatin g of sensor y bristles over the bod y ( Kukalov´a-Peck, 1991). Features the y share with the Z yg entoma and Pter yg ota are dicond y- l ous man dibl es, we ll -sc l erot i ze d t h orac i cp l eura, an d t h e gonangu l um, l ea di ng Ku k a l ov´a- P ec k (1987) to suggest t h at t h e Monura are t h es i ster group o f t h e Zygentoma + P terygota . Carpenter (1992), h owever, i nc l u d e d t h e Monura as a su b or d er o f t h eM i crocor y p hi a. S h ea r and Kukalov´a-Peck (1990) su gg ested, on the basis of their morpholo gy , that monurans probabl y lived in swamps, climbin g on emer g ent ve g etation, and feedin g on soft mat- ter. Escape f rom pre d ators may h ave occurre d ,as i nt h eM i crocoryp hi a, b y runn i ng an d j ump i ng . In contrast to t h e i r rap idl y runn i ng, mo d ern re l at i ves, t h e ear l ys il ver fi s h , f or examp l e , the 6 -cm-lon g. Ramsdele p idion schuster i ( Fi g ure 2.1B), with their weak le g s, probabl y av oided predators b yg enerall y remainin g concealed. When exposed, however, the numer - o us long bristles that covered the abdominal leglets, cerci, and median filament may hav e prov id e d a hi g hl y sens i t i ve, ear l y warn i ng system. O f part i cu l ar i nterest i nany di scuss i on of apterygote re l at i ons hi ps i st h e extant s il ver fi s h Tric h o l epi d ion g ertsc hi ,di scovere di n California in 19 6 1. The species is sufficientl y different from other recent Z yg entoma that i t is placed in a separate famil y Lepidotrichidae, to which some Oli g ocene fossils als o belon g . Indeed, Tricholepidion p ossesses a number of features common to both Microco - ryphia and Monura (see Chapter 5 , Section 6), leading Sharov (1966) to suggest that the f amily to which it belongs is closer than any other to the thysanuranlike ancestor of the f f P ter yg ota . 27 IN S E C TDI V ER S IT Y 3 . Evolution of Win g ed Insects 3.1. Ori g in and Evolution of Win g s T h eor i g i no fi nsect w i ngs h as b een one o f t h e most d e b ate d su bj ects i n entomo l ogy f or c l ose to two centur i es, an d even to d ay t h e quest i on rema i ns f ar f rom b e i ng answere d . Most authors a g ree, in view of the basic similarit y of structure of the win g s of insects, both fossil and extant, that win g s are of monoph y letic ori g in; that is, win g s arose in a sin g le g roup o f ancestral apterygotes. Where disagreement occurs is with respect to (1) whether the win g precursors (pro-w i ngs) were f use d to t h e b o d y or were art i cu l ate d ; (2) t h e pos i t i on(s) o n th e b o d yatw hi c h pro-w i ngs d eve l ope d (an d ,re l ate d to t hi s, h ow many pa i rs o f pro-w i ng s ori g inall y existed); (3) the ori g inal functions of pro-win g s; (4) the selection pressures that led to the formation of win g s from pro-win g s; and (5) the nature of the ancestral insects; t hat is, were they terrestrial or aquatic, were they larval or adult, and what was their size (Wootton, 1986, 2001; Brodsky, 1994; Kingsolver and Koehl, 1994). At t h e core o f a ll t h eor i es on t h eor i g i no f w i ngs i st h e matter o f w h et h er t h e pro - w in g s initiall y were out g rowths of the bod y wall (i.e., non-articulated structures) or were h in g ed flaps. Althou g h there have been several proposals for win g ori g in based on non- articulated pro-wings (see Kukalov´a-Peck, 1978), undoubtedly the most popular of these is the Paranotal Theory, suggested by Woodward (1876, cited in Hamilton, 1971), and sup- ported by Sharov (19 66 ), Hamilton (1971), Wootton (197 6 ), Rasnitsyn (1981), and others. T he theor y is based on three pieces of evidence: (1) the occurrence of ri g id ter g al out g rowth s (win g pads) on modern larval exopter yg otes (onto g en y recapitulatin g ph y lo g en y ); (2) th e occurrence in fossil insects, both winged (Figure 2.5) and wingless (Figure 2.1B), of large paranota ll o b es w i t h a venat i on s i m il ar to t h at o f mo d ern w i ngs; an d (3) t h e assume dh omo l - ogy o f w i ng pa d san dl atera l a bd om i na l expans i ons, b ot h o f w hi c hh ave r i g id connect i on s w ith the ter g a and, internall y , are in direct communication with the hemol y mph . Essentiall y the theor y states that win g s arose from ri g id, lateral out g rowths (paranota) of the thoracic ter g a that became enlar g ed and, eventuall y , articulated with the thorax. I t p resumes t h at, w h ereas t h ree p a i rs o fp aranota ll o b es were id ea lf or att i tu di na l contro l (se e b e l ow), on l ytwopa i rs o ffl app i ng w i ngs were necessary to prov id e a mec h an i ca ll ye ffi c i en t s y stem f or fligh t. (In d ee d ,as i nsects h ave e vo l ve d t h ere h as b een a tren d towar d t h ere d uct i o n of the number of functional win g s to one pair [see Chapter 3, Section 4.3.2]). This free d t he prothorax for other functions such as protection of the membranous neck and servin g as a b ase f or attac h ment o f t h e musc l es t h at contro lh ea d mo v ement. Var i ous suggest i ons h ave b een ma d e to account f or d eve l opment o f t h e paranota. For example, Alexander and Brown (19 6 3) proposed that the lobes functioned ori g inall y as or g ans of epi g amic displa y or as covers for pheromone-producin gg lands. Whalle y (1979 ) and Dou g las (1981) su gg ested a role in thermore g ulation for the paranota, an idea that h as received support from the experiments of Kingsolver and Koehl (1985) using models . M ost aut h ors, h owever, h ave tra di t i ona ll y b e li eve d t h at t h e paranota arose to protect t h e i n- sect, espec i a ll y, per h aps, i ts l egsorsp i rac l es. En l argement an d art i cu l at i on o f t h e paranota l lobes were associated with movement of the insect throu g h the air. Packard (1898, cited i n Wi gg lesworth, 1973) su gg ested that win g s arose in surface-dwellin g , j umpin g insects and served as gliding planes that would increase the length of the jump. However, the almost sync h ronous evo l ut i on o fi nsect w i ngs an d ta ll p l ants supports t h e id ea t h at w i ngs evo l ve d in insects living on plant foliage. Wigglesworth (19 6 3a,b) proposed that wings arose in small aerial insects where li g ht cuticular expansions would facilitate takeoff and dispersal. 28 CHAPTER 2 The appearance later of muscles for movin g these structures would help the insect to lan d the ri g ht wa y up. Hinton (19 6 3a), on the other hand, ar g ued that the y evolved in somewha t l ar g er insects and the ori g inal function of the paranota was to provide attitudinal control i n f a lli ng i nsects. T h ere i sano b v i ous se l ect i ve a d vantage f or i nsects t h at can l an d “on t h e i r f eet,” over t h ose t h at cannot, i nt h e escape f rom pre d ators. As t h e paranota i ncrease di n s i ze, t h e y wou ld b ecome secon d ar ily i mportant i n ena bli n g t h e i nsect to glid e f or a g reater distance. Flower’s (19 6 4) theoretical stud y examined the h y potheses of both Wi gg leswort h and Hinton. Flower’s calculations showed that small pro j ections (rudimentar y paranotal l o b es) wou ld h avenos i gn ifi cant a d vantage f or very sma ll i nsects i n terms o f aer i a ldi s- persa l . However, suc h structures wou ld con f er great a d vantages i n att i tu di na l contro l an d , l ater, g lid e per f ormance f or i nsects 1–2 cm i n l engt h .F l ower’s proposa l s h ave b een ex- amined experimentall y throu g h the use of models (Kin g solver and Koehl, 1985; Wootto n and Ellin g ton, 1991; Ellin g ton, 1991; Hasenfuss, 2002). These studies have served to em - phasize the importance of the ancestral insect’s body size, as well as confirming that even q u i te sma ll pro j ect i ons cou ld contr ib ute to sta bili ty (a poss ibl ero l e f or appen d ages suc h as antennae, l egs, an d cerc i s h ou ld not b e i gnore d , h owever). Anot h er cons id erat i on i st he i nsect’s speed on landin g (and whether the insect mi g ht be dama g ed). Ellin g ton’s (1991 ) anal y sis su gg ested that the win g lets mi g ht have been important in reducin g this termina l v elocity, and there would be strong selection pressure to increase their size as a means o f f urt h er re d uc i ng l an di ng spee d. In t h e Paranota l T h eory a cr i t i ca l step i nt h e trans i t i on f rom g lidi ng to fl app i ng fli g ht w ould be the development of a hin g e so that the win g lets became articulated with the bod y. Most supporters would su gg est that this would occur simpl y to improve the insect’s control o f attitude or landin g speed, thou g h various non-aerod y namic functions ma y also have been i mprove d t h roug h t h e d eve l opment o f art i cu l ate d w i ng l ets. For examp l e, K i ngso l ver an d K oehl (198 5 ) noted the potential for more efficient thermoregulation that would arise fro m h av i n g mova bl ew i n gl ets. Ot h er aut h ors h ave su gg este d t h at t h e hi n g eevo l ve di n i t i a lly in o rder that the pro j ections could be folded alon g the side of the bod y , thereb y enablin g the i nsect to crawl into narrow spaces and thus avoid capture. Onl y later would the movement s b ecome su ffi c i ent l y strong as to ma k et h e i nsect more or l ess i n d epen d ent o f a i r current s f or i ts di str ib ut i on. In t hi s h ypot h es i st h e ear li est fl y i ng i nsects wou ld rest w i t h t h e i rw i ng s sprea d at r i g h t ang l es to t h e b o d y, as d omo d ern d ragon fli es an d may fli es. T h e fi na l ma j or step in win g evolution was the development of win g foldin g , that is, the abilit y to draw the win g s when at rest over the back. This abilit y would be stron g l y selected for, as it w ould confer considerable advantage on insects that possessed it, enabling them to hide i n ve getat i on, i n crev i ces, un d er stones, etc., t h ere b y avo idi ng pre d ators an dd es i ccat i on. An i mp li c i t part o f t h e Paranota l T h eory i st h at t hi sa bili ty evo l ve di nt h ea d u l t stage. It was Oken (1811, cited in Wi gg lesworth, 1973) who made the first su gg estion that w in g s evolved from an alread y articulated structure, namel yg ills. Woodworth (1906, cite d i n Wigglesworth, 1973), having noted that gills are soft, flexible structures perhaps not e as il y converte d ( i nanevo l ut i onary sense) i nto r i g id w i ngs, mo difi e d t h eG ill T h eory by suggest i ng t h at w i ngs were more lik e l y f orme df rom accessory g ill structures, t h emova ble gill p l ates w hi c h protect t h e gill san d cause water to c i rcu l ate aroun d t h em. T h e gill p l ates, b y their ver y functions, would alread y possess the necessar y ri g idit y and stren g th. Thi s proposal receives support from embr y olo gy , which has shown abdominal se g mental g ills of l arva l Ep h emeroptera to b e h omo l ogous w i t hl egs, not w i ngs. W i gg l eswort h (1973 , 1 97 6 ) resurrected, and attempted to extend, the Gill Theory by proposing that in terrestrial apter yg otes t h e h omo l o g ues o f t h e gill p l ates are t h e coxa l st yli ,an di twas f rom t h et h orac ic 29 IN S E C TDI V ER S IT Y coxal st y li that win g s evolved. Kukalov´a-Peck (1978) stated that the homolo gy of the win gs and st y li as proposed b y Wi gg lesworth was not acceptable and pointed out that win gs are alwa y s located above the thoracic spiracles, whereas le g s alwa y s articulate with the th orax b e l ow t h esp i rac l es. In support o f W i gg l eswort h ’s proposa l , i ts h ou ld b e note d t h at pr i m i t i ve l yw i ngs are move db y musc l es attac h e d to t h e coxae (see C h apter 14, Sect i o n 3.3.3) an d are trac h eate dbyb ranc h es o f t h e l e g trac h eae . G raduall y , the “articulated pro-win g s” proposal has g ained support, drawin g on ev - idence from paleontolo gy , developmental biolo gy , neurobiolo gy , g enetics, comparativ e anatomy, an d transp l ant exper i ments. Among i ts l ea di ng proponents i sKu k a l ov´a-Pec k (1978, 1983, 1987) w h o not on l y presente d a strong case f oraw i ng or i g i n f rom art i cu l ate d pro-w i ngs, b ut s i mu l taneous l y cast ma j or d ou b tont h e paranota l t h eory an d t h eev id ence f o r it. She ar g ued that the fossil record supports none of this evidence. Rather, it indicates j ust t he opposite sequence of events, namel y , that the primitive arran g ement was one of freel y movable pro-wings on all thoracic and abdominal segments of juvenile insects, and it wa s f rom t hi s arrangement t h at t h e fi xe d w i ng-pa d con di t i on o f mo d ern j uven il e exopterygotes ev ol ve d . Accor di ng to Ku k a l ov´a-Pec k , numerous f oss ili ze dj uven il e i nsects h ave b een f oun d w ith articulated thoracic pro-win g s. However, with few exceptions even in the earliest fossi l insects, both j uvenile and adult, the abdominal pro-win g s are alread y fused with the ter ga and frequently reduced in size. Some juvenile Protorthoptera with articulated abdomina l pro-w i ngs h ave b een d escr ib e d ,an di n extant Ep h emeroptera t h ea bd om i na l pro-w i ngs are reta i ne d as mova bl eg ill p l ates . I n proposin g her ideas for the ori g in and evolution of win g s, Kukalov´a-Peck emphasized t hat these events probabl y occurred in “semiaquatic” insects livin g in swamp y areas and feedin g on primitive terrestrial plants, al g ae, rottin g ve g etation, or, in some instances, othe r sma ll an i ma l s. It was i n suc hi nsects t h at pro-w i ngs d eve l ope d .T h e pro-w i ngs d eve l ope d on a ll t h orac i can d a bd om i na l segments (spec ifi ca ll y f rom t h eep i coxa l ex i te at t h e b ase o f eac h l e g ), were present i na ll i nstars, an d at t h e outset were hi n g e d to t h ep l eura (not t h e ter g a) . W ith regard to the selection pressures that led to the origin of pro-wings, Kukalov´ WW a-Peck ´ u sed ideas expressed b y earlier authors. She su gg ested that pro-win g sma y have functioned i n i t i a ll yassp i racu l ar fl aps to prevent entry o f water i nto t h e trac h ea l system w h en t h e i nsect s b ecame su b merge d or to prevent l oss o f water v i at h e trac h ea l system as t h e i nsects c li m b e d vegetat i on i n searc h o ff oo d .A l ternat i ve l y, t h ey may h ave b een p l ates t h at protecte d t h e g ills and/or created respirator y currents over them, or tactile or g ans comparable to (but no t h omolo g ous with) the coxal st y li of th y sanurans. Initiall y , the pro-win g s were saclike an d internally confluent with the hemocoel. Improved mechanical strength and efficiency would b ega i ne d , h owever, b y fl atten i ng an db y restr i ct i ng h emo l ymp hfl ow to spec ifi cc h anne ls (ve i n f ormat i on). Ku k a l ov´a-Pec k specu l ate d t h at eventua ll yt h e pro-w i ngs o f t h et h ora x and abdomen became structurall y and functionall y distinct, with the former g rowin g lar ge enou g h to assist in forward motion, probabl y in water. This new function of underwater rowing would create selection pressure leading to increased size and strength of pro-wings, i mprove d muscu l ar coor di nat i on, an db etter art i cu l at i on o f t h e pro-w i ngs, ma ki ng rotat i on poss ibl e. T h ese i mprovements wou ld a l so i mprove att i tu di na l contro l ,g lidi ng a bili ty, an d th ere f ore surv i va l an ddi spersa lf or t h e i nsects if t h e yj umpe d or f e ll o ff ve g etat i on w h en on land. The final phase would be the development of pro-win g s of sufficient size and mobilit y t hat fli g ht became possible. Ama j or diffi cu l ty i nt h et h eory t h at w i ngs arose f rom art i cu l ate d pro-w i ngs i n aquat i c or amp hibi ous ancestors i stoexp l a i n sat i s f actor il yt h e nature o f t h e i nterme di ate stages. Th at i s, h ow cou ld fli ers evo l ve f rom sw i mmers? Mar d en an d Kramer ( 1994 ) ma d et h e 30 CHAPTER 2 f ascinatin g su gg estion that surface skimmin g , as seen in some livin g stoneflies (Plecoptera) and the subadult sta g e of some ma y flies (Ephemeroptera), ma y represent this intermediat e phase. Essentiall y , surface skimmin g is runnin g on the water surface, usin g the weak flappin g m ovements o f t h ew i ngs to generate propu l s i on. Because t h e water supports t h ewe i g h to f t h e i nsect’s b o d y, t h e muscu l ar d eman d so f s ki mm i ng are f ar l ess t h an t h ose requ i re din a f u lly a i r b orne i nsect. T h us, stone fli es w i t h qu i te sma ll w i n g san d wea k fligh t musc l e s c an surface skim . Thomas et al. (2000) combined a molecular ph y lo g enetic anal y sis of th e P lecoptera with an examination of locomotor behavior and win g structure in representatives of f am ili es across t h eor d er. T h e i r stu d ys h owe d t h at sur f ace s ki mm i ng, a l ong w i t h wea k fli g h t, i s a reta i ne d ancestra l tra i t i n stone fli es, support i ng t h e h ypot h es i st h at t h e fi rs t wi nge di nsects were sur f ace s ki mmers. Mar d en an d T h omas (2003) h ave prov id e df urt h er support for Kukalov´a-Peck’s proposals b y stud y in g the Chilean stonefl y Diam p hi p no p sis s amali. The weakl y fl y in g adults o f D. samali use their forewin g s as oars to row across th e w ater surface. Further, they retain abdominal gills. The larval stage is amphibious, living b y d ay i n f ast-mov i ng streams, b ut f orag i ng at t h e water’s e d ge b yn i g h t. T h us, D. s ama l i m ay represent a very ear l y stage on t h e roa d to true fli g h t: an amp hibi ous lif esty l e, t he c o-occurrence of win g s and g ills, and the abilit y to row on the water surface. In addition to her views on win g ori g in, Kukalov´a-Peck has also speculated on th e ev olution of fused wing pads in juveniles and wing folding. Noting that the earliest flying i nsects h a d w i ngs t h at stuc k out at r i g h t ang l es to t h e b o d y, Ku k a l ov´a-Pec k po i nte d out t h at , as t h ey d eve l ope d ( i n an ontogenet i c sense), t h e i nsects wou ld b esu bj ecte d to two se l ect i o n pressures. One, exerted in the adult sta g e, would be toward improvement of fl y in g abilit y ; the o ther, which acted on j uvenile instars, would promote chan g es that enabled them to escape o r hide more easil y under ve g etation, etc. In other words, it would lead to a streamlinin g of b o d ys h ape i n j uven il es. In most Pa l eoptera stream li n i ng was ac hi eve d t h roug h t h e ev o l ut i on o f w i ngs t h at i n ear l y i nstars were curve d so t h at t h et i ps were di recte db ac k war d . A t eac h mo l t, t h e curvature o f t h ew i n g s b ecame l ess unt il t h e “stra igh t-out” pos i t i on o f the full y developed win g s was achieved. Two other g roups of paleopteran insects became m ore streamlined as j uveniles throu g h the evolution of a win g -foldin g mechanism, a feature t h at was a l so a d vantageous to, an d was t h ere f ore reta i ne di n, t h ea d u l t stage. T h e fi rst o f t h ese groups, t h e f oss il or d er D i ap h anoptero d ea, rema i ne d pr i m i t i ve i not h er respects an dis i ncluded therefore in the infraclass Paleoptera (Table 2.1 and Figure 2. 6 ). The second group , w hose win g -foldin g mechanism was different from that of Diaphanopterodea, containe d the ancestors of the Neoptera. The g reatest selection pressure would be exerted on the older juvenile instars, which could neither fly nor hide easily. In Kukalov´a-Peck’s scheme, the old er j uven il e i nstars were eventua ll y rep l ace db yas i ng l e metamorp hi c i nstar i nw hi c h t h e i ncreas i ng c h ange o ff orm b etween j uven il ean d a d u l t cou ld b e accomp li s h e d .To f urt h er aid streamlinin g and, in the final j uvenile instar, to protect the increasin g l y more delicat e w in g s developin g within, the win g sof j uveniles became firml y fused with the ter g aan d m ore sclerotized, that is, wing pads. This state is comparable to that in modern exopterygote (h em i meta b o l ous) i nsects. Furt h er re d uct i on o f a d u l t structures to t h epo i nt at w hi c h t h e y e x i st unt il metamorp h os i sasun diff erent i ate d em b ryon i ct i ssues ( i mag i na ldi scs) b eneat h t h e j uven il e i nte g ument l e d to t h een d opter yg ote ( h o l ometa b o l ous) con di t i on, t h at i s, t h e ev olution of the pupal sta g e (Section 3.3). R e g ardless of their ori g in, the win g s of the earliest fl y in g insects were presumabl y w e ll -sc l erot i ze d , h eavy structures w i t h numerous ill - d e fi ne d ve i ns. S li g h t traces o ffl ut i n g ( t h e f ormat i on o f a l ternat i ng concave an d convex l ong i tu di na l ve i ns f or a dd e d strengt h ) m a yh ave b een apparent (Ham il ton, 1971). T h ew i n g s (an d fligh te ffi c i enc y ) were i mprove d 31 IN S E C TDI V ER S IT Y T ABLE 2 . 1 . The Major Groups of Pterygota D ivisions within Neopter a I nfraclass O rder s Mart y nov’s scheme Hamilton’s scheme Paleodictyoptera a Megasecopter a a D i a ph ano p tero d ea a P aleo p tera ⎧ ⎪ ⎧ ⎧ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎨ ⎪ ⎪ ⎪ ⎨ ⎨ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎩ ⎪ ⎪ P e rm ot h e mi st i da a Pr otodo n ata a Od onata ( d ra g on fli es, d amse lfli es) Ep h emeroptera (ma yfli es ) Protort h optera a D i ct y optera (coc k roac h es, mant id s ) Iso p tera (termites) O rthoptera (grasshoppers, locusts, crickets ) M i omopter a a P li coneo p teraProte ly troptera a ⎫ ⎪ ⎫⎫ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎬ ⎪⎪ ⎪ ⎬ ⎬ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎭ ⎪ ⎪ Dermaptera (earwigs ) G ry ll o bl atto d ea (gry ll o bl att id s) ⎫ ⎪ ⎫ ⎫ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎬ ⎪ ⎪ ⎪ ⎬ ⎬ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎭ ⎪ ⎪ P o l yneoptera Manto p hasmatodea Phasmida (stick and leaf insects) Em bi optera (we b sp i nners ) Para p leco p tera a C aloneurode a a Protoper l ar i a a P l eco p tera (stone fli es) Z ora p tera (zora p terans) N eoptera ⎧ ⎪ ⎧⎧ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎨ ⎪⎪ ⎪ ⎨⎨ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎩ ⎪ ⎪ G lossel y trode a a Psoco p tera ( b oo kli ce ) Phthiraptera (biting and sucking lice) ⎫ ⎪ ⎫⎫ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎬ ⎪ ⎪ ⎪ ⎬⎬ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎭ ⎪ ⎪ P araneo p tera Hemiptera (bugs ) T hy sanoptera (t h r i ps ) Megaloptera (dobsonflies, aIderflies ) ⎫ ⎪ ⎫⎫ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎬ ⎪⎪ ⎪ ⎬⎬ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎭ ⎪ ⎪ P l anoneoptera Ra phidi o p tera (sna k e fli es ) Neuroptera (lacewin g s, mantispids) ⎫ ⎪ ⎫⎫ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎬ ⎪ ⎪ ⎪ ⎬⎬ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪ ⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎪ ⎪⎪ ⎭ ⎪ ⎪ Mecoptera (scorp i on fli es) Le pid o p tera ( b utter fli es, mot h s) Tricho p tera (caddis flies ) O ligoneoptera Diptera (true flies ) Si p h onaptera ( fl eas) H y menoptera ( b ees, wasps, ants, i chneumons ) Coleoptera (beetles ) S treps i ptera (sty l opo id s) a Entirel y fossil orders . b y a reduction in sclerotization, as seen in Paleoptera. Onl y the articulatin g sclerites at the base of the wing and the integument adjacent to the tracheae remained sclerotized, the latter g i v i ng r i se to t h eve i ns. F l ut i ng was accentuate di nt h ePa l eoptera, an d t h e di sta l area o f t h e w in g was additionall y stren g thened b y the formation of non-tracheated intercalar y veins and numerous crossveins (Hamilton, 1971, 1972). 32 CHAPTER 2 F I GU RE 2.2 . A proposed g round plan of win g articulation and win g venation. Abbreviations: A, anterior; A n, anal; C, costa; Cu, cubitus; J, jugal; M, media; P, posterior; PC, precosta; R, radius; Sc, subcosta. [After J . Ku k a l ov´a-Pec k , 1983, Or igi no f t h e i nsect w i n g an d w i n g art i cu l at i on f rom t h e art h ropo d an l e g, C an. J. Zoo l. 61 : 1618–1669. B y permission of the National Research Council of Canada and the author. ] K u k a l ov´a-Pec k (1983) ar g ue d t h at t h e g roun d p l an o f w i n g art i cu l at i on i nc l u d e d e igh t rows of four articulatin g sclerites (Fi g ure 2.2). These sclerites were derived, in her view, f rom the epicoxa of the primitive le g and, as a result, were moved b y ancestral le g muscles . O riginating on the outer edge of each row was a wing vein. This articular arrangement, seen o n l y i nD i ap h anoptero d ea, a ll owe d t h esc l er i tes to b e crow d e d an d s l ante db y contract i on o f t h ese musc l es, so t h atapr i m i t i ve f orm o f w i ng f o ldi ng cou ld occur. In a ll ot h er Pa l eoptera, f ossil and extant, fusion of sclerites occurred to form axillar y plates that, in turn, became united with some veins. Thou g h the details of this process varied amon g the paleopteran groups, the end result was that, while it undoubtedly strengthened the wing attachment, i t prevente d w i ng f o ldi ng. Essent i a ll y, i nmo d ern Pa l eoptera t h e b ase o f eac h w i ng art i cu l ate s at t h ree po i nts w i t h t h e tergum, t h et h ree ax ill ary sc l er i tes runn i ng i n a stra i g h t li ne a l on g the bod y . In the evolution of Neoptera the axillar y sclerites altered their ali g nment so that e ach win g articulated with the ter g um at onl y two points. This alteration of ali g nment made w ing folding possible . A secon di mportant consequence o f t h ea l tere d art i cu l at i on o f t h ew i ng was a f urt h e r i mprovement i n fli g h te ffi c i ency. In Ep h emeroptera an d , presuma bl y, most or a ll f oss il P aleoptera the win g beat is essentiall y a simple up-and-down motion; in Neoptera eac h w in g twists as it flaps and its tip traces a fi g ure-ei g ht path. In other words, the win g “rows ” throu g h the air, pushin g a g ainst the air with its undersurface durin g the downstroke y e t c utt i ng t h roug h t h ea i rw i t hi ts l ea di ng e d ge on t h e upstro k e. To carry out t hi srow i n g m ot i on e ff ect i ve l y necess i tate d t h e l oss o f most o f t h ew i ng fl ut i ng. On l yt h e costa l are a ( F ig ure 3.27) nee d sto b er igid as t hi s l ea d st h ew i n gi n i ts stro k e, an dfl ut i n gi s reta i ne d here ( Hamilton, 1971 ). Another evolutionar y trend, a g ain leadin g to improved fli g ht, was a reduction in win g w e i g h t, perm i tt i ng b ot h eas i er w i ng tw i st i ng an d an i ncrease d rate o f w i ng b eat i ng (see a l s o C h apter 14, Sect i on 3.3.4). Concom i tant w i t h t hi sre d uct i on i nwe i g h t was a f us i on or l oss of some ma j or ve i ns an d t h e l oss o f crossve i ns. T h e extent an d nature o ff us i on or l oss o f v eins followed certain patterns that, to g ether with other structural features, for example, 33 IN S E C TDI V ER S IT Y lines of flexion and lines of foldin g , are potentiall y important characters on which conclu- sions about the evolutionar y relationships of neopteran insects can be based. Unfortunatel y , complicatin g this important tool has been a tendenc y for authors to use different terminolo- g i es w h en d escr ibi ng t h eve i ns an d w i ng areas o f diff erent groups o fi nsects, an aspect t h at i s d ea l tw i t h more f u ll y i nC h apter 3 (Sect i on 4.3.2) . 3.2. Phylo g enetic Relationships of the Ptery g ota There are some 2 5 –30 orders of living pterygote insects and about 10 containing only f oss il f orms, t h e num b er vary i ng accor di ng to t h e aut h or i ty consu l te d .C l ar ifi cat i on o f t he relationships of these g roups ma y utilize fossil evidence, comparisons of extant forms, or a combination of both. Increasin g l y , morpholo g ical data and molecular information are bein g combined in massive cladistical anal y ses in an effort to resolve some lon g -standin g ar g u- ments. For exam pl e, W h ee l e r et a l. ( 2001) employed 27 5 morphological variables and 18 S and 28S rDNA sequences from more than 120 species of hexapods, plus 6 outgroup repre- sentat i ves, to o b ta i na“ b est- fi t” ana ly s i so f t h ere l at i ons hi ps o f t h e i nsect or d ers. Even so , none of these approaches is entirel y satisfactor y . For example, in extant species secondar y modifications ma y mask the ancestral apomorphic characters. Equall y , molecular studies may g i ve spur i ous resu l ts if t h e samp l es i ze i s too sma ll . Foss il s, on t h eot h er h an d , are re l a- ti ve l y scarce an d o f ten poor l yor i ncomp l ete l y preserve d, * espec i a ll y f rom t h eDevon i an an d L ower Carboniferous periods durin g which a g reat adaptive radiation of insects occurred. By the Permian period, from which man y more fossils are available, almost all of the modern orders had been established. Misidentification of fossils and misinter p retation of structures b y ear l ypa l eonto l og i sts l e d to i ncorrect conc l us i ons a b out t h ep h y l ogeny o f certa i n group s an d t h e d eve l opment o f con f us i ng nomenc l ature. For examp l e , E u g ereo n , aLo w er Perm i a n f oss il w i t h suc ki n g mout h parts, was p l ace di nt h eor d er Proto h em i ptera. It i s now rea li se d t hat this insect is a member of the order Paleodict y optera and is not related to the modern order Hemiptera as was ori g inall y concluded. Likewise the Protoh y menoptera, whose win g venat i on super fi c i a ll y resem bl es t h at o f Hymenoptera, were t h oug h tor i g i na ll yto b e ances - t ra l to t h e Hymenoptera. It i s now apprec i ate d t h at t h ese f oss il s are pa l eopteran i nsects, mos t o f w hi c hb e l on g to t h eor d er Me g asecoptera (Ham il ton, 1972). Carpenter (1992) pu bli s h e d an authoritative account of the fossil Insecta in which he reco g nized nine orders of fossil pter yg otes. With further work, some of these will undoubtedl y require splittin g (i.e., the y are polyphyletic groups), for example, the Protorthoptera [described by Kukalov´ a-Peck and ´ B rauc k mann (1992) as t h e “waste b as k et taxon”!], an d spec i es now c l ass ifi e d i ncertae s e d i s ( o f un k nown a ffi n i ty) w ill b ep l ace di nt h e i r correct taxon (Wootton, 1981). T o aid subsequent discussion of the evolutionar y relationships within the Pter yg ota, t he various orders referred to in the text are listed in Table 2.1 . I t has generally been assumed that the Paleoptera and Neoptera had a common ancestor [in the hypothetical order Protoptera (Sharov, 1966)] in the Middle Devonian, although ther e i sno f oss il recor d o f suc h an ancestor. Remar k a bl y, a recent re-exam i nat i on o f apa i ro f m an dibl es fi rst d escr ib e di n1 9 28 as Rhy nio g nat h a h irsti ,f rom t h e same Lower Devon i a n d e p osits as the collembolan Rhyniella praecursor (Chapter 5, Section 2), su gg ests that w in g ed insects ma y have had a much earlier ori g in than previousl y thou g ht (En g el an d * Many fossil orders were established on the basis of limited fossil evidence (e.g., a single wing). Carpenter (1977) r ecommen d e d t h at at l east t h e f ore an dhi n d w i ngs, h ea d ,an d mout h parts s h ou ld b e k nown b e f ore a spec i men i s ass ig ne d to an or d er. 34 CHAPTER 2 Grimaldi, 2004). The mandibles are not onl y dicond y lic (Chapter 3, Section 3.2.2) but have other features that are characteristic of mandibles of Pter yg ota. In other words, fl y in g i nsects were alread y well established b y the Lower Devonian, some 80 million y ears earlie r t h an prev i ous l y assume d .T hi s conc l us i on agrees w i t h amo l ecu l ar c l oc k stu d y i n di cat i ng t h at i nsects arose i nt h e Ear l yS il ur i an (a b out 430 m illi on years ago), w i t h neopteran f orms present by a b out 390 m illi on y ears a g o (Gaunt an d M il es, 2002). By the Upper Carboniferous period, when conditions became suitable for fossilization , almost a dozen paleopteran and neopteran orders had evolved. Most authors, especiall y pa l eonto l og i sts, cons id er t h ePa l eoptera to b e monop h y l et i can d t h es i ster group to t he Neoptera, an dli st a num b er o f apomorp hi es i n support o f t hi sv i ew (Ku k a l ov´a-Pec k , 1991, 1 998). Furt h er, a recent stu d yo f 18S an d 28S rDNA sequences f rom a l most 30 spec i es o f O donata, Ephemeroptera, and neopterans has provided stron g support for the monoph y l y o f the Paleo p tera (Hovm¨olle r et al. , 2002). However, there are those, notabl y Boudreaux ( 1979), Kristensen (1981, 1989,1995) and Willmann (1998), who, having undertaken cladis - t i c ana l yses o f t h e extant Ep h emeroptera (may fli es) an d O d onata ( d amse lfli es an dd ragon- fli es), b e li eve t h ePa l eoptera to b e parap h y l et i c. In Bou d reaux’s v i ew t h eEp h emeropter a + N eoptera form the sister g roup to the Odonata, while accordin g to Kristensen the best scenario has the Ephemeroptera as the sister g roup of the Odonat a + N eo p tera. Thi s v iew is supported by Wheele r et al. ’s ( 2001) analysis, though these authors examined onl y t h ree spec i es eac h o f O d onata an d Ep h emeroptera. Accor di ng to Ku k a l ov´a-Pec k (1991), wi t hi nt h ePa l eoptera, two ma j or evo l ut i onary li nes appeare d , one l ea di ng to t h epa l eo di cty - o pteroids (Paleodict y optera, Diaphanopterodea, Me g asecoptera, and Permothemistida), th e ot h e r to t h e odo n ato i ds + Ephemeroptera. All paleodict y opteroids (Upper Carboniferous- P ermian) had a h y po g nathous head with piercin g -suckin g mouthparts (Fi g ure 2.3). Adult s an dl arge j uven il es use d t h ese to suc k t h e contents o f cones w hil e younger i nstars pro b - a bl y i ngeste d on l y fl u id s(S h ear an d Ku k a l ov´a-Pec k , 1990). Prot h orac i c extens i ons wer e FIGURE 2.3. P a l eo di ct y optero id s. (A) S teno di ct y a s p. (P a l eo di ct y optera ) ;an d (B) P ermot h em is sp. (Permoth- e mistida). [A, from J. Kukalov´a, 1970, Revisional study of the order Paleodictyoptera in the Upper Carboniferous s h a l es o f Commentr y , France. Part III, Psyc he 77 :1–44. B, f rom A. P. Rasn i ts y nan d D. L. J. Qu i c k e(e d s.), 2 002 , H istory o f Insect s .  c K luwer Academic Publishers, Dordrecht. With kind p ermission of Kluwer Academic P ublishers and the authors. ] [...]... Morphol Embryol 27 :53–60 Wigglesworth, V B., 1963a, Origin of wings in insects, Nature (London) 197:97–98 Wigglesworth, V B., 1963b, Discussion: The origin of flight in insects, Proc R Entomol Soc Lond Ser C 28 :23 – 32 Wigglesworth, V B., 1973, Evolution of insect wings and flight, Nature (London) 24 6: 127 – 129 Wigglesworth, V B., 1976, The evolution of insect flight, Symp R Entomol Soc Lond 7 :25 5 26 9 Willmann,... 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(1977, 19 92) , Boudreaux (1979), Hennig (1981), Kristensen (1981, 1989, 1991, 1995, 1998), Wootton (1981), Kukalov´ -Peck (1985, 1991, 1998), Wheeler et al (20 01), Rasnitsyn and Quicke (20 02) a [geological history and phylogenetic relationships]; Kukalov´ -Peck (1978, 1983, 1987), a ´ Wootton (1986), Ellington (1991), Brodsky (1994), Kingsolver and Koehl (1994), Marden 53 INSECT DIVERSITY 54 CHAPTER 2 and... with the major subgroups forming at a very early date However, opinions differ with respect 41 INSECT DIVERSITY 42 CHAPTER 2 to the constituent sister groups [see Boudreaux (1979), Kristensen (1981, 1989, 1995), Kukalov´ -Peck (1991, 1998), Wheeler et al (20 01), Kukalov´ -Peck and Lawrence (20 04)] a a Currently, the most favored view is that the two primary sister groups are the neuropteroids + Coleoptera... 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D L J Quicke (eds.), 20 02, History of Insects c Kluwer Academic Publishers, Dordrecht.With kind permission of Kluwer Academic Publishers and the authors.] 35 INSECT DIVERSITY 36 CHAPTER 2 Meganeuropsis permiana with a 71-cm wingspan Only recently have protodonate juveniles been discovered (Kukalov´ -Peck, 1991); these had a mask similar to that of odonate a larvae (see Figures 2. 4C and 6.8) Some also . a spec i men i s ass ig ne d to an or d er. 34 CHAPTER 2 Grimaldi, 20 04). The mandibles are not onl y dicond y lic (Chapter 3, Section 3 .2. 2) but have other features that are characteristic of. b y the formation of non-tracheated intercalar y veins and numerous crossveins (Hamilton, 1971, 19 72) . 32 CHAPTER 2 F I GU RE 2. 2 . A proposed g round plan of win g articulation and win g venation anal; C, costa; Cu, cubitus; J, jugal; M, media; P, posterior; PC, precosta; R, radius; Sc, subcosta. [After J . Ku k a l ov´a-Pec k , 1983, Or igi no f t h e i nsect w i n g an d w i n g art i cu l at i on f rom