NO.:{. THE WIN(:-VEN.\'PION Ob' '['HE ( ~ H R Y S O P I D A .

BY It. J . TILT~YARD, M.,4., l i .S~., F.L.S., F. K.S., T J ~ ~ ~ ~ ~ ~ A / L A w ~ ~ ~ ~ FRLLOIV OP TIIR SOCIETY IN Zoo~oc .~ .

I Plates x., x. Ois ('I't.~~rnspa~.enc,y), xi.: i ~ ~ l d cight Text figures.]

Next Lo the ilfyt-mrl~or~tid(c~, whose wring-tenation I have d~; t l t with in No.1 of this series of Studies," the rnost striking arid clorni~rant group of Planipennie is ~uldoubtedly the family Ch I-!/- sopidw. 'L'lie type genus Clri~!/sopcc is represerrted by :I 1st-ge rru~nhel. of speuies throughout till parts of the ~vor.ltl, whicll are known to E11qlis11-s~)cal~irrg r~aturalists as "(Yrl-cc>~i l~scewinga," "Golclerl Eyes," or "Stink-fliesn-the last name or1 accou~lt of tllc a~1)ominable odour which :i ~rurnber of the specics givr out. r l lllese rr~11x1e1.o~~ apecies are a11 very closely relatctl, and are oftell only to be disti~lguishetl by srnall b r ~ t uorrst:tnt dieercnccs itr t l ~ c wing-verration. T~ILIS, 011 the onc hantl, thc gtbrrns G'ht.ysop(6 ha5 all the marks uf I~t~ing a fairly roce~rt, highly specialised, :~~rt l t1ornin;tnt gcnrts (alld llet~cr 011~' in \vhicJr sj)ecialisations ill tlre \\ring-vcnation rniq1:llt ~.easotl;~hiy be lool<etl for); wl.rile, on tlrc other h:tntl, the \cry importance of tlie vt,~r:~tion i t1 the study of tlle genus tlen~:rndh that sli1)shod i~lld l~iipllazard idem of tlic wing-atructurc or~glrt to ceesr, e ~ ~ t l give 1)l:iut. tu syhtetlr brtsetl on sound homologit~h.

r 1 lliosct \vorke~a who 1l;ive I~cetr busy tlrlli~rg tllc. last tell years 01. so, adclirrg 1lrlmc:rous sprcit:.; of Clzry.sopid~r~ to tlrr list, all tippear to l-rave brer~ uoutcnt to t.eg;trtl the. wing-ve,r~atiot~ i l l this family its easy of intelp~-c~txtion alung typical Neuropterous lirres, i .~ . , they rocognised, \vi tlrout ttr~y questioning, a radial sector witlr a number of branches, two series of gradate veins, a straight - - - -- - - - -- - - - - - - - -.

'L'heie Proccethngs, 1915, xl., Part 4, pp.734-752.

222 STUDIES IN AUSTRAI~IAN NEUROPTERA, iii.,

nnhranched media, a forkrd cubitus, arrd two or three short anal veins. Eight throngh the farriily there is so little variation, except iir ~riinor tlrtails, that the Lirnits of these veins, having becw assigircd without :my suflicierlt reason to one species, soon hecarrle applied equally rc~adily to all. From orrc point of view, it inay be argued tlrat it did not matter tlrat tlre detcrminations of the veiration were wrong, since they were all consisfn~tly wroirg, i ~ r ~ d so the nunicrous desci.iptions of new species all conforill to a single plan, and are easy to follow.

Why is it nclcessar.y to disturb them? Tlie answer is a very ol)vious one. I t is not only that f:tlsc hornologies :we not to be tolerated by anyone with the true scientific spirit, but alho that they actually seltloru work well in practice. It is only by pure chance tlrat soulc gerlils of CYhvyso?)idtr has not tinned up which ~vould not have fitted in with the accepted veriational plan, arrd would thus have started a series of evasions and explanations, on whose htxcls confusion might have followcd fast. More than that, again, we can never Ilope to undcr\tand the phylogeny of such a group as the C'hrysopid(~1, unless we really understand its wing-structure, arid its relationship to the gchneral vcrrational plan in the Neuroptera Planipennia.

The lnresent paper was undertaken in the strong belief th;~,t the accepted venations1 scheme for the Crh-ysopidt~ was wrong in certain l~a~ticulars. I was not prepared to adnrit (after my ex- perience in the iYyrti~f?&eonfidcr) that the ineditt, in the forewirrg at any rate,, was an ur~brarlclled vein. I could not find any batisfactory explanation of thc pcrsihtence of the peculiar "divisory veinlet" in the forewing (Text-fig.4, dv), since it i s obviously not in a position of rr~axirnurn effect as a support to any main vein. It seerned to me that this veinlet must be some remnant of the loht lowcr branch of tElc media, arid its absence in the hindwing further strengthened this I~elicf. Finally, I realised that t l ~ c conrrectiorr betweell tl.re vevrakiorial plarrs of t l ~ o Chrysopidm and &och?ysidcrj mas still entirely rnissing, and tlrat we could never hope to oRcr any adequate phylogeny of tho C ~ L I - ~ A ~ I ~ ~ ( I , until this was cleared up. Such beliefs and sus-

picions as thcse deterllri~lctl rrle to undertalie a study of thc pupal wing-trayheation a t the curliest favouwble moment. The chance occurreti during my recent visit to So~itll Queenslantl. ~h?-ysof~id~c~ were cluitc comrrlon, anti i t was easy to obtain, not only larvir* from citrus trees and various conifers, but also eggs ill great abuirdance frorn rllaturc females confined iu pill-boxes. On my ret111-11 to Hyd~ley a t thc cntl of October litst, J l-~rougltt with rrrc. a i~umber of eggs and la~*va,. I also ar~.ai~ged wit11 various correspondents to keep up the supply by post. I n this connectiolr, 1 desire to thank Mibs C. Jensen, of Caboolturc, Queenslanc~, ant1 Mr. I~ulre Gallard, of Epping, near Syrlrley, for maintainirlg a, plentiful supply of larv:~ throughout an extol)-

tionally tlry period of the year, during which the ~carcit~y of aphides made thc rearirrg of those little creatures a ve1.y difficult matter.

Moht of the Aust~,ali;tn spccies of Chrysopidm are riot naulcd. 1 had four species to woi-lr on, three beloi~ging to tlre gerrus Chryso2,n, and orle to ~\'ofhoc.ht.ysa. This last was of largc size, ancl promised fine results. Unfortunately, of all the p u p ob- taincd (mostly f ~ o m Mr. Gallard), nut a single one was suital)l(l for thc work. About hivty ptsr cent. of tl- ern were ichlleumonetl; the re~nainder were far too ad~anced towartls the irnaginal instar to Ije of any v;~luc. Thc next irrost promising was ;I nloderately l a r g ~ species of C'hrysoy~a, not lrnconlrirori both i r r Rrisbanr arid Sydney, ~vhich I slrz~ll desigirate Chrysopcc A, for the putpose5 of tlris 1)aper. T\vo brood5 of this species were rearcd fro111 egg"

laid in Brisbarre. But owir~g to t l ~ c extrelr~e drouglrt, I failed to find errough apliis to kcel) then1 alive, alrd 011ly tllrte pupated &on1 olrt3 of thc'hcl, thr l)hotomicrog~;tph in IPla,tc: xi., fig.3, was obtai~red.

l\n exceedingly hrnall hpecitv,, Clzrysopn H , pupated ill 1lu1nbe1-s. Gut the cocoon\ were :,o \111:~11 (tliameter 1 .L mm.), ant1 the p u p so tlelic.t&e, th;tt only noder rate ~.esultb wtw obtairled with thenr. Tllest* r ~ s ~ ~ l t s Irelpctl r~raterially ill the successful solution of tllct pl.oblc~n in band, but noilc of the l~lrotog~.aplls take~r wcre good erlougl-i to lrublisl~.

224 STUDIES I N AUS'I'RALIAN NEUROPTERA, iii.,

Finally, I had a large supply of larv:~ and pupx of a comrnon species whose larva is found irr all citrus-orchards arou~id Sydney, as well as on roso-bushes. The cocoons were sillaller than T could have wislrcd, arltl the 1)up:e delicate enough to give me much trouble and many failures beforc good could be obtained. Hut T was able to breed a nunlber out, so as to obtain ail imagiilal vcilation sclleme f~.x.nc.fly corresponding with the pupal wiog-tra- chc;~tiori studic:d; thi5 was, indeed, an c.ssential condition for a

successful result. This spccies proved to be one which had pre- viously been deterrnirtcd for me by Mr. Esber~ Pctersen as C. signata Wdlccr. It turnc~l ont, tlierefor~, very fol-tunately, that 1 am aljle, after the uornpe~ative failure of the work done on the unnamed species, to offer n rtsult basctl in almost every detail of completeliess upon tllc vcnation of a single, common, named species.

~Lfethods of Study.

The problem was first attacked dong the exact lines already laid down for the study of the tracheation of the pupal wing in the fMymzrleontidrr. First of all, the exact date of the spinning- np of each larva was recorded, and the cocoons arranged accord- ing to date. Here, a t the very start, an attempt to usc the knowledge p i n e d in the case of the AIFyrn?~lco?~fidce led to disaster. I t will be recalled that the Ant-lion larva does not pupate i ~ t once after spinnirlg its cocoon, but reint~ir~s cluie\cerrt \vithii~ i t for seven or eight days. I therefore kept a nuinher of cocoonb of thc large Nothochrysn for several days, examining them carc- f~ll ly irr a strong light each day. Aft1.1" f o u l or fivc days (by which time the cocoorls n ~ n s t liave I~eerr seven or eight days old, sixrce they had spun up before Mr. G ~ ~ l l i ~ r d 1)osted tllenl to me),

tlie contents began to tlarkcrl ill colour. l'hr lalava I)cir~g couei.ed wit11 a wliitc powdery Ijloo~n, I coiicluded that j~apatior~ 1i:~tl tak(.n place. This was, alas, not tllc cast,; the darkerring was due, rrot to the pupation of the larva, but to the l)upatioi~ of half-a-tlozcn or more iclrneumo~i-grubs withi~l it. Thus se\ era1 valuable days were lost; so that, when at last a cocoon was opened which rcvcaletl a Chrybopid pupa, i t was lriucll too far advanced

towards the imaginal stage to be of any use. In this way the rnost promising cocoons (i.a., the largest) were all wasted.

By this time both Chrysopn, A and Chrysopn, B were spirlning up, so I turned my attention to the larger of the two (A). Here an additional dificulty presented itself in the smallriess and greater delicacy of the cocoon, and the activity of the pupa within it. The cocoon could not be cut open with fine scissors, owing to the fact that the pupa would keep wriggling round so as to face the cut, and thus sooner or bter the delirate wing- cases became damaged, either by pressure or by the lower point of the scissors. I next tried to open a cocoon by ineans of a fine sharp needle, and was delighted to find that this could be done without damaging the wings of the pupa, if certain rules werc adhered to. Firstly, owing to the lnethod of spinning the cocoon, it appeared that the silken envelope does not tear unevenly in all directi:tionb,

a but can be made to split exactly along :triy parallel of latitude (taking the ends of the longest axis as

6 the poles) if the point of the ncedle is exerted in tliat direction. Secondly, if the point selected to

Teut-fig. I . btart on is at about the level of tllc lit1 of tlic cocoon when opcned I!y thc pupa itself naturally, the split conlea ve1.y readily, and tho point of the needle is not liliely to touch the wings of tile wrigglcsome pupa. This position is about the samc :LS that selected wllerl "topping" a boiled egg at breakfast, and is shown in Text-fig. 1.

Having solved the problenl of how to open the cocoon without damaging the pupal wings, the next difficulty Wac to extract th(. pupa, which, t ~ s so011 as the lit1 of the cocoon wab lifted, bec.an,il very active, and kept wriggling round from side to side, 60 a\

:elways to face the point of the needle. 1 fo~md the best plan was to continue the cut until the lid caould be either taken coln-

pletrly off, or turticd over backwards, so as to expose the 1le:td of

the pupa. l f now the pupa, as i t genelaally did, resolutely re- - - - - - -- - - -- - - -- - - --

'"~coo~~ of C'tiry~oprr xiy~tat*. TTTalk., correctly ope~red; ( x (i).

226 STUDIES IN A U S T R A ~ I A N NEUROPTERA, iii.,

fused to'leave thc cocoon, 1 took a ptir of finc forceps, seizcd it cluickly just below tach pl.ojccting eye, and so lifted i t out bodily. This operation nrxy flattell oue or both eyes, but it will rot tlt~magt. the wiilgs.

Pupre of 6"ht*yso2,16 L' wcre extracted from cocoons seven or eight days old. 'l'll(: mi~rgb were pale \vI~itish, and appeared :tt the first gla~rce to hc in elrely wity suited for iny purpose. TSut, under a lens, it ~vits bee11 that the irnaginal wings were, it1 nearly all cases, strongly rucked or crumpled within the wing-slleilth, bo that thc tracheation could not be properly followed out. Henccs the whole of tlris batch of valnablt, larvte and pupre had to hc \:~crificed, in order to tliscover, firstly, how long the larva re- ~rrainrd in the cocoon before pupating, arld secondly, how long it was before mclring of tlle irr~agiilal wing in tho pupd wing-shed1 began to occur. Trr the course of these trials, 1 was forturrate in obtaining a pliotogl-apli of thr hindwing of a pupa of this specieh wllicl~ I doternlined as being nearly three days old ( t h ~ cocoon was over six days old, ant1 the average duration of larval life, bcforc pupatiorr occurrrcl, had been determined as three and a

llalf clays in tho case of this species). I n this photograpll tlle lucking had just I)egurr (Plate xi., fig.3), and this conciition llelpcd to elucidate a knotty qnestio~l of venation, as T have ex- plained below on p.240.

By this time T lract Elopes that 111y difficulties were a t an end, as I rrow lrad left over only material of thc two smallest species, (11~~ysoy~n B and C. siynata. The larvw of Ch~ysopa H fed up a t a great rate, and spun up well ahcat1 of those of C. sigr~atn,

although nlost of the eggs of both species hatelred at about the sarne time. Tlle weather was very l ~ o t and dry, and this rrlity lrave been one cause of their activity. One larva actually spur1 its cocoon on the eighth day after hatching from the cgg, arrd emerged as an irnago six days later! 1 found the cocoons arrd pupie of Chrysopa 13 most tlificult to haudle, since they were so bmall and delicittc. 1-Jowevcl; one was extracted just after the act of puymtion (tlw larval skin baing e\en not fully cast off). This W:L~ killed by being dropped into :L t~ lbe of water, in which

a drop of chloroforn l ~ a d been shalier~ up, and was tl-~rrr placed or1 :L slide on its side, so that its wings could be examined.

A further crop of rlew diflicultieb now arose. 'l'hc lli~l(lwing could not be examined because tlrc forrwing covcl~wl it almoht completely, lying oblicjuely across it; while the forcwjng ill its turn was partly covered by tlre large spiral coil of the irnnlerlaely long arrttmrrt~, wl~icl~ was pressed down flat upor1 it. (sco Text-fig.

3). Moreover, both antenna arld wings were sticky, and coultl not he persuaded to separate, except by in- serting the poiut of a needle between tllenl-- :t pr.oceeding which seenlecl bound to cause sorne dislocation of the delicate tracheal plan. After this separation had heen effected, the long antenna was cut of close to the base, Hw

and removed. The two wings were then ac dissected away with fine scissors, and floated off on to a glass slide. They were then ex- amincd under a low power, wherr it was seen that considerable displacement of the tra- Text-fiy.2."

chcation had taker] place. Enough of the main plan, howevcr, could be matie out to show how rt~markably specittlised it was, and how important it would bt. to obtain an itbsolutely perfect record of it.

By this time 1 was reduced to a single source of s~~pply, viz. Chrysopn suqr~ntn. Fortuntttely rny own Isrvz were supplernentcd by two batcl~es of larvre receivcd frorn Mr. ($allard, so that, in all, I still had some two tloeer~ 1arv;x: svailablt.. Thehc, began to spin up ttbout the ~niddle of November, and had all cornpleted their cocoorrs withirr a frw (lays of one anotller. ,\fter waiti~tg thrce days, 1 opened two cucoo~is, and found that t1lr.y still con- tained larva These cocoons were closed up again, the lids bring held in place by cotton-wool. The following day, one 6f the larvx pupated. This pupa was talcen wherl less than one day -- - - - - - -- - -- - - - - - -

' Pupa of Chrysoprc t\is~~~ata Walk., after extraction fron~ cocoon; ( x I)) . a, antenna: uc, its spiral coil adhering to the forewmg; e, eyc; I l 'tr., fore- w~ng; Htc,, llinclwir~g; i t / , pupal n~andthler.

238 STUDIES IN AUSTRALIAN N ~ J R O P T B R A , iii.,

old, and was treated as explained for the pupa of (JYh~-ysopa H :hove. The dissection wa\ carrird out with the greatest care. U~rt though thercb was scarcely any displacement of tlie trachea- tion, i t was found that a vertain amount of blood-plasma, artd wme fatty tissue, llati fou~rii their way into the [lases of the wings, rendering them too opaque for observation.

I~lirther pupz \vtbrt' now taken, all about one day old, since it ;tppeared that only on the first day or two were the wings frer from rncking within the wing-sheath. The wings wwe carefully disxected 08, but iu 11o case could 1 obtain a satisfactory result. The, wing sheatl~s \vetst, so delicate that thc use of a cover-slip conipletely upset the tracheation; r~lso it seemed quite llopelcss to use the ~ei~bo1.s \vlthout c a ~ ~ s i r ~ g sollie a l te~at io~i ill the positions of the rnairl tracheal sterns.

1 now tried the following plan, which I am glatl to say proved entirely succcssfr~l, :nld enal)letl Ine to obtain the results sho\c 11 ill this l~spcr. Having detc.rmined that the tracheation nrust he stndietl witliout the use of arry dissc~ctiiig methods, 1 took a, pupa of C. s L < ~ L c ~ ( Y i~ l~out orle (lay old, and killed i t in the usual manner. I thcn took two glass slides, and ~rroistened them so as to malie thrrn cling tirrrrly together. Tlre upper slide was selected so ;AS

to I)c as near as possil)l~ of ZL thickness equal to the height of the 1 ~ u p l thorax up to t l ~ c \vir~g-base. Tlris slide way then slippetl back along the lower one, so as to leave 11ear1y irrcl~ of the Iattei. cxposecl. 1 tllcu took hold of the ] ; ) I I ~ E l)y the legs with a t i ~ ~ c forceps, cut olf and ren~ove(I t l ~ e 1.ig1lt wntenila, ant1 carefully separatctl tlle two wirlgs o11 tllc right side, with the poiilt of a,

firlo llecdle. (The m>~rk nladc by t l ~ e needle call be see11 as all ol)licluc tlcl)rc\,siorl ruilning ill horn near the ~niddlc of thc pus- tc\riol I)ortler of the l~intlwilrg ill Plate xi., fig. I ) . The ~ I I ~ A wi~s ~ ~ L C I L pl~('e(l carcf~llly (101vt1, L ~ ~ I . S I I ~ I upwi~lds, 011 t l ~ c f l . c~ portio~r of tilt, lo\+ cr hlirlt., thc right pair of wiilgs I.)eii~g ~;~ls(vl up ho its to lwojcct a t right ang1t.s to t h ~ botly axis, snppol.ted upon thc upljer slltlc. Tlle pnpa a ~ l d its H I I I ~ S w t ~ e kept t l~ t~ro~gl l ly welt with water during this operation. Fillally, tlie body of the pupa W ~ Z S gently pressed ulltil it came to lie close lip to aiid parallel

RY R. J. TILLYARD. 229

with the free edge of tlic upper slide, 80 that thc whole of tl-ic two \vings lay flatly out over this slide (Text-fig.3). No cover- slip was used. (This sanlct operation was aftcrwards prrformed on other pupa>, with thc addition of a cover slip let t l o ~ ~ n gently upon tlie wings; but this was fount1 to citusc disl)lac.ement of some of the trachefe). The wings were tllrri pllotographecl by 111e:~rls cf Reichert's photo-mi(-1.ograp11ic apparatus, :rntl the ~.esults

obtained which are shown in Plate xi., figs.1-2. Inl-

r~rediately afterwards, the cair1el.a- lr~cirla tlrawii~g of tlie tritclieatioi~, shown in Text-fig.5, wi~5 obtainetl from this same pupa. Thus a t last 5uaarrs TV~LS obtained. I may icdll that photographs arid drawings wcxre made from several othcl* 11uprc of C. siqr~atn, and that a11 of thescx agreed practically in (very single tleti~ili with the one figured. Thus the results do not rest upon :t single

Text-fig.3.' observation, but i~r(, baseil up011 i~

considel-ahlc niass of evidence.

Critical St?td?/ of the Ilrir(y- l7~1zafiott oJ' C?~~-yao21a s i q m a f ~ ~ Walki~ .

We cann now pass to tlie study of thc tracheation of thr pupal wing, with ;I view to elucidating the venation of thc irnaginal wing. This latter is shown in Text fig.4 (p.230), with the usually accepted nomenclature of the veins, according to tlie Cornstoclc- Necdham notation. This nomenclature has been eniployed hy Ranks, Petersen, Navhs, and other systematists for the past ten years or more. As far as 1 can gather, nobody has yet doubtccl

* Diagram to show method of studying tlie pupal wings of Ch~ysopa; ( i c 8) : a, coil of left antenna; a', cut end of right anteana; Pw, forewing; Hu,, Ilindwiuy; I;, lo\ver glass slide; P I , pupal mandibles; U, upper i lass slide.

t l n Rome speci~nel~s, t,here may be a s ~ r ~ a l l fork ilt the e l t t r e ~ ~ ~ e t ip of Ks or 8,.

230 STUDIES IN AUSTRALIAN NEUI~OPTERA, iii.,

its general accuracy. Petersen, howevcr, has recerltly stated to mc (in litt.) his conviction that the venation of the Chrysopidre is "the rnost abrlorlnal of all the familiesn-a statement which certainly implies a strong suspicion that this venation is not quite ss ~irnple ;LS the accepted sclleme would make it :tpprer to he.

Tcxt-fig.4.--\\'ings of Ch~ysopa ni!lnatn M1alk.: imago, ( x 9), with the gel~erally accept,ecl ~lotatior~ : ell,, -co ,, the tlrree " cribital cells" of I<ariks; rlc, "divisory veinlet" of Banks; y, inner, ;tncl {I' outer series of grailate veirrs; pt, pterostiglr~a. Other. let,tcrs a s usual in tllc Conistook-Need11:tm notstiort.

The rnost striking feature of tllr Chrysopid wing, if we acccpt the usual r~otatior~ (Text-fig.4) is the fact that it is divided longi- t~~tlinally by a ren~arkably strong, straight, median kcin (M), ter1nin:~ting on the posterior bortkir, l)elo\v thc lcvrl of the ptero- stigma, some dihtance before the apex. In the hi~ltlwing, this vein 1e:xves t l ~ c l.:tdius (Ti ) close to the base, and r1111s i~~~s01uteIy straight tllrolrgh tllc wing. In the forewirlg, how eve^., it sl~ows a slight killk not far from its origin, a t a point wlret-e :LKI obliclue cross-vein clescends to Cu. Tlrc curvc~l portion of the vein M

BY R . J. TILLYARD. 231

bcreabouts is supported underneatlr hy a small vein placed concavely to it, arising from thc cross-vein, and curving up to join the media itself a t or near the foot of the first cross-vein descending froru the radial sector (Rs). This small concave vein has been termed the diuiso9.y v~inIrt (dv) by Banks, : ~ s it is supposed to dividtl the coinplete "third cubital cel17'((a6b3) into two unequal parts. Tllc exact sllape a i d position of this tlivisory veinlet ha-\.e been used by Banks with considerable success in diagnosing the differences bctweev numerous closely elated species. The two undivided cells lying between M and Cu proxiinad to the "kink" arcb tcrinetl by Banks the Jirst and s~cond cubital ce71.9 I-espectively (cu,, c ~ L ~ ) . As it is usaal, ill the Coinstock-Needham terminology, to name the basal spaces after the main veins bounding them abow, and not below, it would have been rnore consistent to have termed these three cells the lLmedian cells," reserving the term "cubital cells" for those in the row below them.

The gradate veins (9, 9') are very constant in position in the Chrysopidce, fornling two series of cross-veins rising, as it were, in a series of steps from the media upwards through the parallel hranches of the radial sector. Often, as in the species urlcler discussion, the inner series of gradate veins (y) is one less in ~lumber than the outer series (y'); sometimes the inner series is much reduced in number.

The form of the pt~rostiyn~a ( p f ) varies greatly in thc different species, and is never of inore than specific value. Tn C. siynnta, there is a distinct greenish pterostigma on both wings. That of the forewing is confined between C and Sc, and supported beneath by six cross-veins between Sc and R. In the hindwing it is denser, and is continued into the space between Sc and R. The cross-veins in this space are, however, present, though not easy to see.

The result of a study of the pupal wing-trachea;tioi~ (Text-fig. 5 ) shows us that the accepted interpretation of the imaginal venation is quite incorrect as regards the media and cubitus of both wings, and 51~0 as regards the origin of the radial sector in

932 STUDIES IN AUSTRALIAN NEUROPTERA, iii.,

the hindwing. 'I'he supposed media and cubitus prove to be two excessively complex veins peculiar to t l ~ e Chrysopidm. The original media and cubitus of this extraordinary wing-venation have become reduced and contorted, so that their courses could not even be guessed a t without reference to the pupal trachea- tion. The two new complex veins do indeed more or less fill

'rext-fig.5.-Tracheation of wings of pupa of C. sigimta Walk. ,( x 54). For lettering, see Explanation of Plate x. (Camera-lucicla drawing from freshly-killed pupa).

the places usually occupied by the media and cubitus in un- specialised Neuropterous wings. Therefore, as i t is quite impos- sible to give to these veins the complex names that would indi- cate their true nature, I propose to name them a t once the pseudo-media and the pseudo-cubitus respectively, in order to facilitate discussion, and to distinguish them clearly from the true media and cubitus. I suggest also the notation M' for the pseudo-media, and Cut for the pseudo-cubitus, as shown in Plate x.

I n order to trace the courses of the true media and cubitus, and to understand how the pseudo-media and pseudo-cubitus have supplanted them in the Chrysopid wing, let us turn now to the study of the pupal tracheation, as shown in Text-fig.5 and

in Plate xi., figs.1-2. As a further aid to this study, I have qiven the correct interpretation of the imaginal wing-venation in Plate x., overlaid in red, on transparent paper, by a diagram- ~ r ~ a t i c representation of the pupal tracheation, to sl~ow the part played by each trachea in the fornatiorl of the veins. We shall divide our study up into three parts, viz., (1) the radial sector and its branches, (2) the true media, and (3) t l ~ e true culr~itus. Having traced these out, we can then visualise the extraordinary structure of the pseudo-media and pseudo-cubitus.

( I ) The R<cdial Sector (Rs) and its Bmnc1~es.-The radial sector (Rs) arises from R, in the forewing, a t a considerable distance from the winglr)ase, a t a point called the rrcdirclforlc ( r f ) . Pupal tracheation and imaginal venation agree on this point. I n the hintlwing, however, the supposed origin of tls in the imaginal venation (the point x) is seen by reference to the pupal trachea- tion to be a false origin, arid really represents the origin of the first cross-vein between R and Rs. The true origin lies much closer to tlre base, a t the point marked which has up till now been taken as the origin of M.

Tn both wings, if we look a t the tracheation, Rs gives off ten poste~~ior I)renchcs. These 1 have named XI, 9, . . . S,, for con- venience of reference (instead of the more cumbrous Es,, Rs,, etc.), Sl being the most distally placed. Turning to the imaginal venation, we see that only six branches of R s are visible, viz., S, to 8,. What has happened to the other four, viz., S, to HI,? The answer is supplied by a glance a t Text-fig.5, followed by a reference to the transparency overlying Plate x. These four branches are, in fact, bent in their middle portior~s so as to r t ~ r ~

longitudinally, and thus give rise to a continuous Banksian Line, homologous with that already shown to exist in a number of Myrmeleontid genera.* For this reason, I propose to call these four brar~ches the four fianhsian sectors, B, to B,. Tllus -- - - - -

'See No.1 of these Studies, in these I'roceerlings, 191.5, pp.734-752, Vol. xl., Part 4. Nar~hs has termed this line in dIy~meleonfad(e the "linea plicata," a singu1:trly inappropriate term, it seems to me, fur a formatloll which, though of composite origin, is in its liighest expresslon an absolutely straiylit lnle wlthont any folding in ~ t s compos~tion.

234 STUDIES IN AUSTI~ALIAN NEUROPTRKA, iii.,

B, = S,, B, = S,, B, = S,, and R, = S,,. I t will he seen a t once that the Ranksian Line formed by the middle longitudinal por- tion of these four sectors is the distal portion of the pseudo media.

The importance of these four Ranksian sectors does not, how- ever, end here. Three of them, viz., B, to B,, after dropping below the level of the pseudo-media, again become bent longi- tudinally to f o ~ m a second IZanksia?~ L i r~e This is clearly seen to be the distal portion of the pseudo-cubitzts.

(2) The true iVedia ( M ) . - In the tracheation, the stem of 35 is distinct from R; in the venation, the two are fused basally for a short distance. The true media then diverges slightly from R, and runs to a point called the median fork ( m f ) , lying imme diately below the radial fork in the hindwing, but a little proximad to i t in the forewing. From here onwards, the course of M in the venation is so disguised that i t is necessary to turn to the tracheation for elucidation. Then we see at once that M has two branches, M, and M,, arising a t mf-a fact which could never have been proved froni the imaginal venation alone. The problem is also complicated by the ~ e r y different behaviour of these two branches in fore and hindwing respectively; so that it will be necessary to trace them out in each wing separately.

Tn the forewing, M, on leaving ntf arches slightly upward, but does not come into contact with Rs, from which i t remains separated by a full cell's width. Tt, then runs longitudinally towards the down-curving portion of B,, and passes close under the sector for a short distance, before i t (M,) turns downwards in a second bend. It then turns to run longitudinally again for a second she$ distance, and again approaches and runs alongside

B, Finally, i t breaks up into two small branches descendir~~ to the wing-border. Thus we see that M, performs the part of another Banksian sector, and helps in turn to form both the pseudo-media and the pseudo-cubitus.

The lower branch, M,, on leaving mJ; runs concavely to M,, and the11 approaches it again, so as to isolate between M, and itself a small oval area, which can be recognised a t once in the imaginal venation as the cell lying just above the "divisory

BY R. J. TILLYARD. 235

veinlet "-the latter, of course, being a portion of M, itself. After running close below M, for a short distance, M, drops down to the level of the pseudo-cubitus, and plays a part, in I~elping to form that vein, exactly similar to tlie part played by

. Finally, i t branches into two, and drops to the wing- border.

I t will be seen that, owing to the fact that MI and M, in the forewing twice recede from and approach towards one another, two curved areas are isolated off between them. I n tlie imaginal venation, owing to the fusion of M, with M, for about half a

cell's-length along the pseudo-media, these two cells are widely separated. The first is tlie sniall cell above the "divisory veinlet " ; the second is the large hexagonal cell lying next distad from the so-called third cubital-cell of Banks (cu, in Text-fig.4). These two cells being enclosed by both branches of the true media, I propose to name the111 the J i r s t and second i~itra-median cells respectively, with the notation zm,, im,, so as to distinguish them clear1 y from the three median cella, m,, m,, and nz,, which are of course the " cubital-cells" of Banks. As regards the term ' L divisory veinlet," this is obviously a most misleading and inaccurate term, since i t is, firstly, not a veinlet a t all, but a portion of the main vein M,, and, secondly, i t does not divide anything, since the true third median cell (LLthird cubital " of Banks) lies entirely outside it. I propose, therefore, to term this srnall portion of M, the median loop, with the notation ml. I t shoultl not be lost sight of, also, that the upper part of the cross-vein from which ml appears to arise is also a portion of AI,, and is thercfore analogous wit11 the upper part of the well-known formation in the Dragonfly wing, called the arculus. I t is not homologous with it, however, since in the Dragonfly wing i t is the main stem of M which drops from R to form the arculus, whereas in the present case i t is M, dropping from M a t mf. The term medi~tu arculus (nza) is suggested as a suitable name for this formation.

I n the hindwing, the behaviour of the true media is different. The main stem M is very short, so that the median fork mf

cnmes directly under the radial forh d; not far from t l ~ c Lase of

236 STUDIES IN AUSTRALIAN NEUROPTEILA, iii.,

the wing. T11us M,, on arching up from mJ; comes a t once close up under Its. There follows an extraordinary sclaptatior~ on the part of this latter trachea and its most proximal branch I + , . ISy means of an upward curving of R s below x, and :L bending of E, convexly to M,, the t r i a ~ ~ g u l a r area between the t h ~ e e trachefe ILs, ??I1, and R, is reduced to a rnininlum. This area is represented in the imaginal venation by the nlinlite triangle f .

Several cox1sequenct.s arise a t once from this, wl~icli can he best noticed by comparing the venation of the hindning with that of thc forewing. Firstly, the portior~ of 13, dercending frorn Rs i~ almost co~r~pletely obliterated. Consequently, thq place of B, ill Ir)oundirig the cell rnark(~d b is take11 by the 01)liquely ascending portion of Rs, wliich rr~eets the c-ross-~ eiri below c As a further consequence of this arrangernrmt, t l ~ e cross-vein from x appears to be the real basal part of Rs, and a appears to be the radial fork. i t is, iricleed, no slur on the intelligence of all those wllo h a t e hitherto worked on this family, that they assumed this to

br so witlrout any doubt; for n l ~ o coultl possibly have supposed otherwise, unltls.; Ile had the pupal tracheation before hiin as convincing proof? A seco~ld coilsequerice to be noted is that the true basal portion of Its, being fused with N, for almost its whole length, takes on the appe:trance of being actually the sten1 of the media; and this appeararlce is cven nlol-e definite when we

note how closely tlie true steni of the rnedia 1r1 the forewing resembles this Thirdly, M, itself, being fused wit11 R s for such a great part of its length, I~econles quite lost in the irnagii~al venation, except indeed for tlie small vein ascending from nlf to Its, which is, of course, its extrelr~e basal portion. Fourthly, the true main stem of the rnedia in the hindwing (as will be lllore fully seen below) comes into line with the pseudo-cubitus, and forms the basal portion of tha t extraordinarily complex vein.

The course of M, in the hindwing, after i t leaves I?,, is similar

to that iri the forewing, and need not be further discussed. M:, however, from its origin a t mi; follows a consitlera1)ly simpler course than i t does in the forewing. There is no median arculus, and no median loop. Indeed, M, simply run5 parallel to arid below M, for a considerable distance, finally rneetlng M, where i t

drops upon the pseudo-cubitus, and dividing to send two hrsnclles to the wing-border. Thus, instead of two isolatcd separate cells being t:nclosed betweer~ MI and M,, as in tlie forewing, only one elongated cell lies Letweer1 them. I n the imaginal venation, this long cell is divided across the niiddle by e cross tein. The two portions may be called the ,fifil.sf and secor~d intrcc-?rzediul~ cells, wit11 the notation im, and im,, as in the forewing. I t will be noticed that M, in the hindwing forms about twice as large a portion of the pseudo-cubitus as i t does in the forewing.

(3) 7'I~e tvue Cubitus (Cu). -The course of tliis trachea, and of the resulting veins in the imaginal wing, is so different in fole and l~indwirigs tllat these rnust be dealt with separately. 111

the forewing, trachea Cu bends sharply up towards M, quite close to the base. It then runs almost straight to the cubital fork, cut ; wllicl~ lies a t a level half way between the base and mj: Prom CY.L/; Cu, rnns almost straight on until i t mects M, dropping on to tlie pseudo-cubitus; i t then gives off two descend- ing branches, and finally drops to tlle wing border. I n the venation, the basal appro:~ch towards M I)ecomes a fusioil, the bend being excessive. Then follows a nearly straight portion, wl~ich exparlds laterally so as tu appear almost like two veirls runniug side by side for some distarlce from c~d ' (showt~ in Plate x., by a thickening of Clr,) I do uot know tile reason for this, and liave not bcen able to detect anything but tlresingle trachea Cu, in this region of tire pupal wing. The rest of the vein C11, for~ris a portion of the pseudo cubitus, togetller with the tlirec transverse veins dc5cendirrg to the wing-border. Gu, diverges sliglitly from Cu,, and rurrs ill n gentle curve to the wing-border, ending rrp just before tlie most proximal bral~ch of Cu,. 1x1 the venation, two cross-veins connect it, with Cu,, and a short, strong cross-vein desccntls front i t on to 1 8 , just distad from cuj:

Tn the hindwing, Cu is irot fused basally with R1. Tlie 111air1 stem of Cu is shortci~ed, so that cut' comes to lie very close to the base, a t a level proximad to that of ~ n j : From cuj; Cu, runs straigl~t on until i t gives off its irloit proxitnal I)rariul~, wller~ i t performs the extraordinary evolution of arclri~ig up to mcet ML, and so reaches the level of the pseudo-cubitus, of whicli i t no\$

forms a part. I have called the point where the arching begins the second cubital fork (cuf). It is clear that we have in the hindwing a more specialised condition of Cu, than is shown in the forewing, and that i t is correlated with what we may call the shifting of the levels of tlle basal portions of Rs and M dowr~wards in this wing. I n other words, the distal portion of Cu, still plays its part in helping to fonn the pseudo-cubitus, even though the basal part of that vein is no longer formed from Cu (as in the forewing), but from M. Finally, Cu, in the hind- wing is a simple vein leaving Cu a t cld; and connected with 1A basally by a cross-vein. I t s actual appearance is rather as if it belonged to 1A than to Cu.

Just as intra-median cells are formed between the two branches of M, so intm-c~cbital cells are formed between Cu, and Cu,. There are three of these in the forewing, viz., icu,, icu,, icu,, owing to the development of two cross-veins. I n the hind- wing, there is only one narrow undivided cell, icu. The cubital cell (cu) is simple, and lies between the main stems of Cu and 1A.

Having completed our study of the radial sector, the true media, and the true cubitus, we are now in a position to analyhe the complex veins which I have called tlle pseudo-media arrd pseudo-cnbitus respectively. These may be traced out with the aid of Plate x., and the overlying transparency.

Z'he Pseudo-media (M').-In the forewing, this vein arises from 1% near the base. Up to mJ; i t is formed by M; beyond mJ; i t is formed by M, above im,, then by M, and M, united for half a.

cell's length, then by M,, B,, B,, B,, and R, overlapping each other in turn, and finally by B, alone. This last vein forks just before reaching the wing-border. In the hindwing, the pseudo- media lilrewise arises from R close to the babe, but it is formed first of all by Rs for a short distance, then by Rs and M, united, then by B, and M, united, then by R,, B,, B,, and S, overlapping each other in turn, and finally by B, alone, with a distal forking as in the forewing.

The cells formed uboae the pseudo-media between the desccnd- ing I3anksian sectors are four in number in the forewing, three in the hind (omitting tire minute triangle t, which is the remnant

BY ~ t . J. TILLYAHD. 239

of the fourth). These may be termed the uppeq- series of Hanksian cells ( b ) . Tho cells formed below the pseudo-media between these sarne sectors arefour in number in each wing, and may be called the lo?r>er series of Bar~ksion celk (b'). They lie distad from im,.

The Pseudo-cubit~~s ( C u l ) . I n the forewing, this vein is formed basally by the rnain stern of Cu up to cujcJ: It is then continued by Cu,, M,, M,, B,, B,, and B, overlapping each other in turn, anti finally ends on B, alone, with a small distal forking. Tn the h~ndwing, the pseudo-cubitus arises from R, proximad to the origin of M'. It is formed basally by the main stem of M as far as m j then by M, alone, then by M, and Cu, fused for two cells' le~lgth, then by M, alone again for a cell's length, then by M,, M,, B,, B,, and B, overlapping each other in turn, and finally by I%, alone, with a distal forking as in the forewing The cells between i t and the posterior wing-border may be termed the posterzor series of cells ( p).

We are now able to realise how exceedingly con~plex these two apparently sirnple longitudinal veins really are, and how impossible i t would be, by any protracted studies i r ~ the com- parative venation of the imagines of the family and its allies, to arrive :tt the solutiorl which was all tlie tirne re:tdy to our hands, for anyone who cared to take the trouble to obtain the pup% in the right stage. Tliat solution shows us, indecd, that the wing-venation of tlie G'hrysopidm is not only, as Petersen suspectetl, "the most abnormal of all the families," but that it is indeed one of the most abnormal and highly specialised vrna- tions to be found within the Irisecta. Judged from this stand- point, the C'hrysopid~ stand far and away above all other Neu- roptera in the effect and extent of their wing-specialisation.

One point remains to be mentioned in connection with the conlplex veins M' and Uu'. If we compare Text-fig.5 and Plate x i , figs.1-2, with the transparency overlying Plate x., we see that, in order to achieve the imaginal result, the ovev-lapping of tlie Bailksian sectors, one upon another, needs to be much greater than i t is in the pupal wing. I n fact, as seen in Text-fig.5, these do not overlap a t all, but barely meet. How can we explain this? The an9wer is that the overlapping is not present in the

240 STUDIES I N AUSTRALIAN NEUROPlERA, iii.,

freshly formed pupal wing, bu t is formed during the snbseyuer~t ruckir~y of the wing, which begins on the second or third day of pupal life. I n Plate xi., fig.3, 1 photographed the hindwirrg of a pupa of Chrysopa A, nearly three (lays old. Here the trans- verse rucking is plainly to be seen beginning, and the overlapping is already very considerable. I n a pupa four or five days old, the rucks are so great that a photograph is useless. However, the final amount of overlapping iseasily determined by working back from Rs a t the apex of the wing, and counting the number of distal forks (df). Thus in both wings of C. s ignata there are no forks on S, to S,; S, and S, are forked; B,, R,, and I<, are simi- larly forked; B, has a branch as well as a small forb; M, and M, each send two veins to the border, and Cu, three. Counting backwards, therefore, these can all be correctly placed. As the positions of H , to R, on Rs are known also, i t follows that the amount of overlapping of, say, 73, on B,, in order to carry each of these veins from its original level on R s to its final level on the posterior wing-border, must be as shown in the transparency. The result night also have beer] deducetl, with very littlc doubt, from a study of Plate xi., tig.3, alone.

I'he fii.mation of the I'terostiyma. -This peculiar, thickerled, green patch on the wing is not present in all bpecies. I t s forma tion is rather striking. Instead of running along under the pterostigma to form its base, as we rnigl~t rxprct, Sc only penetrates a very short way from the proxirnal end of the patch IIeyond that, a series of srnall tr:tchet-e arises from K, and their ends bend over so as to continue .roughly tlle line alrrch we should have expected Sc to follow. This accourlts for the pre- sence of the cross-veins between Sc and R in the imaginal ena tion. I t also probably explains w11y the pterostigma descends to R in the hindwing, since there is r ~ o continrrous trachea PC inter- posed between R and the costal margin.

The Anal Veins.-In the pupal tracheation there are th, ee distinct anal veins arising somewhat ill a bur~ch bclow Cu. In the forewing, I A is branched; likewise 2A, but tlle proxinral branch descends upon 3A, and appears as a cross-vein in tlle imaginal venation; 3A is- unbranched, but urldergoes a double

BY R . J. TILLYARD. 241

curvature which brings i t into contact with the wing-border between tlie base and the anal angle. I n the hindwing, tlle anal veins are smaller, and quite inconspicuous; 1A and 2A are simple; 3A is short, but sends a small branch to the wing- border above the anal angle I n bot11 wings, 1A is co~l~lected with ('u, by a cross-vein close to its origin; in the forewing, in addition, a short cross-vein connects 1A with 2A.

It seems probable that very satisfactory, constant, specific cl~aracters could, in many cases, be obtained from comparative studies of the anal veins in closely allied species. I<ut the diffei-erlces in the regions of Rs, M', and Cut are so numerous and striking that they sllould illnays be given preference over the diff'erences in the anal region. The following appear to be the venatioual differences on which sound species of Ch??ysopa may be based.

( I ) General shape of wing (breadth, acuteriess or roundness of apcx, etc.).

( 2 ) Forni of the costa and costal area, especially in forewing, where the costa is often arched upwards, as seen in C. sigltnta. Nurnber of costal cross veins.

(3) Presence or absel1c.e of pterostigma; if present, its extent and density; albo thc. 11uml)er and position of the hypostiymatzc cross-veins between Sc and R.

( 3 ) Number of free sectors (e.g., S, to S, in C. s i q ~ ~ n t a ) and of fuseti or Bariksian sectors ( P q., B1 to 13, in C. sigl~ata) given off by lls. Dependent up011 this would be also the number of cells between i { anti Ks, anti tlie rlurnber of upper Banlisian cells ( b ) .

(5) Nurnber of gradate veins irl both inner and outer series. (6) Form of the median loop and arculus: position of distal

ciid of rnl upon M', in relation wit11 the foot of tlie cross-vein deper~dirlg frorrl Rs.

(7 ) Number of closed cells beyond arcul us, in space betweci~ M' arld Cu' in forewing: number of same beyond wdin hindwing.

(8) Number of distal forks (df ); ~ ~ u r n b e r of simple posterior cells (p) i~efore t l ~ e fitst (rnost proximal) distal fo1.k.

(9) DiEererices in the comparatite lengtl~s and widths of t l ~ c three median cells (nz,, m,, m,) in the forewing. Amount of separ;ttion of im, from inz,.

245 STUDIES IN AUSTRALIAN NEUROPTERA, iii.,

(10) Differences in the form of the three intra-cubital cells ( Z C T A ~ , i cu2 , iczc,) in the forewing.

( 11) Differences in the anal region; in particular, the curvature of 3A, and its relationship with the wing-bo~.der.

I t is possible that a careful study of these points might reveal a satisfactory method of siibdividing the genus. No characters which are correlated merely with size (e.g., greater or less num- ber of branches from Rs) can legitimately he used in this con- nection, since species of different sizes are often most closely related.

Phylogeny of the Ghrysopidcr?.

The results obtained in this paper appear to me t,o be sufi- cierltly striking and suggestive to enable us to understand the phylogeny of the Chrysopidcr? along fairly broad lines, if not in every ininute detail. W e are still unable to make the full com- parisons between the scheme of venation in Ch~ysopn, and that of allied groups, because we have not yet obtained the scheme of the pupal tracheation in those groups. For example, i t would be very instructive to compare the Chrysopid venation with that of the Apochrysidtr.. But the pupal tracheation of tlle latter is r~oL known, and indegd is never likely to be discovered, since no larva of t l ~ i s family has yet been found. All we can do is to compare the imaginal venations, using them with the greatest care, and applying stringent tests to our conclusions. T l ~ e same holds good if we dcsire to compare the vcnation of Ghrysopu itself with that of other genera of Chrysop id~ . The nearer the relationship, tlre closer will be the comparison; but we have to reniernber that, so far, no othcr genus except Chrysopa has had its scheme of trachea ti or^ worked out, so tliat this final court of appeal is denicd to us.

It seerris safe to lay dotyn the following rule to enablc us to distinguish a t sight a true media from a pseudo-media, in what- ever wing i t might occur : -The cdpparel~t rnediu?~ vein is a true wzedza fl the bvur~ches oJ' Rs marest the base of the w i ? ~ y do ~ o t descend directly 0 . 1 ~ to it , but r u n lov~git.ud~~ral/y uhove a r ~ d more or less payallel to it. If; however, o m or more of these bru~iches

BY R. J. TILLYARD. 243

descend 71pon the appare~zt nzeriiau veiu,'tlwr~ that vein must be considered to be a pseudo-media.

The same test cannot, of course, be applied to the pseudo- cubitus, the only sure arbiter in this case being the pupal tra- cheation. It seerns, however, inherently probable that the two formations -- pseudo-media and pseudo-cubitus-must go together; since, if the true media is displaced and reduced sufficiently to allow of the formation of a pseudo-media, i t seems almost essen- tial that the true cubitus must suffer displacement and reduction as well.

Text-tig.6.-Forewing and 11as.tl poition of hlndwiny of ail Apochrysltl, Oligochrym grr/elli.c E&. -llet., ( x 4:) for conlparison with that of (Ihry,copn. The nierlian fork ( ? r ~ . f ' ) and the limits of M , and M2 111 the forewlng rrtnnot he el~arly ddeteurninetl.

Applying the above rule to the wing of an Apochi-ysid (Text- fig 6), we see a t once tliat the apparent media rnust be a pseudo- media. Judged, therefore, on this very important point, the Ap~ochrysidn! are true allies of the Chrysopidc~, arid the two groups might perhaps be regarded as subfamilies within the single farnily G'hrysopi(ice. The Apochrysidn! are in many ways so highly specialised, that they cannot be regarded as standing anywhere near the direct line of descent of the 'hrysopidn~. They stand in the same relationship with the Chrysopidw that the genus Psychopsis does to the rest of the 0smyl;idre. There is, in fact, a very obvious convergence of venational pattern between the Apochrysidct! and Psychopsis. 111 both, the wing is broad,

244 STUDIES IN AUSTRALIAN NEUROPTERA, iii.,

with a central "disc" and a broad rim all round it; in both, Sc, It aud Rs unite before the tip of the wing, and the disc is closed distally by a gradate series of cross-veins. All these characters are almost certainly the ?esult of convergence. The only arcl~aic character common to the two groups is the basally-placed origin of Rs in botlr wings. It seems to me that tlre Apock.ysidce lie far off the main line of descent of the C'h?-ysopidm, and that i t is useless to attempt to derive the latter from Apochrysid-like ancestors.

The stages by which the original plan of a true n~edia and cubitas, wit11 branches of Rs running above them, and all more or less parallel (the archaic Osmylid pattern), gave place to the Chrysopid pattern, are quite easily conceived, when i t is rernem- bered that the pseudo-media and pseudo-cubitus are, in reality, for all except the most basal portions of their lengths, true Banksian lines. T t will not be necessary to repeat t l ~ e diagrams given ill No.1 of this series of Studies ( L C . , p.748, Il'ext fig.] O), in wl~icll the forrnation of a Banksian Line in iWyrrnaleo~zlide wa5 contrasted wit11 the formatioil of a Gradate Series in Chry- sopidc(~, and Loth were developed from the archaic Osmylid forma- tion. It is only necessary to unders ta~~d that what we have tiiscovered in this paper io the fact that orlly the tlistul branches of ILs, in Ghrysopu, develop gradate cross-veins, whereas tlre pro.t.imccl branches of Rs clevelop Banksian Lines (R.1' and Cu') and tlrrls behave in the same lnanner as the distal branches of Rs i n the Myrrneleor~tzrlrr,. A combination, then, of the two series of diagrams, for the two portions of the Chrysopid wing, will brir~g about tbe retli~iretl result. I n this connection, we rnigl~t also study with profit the irregular series of cross-veins Letween Its and M' in Oliyocl~ryscc. We must also, of course, allow that, from tile very bcginnirrg, the true rnedia and cubitus Lecame erlcroacl~ed upon by tile branches of its, until they finally rlnderwer~t such reduction and displacement as we now see in Chrysopu.

We rnay postulate, t l~en, for the Clbrysopidre, an ancestral wing-form (Tcxt-fig.7) in wl~ich the radial sector arose close to tile base in both wings, and ran evenly parallel to and u~lder the

BY R. J. TILLYAIID. 245

radius. Sc, 12, and Rs did not unite before the tip of the wing. 'She branches of Its were numerous, and tended to run dowrl- wards obliquely across the wing, rather than to turn and run parallel to and beneath Ks. M was two-branched, as was also u . Both were moderately short, and tended to curie down- wards to the posterior border of the wing, so as to run parallel with the more proxi~nal branches of Rs. Three anal veins were present, all short. The cross-veins between tlie branches of Rs tended to become arranged in series, with elimination of those that were unsuitably placed. Text-fig.: shows a hypothetical ancestral Cl~rysopid wing conceived on these lines.

'I'ext-fig.7.-H~~pc~t11etic~11 srlccstral wing-fol.ur of t h e Cl~~y~lso~~idrv .

Palzontology here conres in, and aEords us valuable proof that our theory of Chrysopid descent has a solid basis of fact. Text-fig.8 sl~ows the wing of Bfesochrysopa zittsli Meunier, fron: the Lithographic Chalk of Bavaria (Upper 3 urassic). This wing was originally described by Meunier as a Termite (genus iLfagenio- termes), but was re-studied and figured by Handlirsch ("Die Fossilen Insekten," p.612, and Plate xlviii., fig.14). This author proposed the generic name Mesoch~ ysopa for it, and placed i t as the unique representative of a new family, Mesochrysopidn~. His comment on tlie character of this family is very instructive, if read in the light of our new knowledge of Chrysopid venation. He says :-" Diese Gruppe bildet zweifellos ein Bindeglied zwischen den Prohemerobiden und Chrysopiden. Mit ersteren hat sie den. nocli ungebrochenen Radius gemeiri," (here he un- doubtedly intended to say " Radial sector" for Hadius"); " mit leteteren die Bildung des Cubitus und der Analadern, sowie die

246 STUDIES IN AUSI'RALIAN NEUROPTERA, iii.,

stufenformigen Queradern zwischen den aes ten des Sector. Die Medialis ist noch ursprunglicher als bei den Chrysopiden, bei welchen sie in fast gerader Richtung dber die Fliigelmitte hinaus fortgesetzt und von einer langeren Reihe viereclciger Zellen begleitet ist." It seems clear, therefore, tha t Handlirsch, if 11e had known the true structure of the media in Chrysopa, would have placed this form considerably closer to the Chrysopida) than he d ~ d

Text-fig.8. -Wii~g of ilfe~ochrysopu zitteli Meunior,( x 2). Litllograpllie chalk, Bavaria. Upper ,larassic. (Adaptctl from Handlirsch).

Tn Text fig.8, 1 have copied Handlirsch's figure, of this inter esting fossil, and have added to i t my own interpretation of the venation. Also, as the wing was figurcd with the apex to the left, I have reversed it, to facilitate corr~parisorr with my other figures. There are evidently twelve branches descending from Rs; these are labelled 8, to S,,. The limits of M, Cu, and the three anal veins are clear enough proximally (thouglr the ex- treme base of the wing is lost), but the actual distal endings are slightly in doubt. What is clear, however, is that both M and Cu are two-branched, and of just about the shape and size pos- tulated in our hypothetical Chrysopid ancestor. Furtl~er, the more proximally placed cross-veins between the branches of R s have begun to arrange themselves into two continuous series, upon which I have placed the labels M' and Cu' respectively, since I consider them to represent the primitive formation of pseudo media +inner gradate series for the upper set, and pseudo- cuhitus + outer gradate series for the lower set respectively. They are still very irregular, and one cross-vein appears to be

BY R. J. TILLYARD. 247

missing between MI and S,,. But such a cross-vein may well have been present, though not visible in the fossil. If so, then M, was already linked lip and in line with M'; if not, a very slight bulging of S,, downwards would give the necessary con- nection. Cu, is already linked up with Cu', though, it mnst be confessed, very irregularly But i t is just from such irregular and unstable forms as this that the most beautiful and perfect venational specialisations often spring.

The condition of M, and M, in this fossil is very interesting, and leads me to suggest that the wing was rt forewing. For there is already a wealc median arculus present between MI and Cu, (at the point where M, leaves M,). Moreover, M, is pecu- liarly curved, so that, of the three elongated cells marked oEby cross-veins between i t and M,, the middle is already the narrow- est. If, therefore, a t the time when M' definitely jlinctioned with M,, a further strengthening were needed, it would only be necessary for t l ~ e middle cell to close completely up, and we should have t l ~ e exact formation found in the forewing of Chrysopa.

The other obvious points in which Mesochrysopu differs from Chrysopu are just sucli as we might expect in an older and more generalised type of wing. The distal veinlets in the costal space are forked, so are the endings of R, Rs, and all its branches. Below Cu', the branches of Rs descend a considerable distance before they reach the wing-border, and are separated by two irregularly-placed rows of cross-veins. These cross-reins must have all disappeared, and the distance between Cu' and thc border must have become considerably lessened, before this por- tion of the wing could take on the true Chrysopid facies. As for the distal forks, quite a considerable number of them remain in CI~rysopa (df in Plate x.), but they have disappeared in the pterostigmatic region, and from the ends of several of the most proximal and most distal of the branches of Rs, leaving only the middle branches forked. We must note also that, in Meso- cl~rysopa, Rs is still "ungebrochenen." The weakly zig-zag course of this vein in C'hrysopu is a well-known form of specialisation, of frequent occurrence- for instance, in the veins of Agrionid

248 STUDIES IN AUSTRALIAN NEUROPTILKA, iii.

Dragonflies. Alternation of straight and weakly zig-zagged longitudinal veins is a very advantageous and specialised arrange- ment, and is developed to perfection in CImysopa, where It is straight, R s zig-zagged, M' straight and Cu' zig-zagged.

We may conclude, then, that Mesochrysopa stood very near, if not actually upon, the line of descent of our recent Chryso- pidre. As this is an Upper Jurassic form, the rise of the true Chiysopidrr: probably began in the Cretaceous, About this time, or perhaps in the Eocene, our present Aphides becan~e dcvcloped (many species are known from t l ~ e 1,ower Oligocene). As the Chrysopid larvze feed upor1 Aphides and sirnilar insects, the evolution of the two groups must have proceeded step by step togetller, until the present intimate association became fully established.

EXl'TJANATION Olp 1'LATIES X., S. / i s , X I . Plates s.-x. his (l'ranspnrency).

r l11e 1 i~nagiual \-enation of Cl~rysopn si!p~at(c. Walker, is s11on~11, muclr enlnrgect, in bleclr, on Plate x. Superimposed upon it, in red, on the trarrspsrency, is a t l iagran~r~~atic sclrerne of tlre pupal tracl~eation, t,o enable the reader to trace tlre intricate f o r n ~ a t i o ~ ~ of tllc pentlo-metlio ant1 pseudo-cubitus.

I A, 2A, HA, the three anal veins-H, - l3,, t,lre four Esnlcsiar~ sectors (-S7-S,,)-h, upper, arrrl h', lower R~znksian calls C ' , oost>~-Ch, cuhitas -Cu,, its npper, Cu,, it,^ lower branch-Uu', pseutlo-cubit,[ls-cic, cahit,al cell-mi; cubitztl fork-elf, secorrrl oul~it,al fork-(@; tlistal forks--g, inner, y', ontt.1. series of gradate reins-icli, intra-ctthititl cell of' hinciwing . . %or, -reri,, the three intrit-cubits1 cells of Porewir~g-iwi , , i ~ n , , first ant1 second int,ra-metliarr cells-M, media-MI, its npper, M,, its lower h~srlclr -MI, pseudo-media-sn,,-~n,, median cells-?nu, median erculus--?nL median fork-snl, median loop (-- "divisory veirllet" of Hanks)-p, pos- terior cells-pt, pterostigma-R, radius-?;ti radial forli-Rs, r:uiial sector -8,-S,,, its branches-Sc, sul.)costa-ne.r, snboostal cross-vei~l--t, minate triitngle (-re~nn:bnt of first upper J3anksian cell i l l 1~indwirrg)-r, false origin of Rs in hinclwirrg.

Plete xi. (Photomicrograplls). Fig. 1 .-'l'raoheation of pupzl wings of Chrysopa sip7,mtn \Valker, ( x 40).

Pupa one (lay old. Fig.2.-Forewing and a small portion of hindwing of same, ( x 66). Fig.3.-Hindwing of pupa of CI~vysopa A, ( x 27) to sllow ruckiny of the

wing. Pupa nearly three clays 01.1.

P.L.S N . S . W . 1918. PL. XI.

Bibliography of the Neuropterida Bibliography of the Neuropterida Reference number (r#): 313 Reference Citation: Tillyard, R. J. 1916 [1916.09.13]. Studies in Australian Neuroptera. No. 3. The wing-venation of the Chrysopidae. Proceedings of the Linnean Society of New South Wales 41:221-248. Copyrights: Any/all applicable copyrights reside with, and are reserved by, the publisher(s), the author(s) and/or other entities as allowed by law. No copyrights belong to the Bibliography of the Neuropterida. Work made available through the Bibliography of the Neuropterida with permission(s) obtained, or with copyrights believed to be expired. Notes: File: File produced for the Bibliography of the Neuropterida (BotN) component of the Global Lacewing Digital Library (GLDL) Project, 2005.