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Show 238 DARWINISM OlJAl'. animals, while, in the immense majority of cases, th~ conspicuous, hairy, or brightly coloured larvre have ?een.r?J.ected by some or all of them. In so~e insLances the. med1b1hty of the larvre extends to the perfect msect, bn~ not m others. ln the former cases the perfect insect is usually adorneJ with conspicuous colours, as the bumet and ragwort moths ; hut in the case of the hnff-tip, the moth resembles a broken piece of rotten stick, yet it is partly inedible, hein(l' refused by ] izards. It i , however, very doubtful whether these arc its chief enemies, and its protective form and colour may ho needed ag;tinst insectivorous bird. or mammals. Mr. Sanmol II. Rcudder, who has larcre]y bred North American butterflie , has found so many of the egcrs and larva• destroyed by hymenopterous and dipterous parasite that hc• thinks at least nine-tenths, perhaps a 0 '1' ater proportion, never reach maturity. Yet he has never found any evidence tha1 snch para.sites attack either tho egg or the larva of the inecli hl(~ Dn.nais archippus, so th<tt in this case tho insect is dist<~s tefn l to its mo.-t dangerous foes in all the stages of its existence, a fact which serves to explain its greu,t abundance and i1H extension over almost tho whole world.l One case has been found of a protectively coloured lar va, -one, moreover, which in all its h<tbit. shows that it trusts to conceu,lment to escape its enemie. -which was yet always rejected by lizards after they had seized it, evid cnt,Jy under the impression that from its colour it woul(l lle eatable. This is the caterpillar of the very common moth Mania typica; and Mr. Poulton thinks that, in this case, tho unpleasant taste i. an incidental ro. ult of SOJllO i)hysiologic:d processes in the organism, and is itHclf a merely nselcs:-; character. It is evident that the insect ·would not conce;ll itself so carefully as it docs if it had not some cncmie., n11<l these arc probably birds or small mamm;tls, as itH food phn1i'i arc said to be dock and willow-herb, not suggest i \'C of pla<'<'i'i frequented by lizards; aml it has been fonncl hy expcrim<'nt that lizards and birds have not always tho S<tmc lik('s and dislikes. The case is intorestino·, bccau ·c it sh o\I'S tl tat nauseous fluids sometimes occur sporadically, n.nd m;ty Llnts lw intensified by natural selection whcll rc<rnircd for 1ltc pmposc 1 Natu1·e, vol. iii. p. 147. IX W ARNIN<i COLORATION AND MIM ICR \' 239 of protection. Another exccptiomd c:vc is that of tl~e ve:·y conspicuow:; catm-pillar of tlte spmgc hawk-moth (Dmleph1la euphorhim), whi<.:h was a.t once eaten hy a liz:ard, although, as it expo ·es itself on its foo<l-phnt in the daytime a.nd i~ :cry abundant in . om localiLi •s, it mtL t almost certainly lle dislllcccl hy birds or lJy some aninml.· who would otherwise devour it. If disturbed while feeding it i: s:tid to tum romHl with fnry :tnd eject a qnantit.y of crrcen litluid, of an acid n.nd diHagreeahle smell similar to th;tt of the spnrgc milk, only wm·sc.l These facts, and Mr. Poulton'H evidence that some larva. rejected by lizard. at fir.'L will he c;tten if the lizards n.re very hungry, show th:tt there r~re clifl'<·ren ·cs in the amonnt of the distastefulneHs, and 1·endcr it proh:t.bl tl1:tt if other food were wantincr many of the. e conspi('tlOttH ins('cts wonld h' eaten. It is th~ <thnnd;ulce of the cat:d,Je kind. tlmt (J'ivcs value to tho ineclibility of the sma.ll •r nttmher j :tnd this i. prolmbly the rca:on why so nmny ins 'CLH rely on protettivc eolonring rather than on the acquisit.iou of any kind of defm1sivc wen.vons. In Lhe long nm the powers of attack and defence must balance C<tch other. Ilence we sec that even the powerful stings of bees and wasps only protect them <tgain:t some enemies, since a tribe of bird. , tho heo -e:tters, have been developed which feed upon them, and some frogs and lizards do so occ<1Sionally. The precc<ling outline will sufficiently ex1~lain the ?haractcristics of "warning coloru.tion" and the end Jt serves m natm:c. There arc many other curious modifications of it, but these w11l be best appreciated after we have di. cussed the rCI~;trka hle phenomenon of "mimicry," which i hound np w1th <tnd altogether depends npon "wamil!O' colour," n.nd. is in some cases the chief indication we h<tve of the possess10n of some ofl'ensive weapon to sccme the safety of the species imitated. Mim.itry. This term has been given to a form of protective re. I~hla. nce, in which one species so closely resembles another m external form and colourino· as to be mistaken for it, <dthongh the two may not be really ballied and often bclm1g to distin<.:t 1 SLainton's Nwn,rd nj 1Jutlf'1:/lies awl .ltfoths, vol. i. p. 93; E. B. Po'ulton, P1·oceedinys of the Zoot. Soc. of Lundur~, 1887, l'P· 191-274. |
