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Show 236 DARWINISM CHAl'. The most interesting and most conclusive example of warning coloration is, however, furnished by caterpillars, because in this case the facts have been carefully ascertained experimentally by competent observers. In the year 1866, when Mr. Darwin was collecting evidence as to the supposed effect of sexual selection in bringing about the brillirmt coloration of the higher animals, he was struck by the fact that many caterpillars have brilliant and conspicuous colours in the production of which sexual selection could have 11~ place. vVe have numbers of such caterpillars in this country, and they arc characterised not only by their gay colours hut by not concealing themselves. Such arc the mullein and the gooseberry caterpillars, the larvro of the spurge hawk-moth of the buff-tip, and many others. Some of these caterpillar · ~rc wo,nderfully. co1,1spicu.ous, a~ in th~ case of that. noticed hy Mr. Bates m South Amcnca., whiCh was four mchcs lon rr banded across with black and yellow, and with brio·ht rc~l head, leg.·, a.ud tail. Hence it caught tho eye of any o0nc who passed by, even at the di stance of many yards. M~'· Darwin. asked me to try and suggest some exphnation of tlus coloratiOn j and, having been recently interested in tho question of the warning coloration of butterflies I suggested that this was probably a similar case,-that these conspicuous caterpillars were di stasteful to birds and other insect-eating creatures, and that their brio·ht non -protective colours and habit of cxposino· thcmsclves 0 to view eu;_thlc(l t~eir enemies to distinguish them at a glance from tl1e edible kmds and thus learn not to touch them j for it must be remembered that the bodies of caterpillars while oTowin <•· are so delicate, that a wound from a bircl's beak wonl<l 1 ,~ perhaps as fn.tal as if they were dcvourcd.1 At this time nol a single experiment or observation had been mtdc on thu snhjcct, but . a.fter I had brought the matter heforc the Entomological .i:)ocicty, two gCJttlemen, who kept hirds and other tame annuals, undertook to make experiments with a variety of caterpillars. ~r. Jenner 'V eir was the first to experiment with ten species of small hirds in hi. aviary, and he found th~Lt none of them would cat the followin g smooth-skinned conspicuous cater- 1 ~ee Darwin's Descent of .Alan, p. 325. IX WARNING COLORATION .AND MIM lORY 237 pillars - Abraxn.s grossulariata, Diloba crorulcocephala, Anthrocera filipcnd ub, and Cucullia vcrbasci. He also found that they would not touch a.ny hairy or spiny larvro, and he was sati. ficd that it was not the ha.irs or the spines but the unpleasant ta. to that ·caused them to be rejected, becau ·c in one case a young smooth larva of a h~tiry species, and in another case the pupa of a spiny hrva, were equally rejected. On the other hn.nd, all green or hrown cn.tcrpillars as well as those that resemble twigs were grec(lily devoured.1 Mr. A. G. Rntlcr also made expm·imcnts with some green lizards (Lacerta viridis), which greedily ate all kinds of food, including flies of many kind ·, spiders, bees, butterflies, n.nd green caterpillars ; but they would not touch the catcrpilhtr of the gooseberry-moth (Abrn.xas gro ·suhriata), or the imago of the burnet-moth (Anthroccm filipcndula). The same thing happened with frogs. 'When the gooseberry caterpillars were first given to them, "they sprang forward and licked them eagerly into their months j no sooner, however, had they done so, than they seemed to become awn.re of the mistake that they had made, and sat with gapina mouths, rolling their tongues about, until they had got quit of the nauseous morsels, which seemed perfectly uninjured, and walked off as briskly as ever." Spiders seemed eqnally to dislike them. This ancl another conspicuous caterpillar (Halia wavaria) were rejected by two species-the geometrical garden spider (Epeira di:ulcma) and a hunting spid cr.2 Some further experiments with lizards were made by Professor W cismann, quite confirming the previous observations j and in 1886 Mr. E. B. Poulton of Oxford undertook a considerable series of experiments, with many other specie of Jarvro and fresh kinds of lizards and frogs. Mr. Poulton then reviewed the whole subject, incorporatino· all recorded facts, as well as some additional ohservn.tions made by Mr. J cnner 'Vei r in 1886. More than a hundred species of larvro or of perfect insects of various orders have now been made the snhj ct of experiment, and the r esults completely confirm my original suggestion. In almost every case the protectively coloured larvre have been greedily eaten by all kinds of insectivorous 1 Transactions of the Entomological Society of Loudon, 1869, p. 21. ~ Ibid., p. 27. |