236 DARWINISM chap. 



The most interesting and most conclusive example of 

 warning coloration is, however, fm-nished by caterpillars, 

 because in this case the facts haA'e been carefully ascertained 

 experimentally by competent observers. In the year 1866, 

 when Mr. Darwin was collecting evidence as to the supposed 

 eftect of sexual selection in bringing about the brilliant 

 coloration of the higher animals, he Avas struck by the fact 

 that many caterpillars have brilliant and conspicuous colours, 

 in the production of which sexual selection coidd have no 

 place. We have numbers of such caterpillars in this country, 

 and they are chax'acterised not only by their gay coloiu's but 

 by not concealing themselves. Such are the mullein and the 

 gooseberry caterpillars, the larvse of the spurge hawk-moth, of 

 the bufF-tip, and many others. Some of these caterpillars are 

 wonderfully conspicuous, as in the case of that noticed by 

 Mr. Bates in South America, which was four inches long, 

 banded across with black and yellow, and ^vith. bright red 

 head, legs, and tail. Hence it caught the eye of any one who 

 passed by, even at the distance of many yards. 



Mr. Darwin asked me to try and suggest some explanation 

 of this coloration ; and, ha"ving been recently interested in 

 the question of the Avarning coloration of butterflies, I ^j 

 suggested that this was probably a similar case, — that these 

 conspicuous caterpillars were distasteful to birds and other 

 insect-eating creatures, and that their bright non -protective 

 colours and habit of exposing themselves to view, enabled 

 their enemies to distinguish them at a glance from the edible 

 kinds and thus learn not to touch them ; for it must be 

 remembered that the bodies of caterpillars while groAWng 

 are so delicate, that a Avound from a bird's beak Avould be 

 perhaps as fatal as if they Avere deA^oured.^ At this time not 

 a single experiment or obserA^ation had been made on the 

 subject, but after I had brought the matter before the 

 Entomological Society, tAvo gentlemen, Avho kept birds and 

 other tame animals, undertook to make experiments Avith a 

 A'ariety of cateri^illars. 



Mt. Jenner Weir AA-as the first to experiment AA'ith ten 

 species of small birds in his aviarj^, and he found that none of 

 them Avould eat the folloAving smooth-skinned conspicuous cater- 

 •■ See Darwiu's Descent of Man, i>. 325. , 



