THE FACTOKS OF EVOLUTION 167 



We have already heard that the large feline carnivores of the 

 Tropics the tiger, lion, jaguar, leopard, etc. possess a ' sym- 

 pathetic coloration' which is thought to facilitate their approach 

 to their prey, the gazelle, antelope, giraffe, zebra, etc., which on 

 their part appear to be protected by means of a similar colour- 

 adaptation. This sounds very plausible, but it may be objected 

 that all cats hunt their prey chiefly in the dark, during the night 

 when not only cats but all other animals are grey, and even 

 the most perfect protective coloration becomes useless both to 

 them and to their prey. Moreover, it is generally the sense of 

 hearing which is better developed in cats than the sense of sight, 

 and they rely, therefore, in the search for prey, chiefly upon their 

 acute hearing. Other carnivores make still less use of their eyes, 

 and track their prey by the scent. Here, too, protective colouring 

 is of no advantage. 



As regards the protective resemblance of insects, it cannot be 

 denied that there is a ' purpose ' in their coloration, but 

 here, as elsewhere, we must be on our guard against an exaggera- 

 tion of its biological importance. If, as is generally believed, 

 the adaptation really granted such enormous advantage over 

 the species not so furnished, how is it that the latter have 

 not been exterminated in the struggle for existence ? We should 

 at least expect to see the ' protected ' species far exceeding 

 in distribution and number of individuals the ' unprotected ' 

 species, an assumption which is flatly contradicted by everyday 

 facts. We need only think of the Pieridse and Vanessidse at 

 home. Further, everyone who has collected caterpillars, butter- 

 flies, and beetles knows how soon the eye becomes accustomed 

 to discover even the most perfectly adapted insects in their 

 protective surroundings, and we may be sure that their animal 

 enemies, whose senses are usually much keener than ours, 

 cannot be deceived by a superficial resemblance. Moreover, 

 how can we explain these cases in which one species mimics 

 a species living in a far-distant land? A convincing instance 

 is related by Aigner-Abafian concerning the Brazilian butterfly 

 Semnia auritalis, which is a perfect copy of Caryatis viridis, 

 which lives in the Cameroons, and is only very distantly related. 

 It is plain that we have here to do with an accidental similarity ; 

 not by any means an improbable explanation, considering the 



