30 Colouration in Animals and Plants. 



purposes that colouration, and, especially, decoration, can alone 

 subserve 1 We can only conceive it of use in three ways : first, as 

 protection from its enemies ; second, as concealment from its prey ; 

 third, as distinctive for its fellows. To the third class may be 

 added a sub-class — attractiveness to the opposite sex. 



The first necessity would seem to be distinctness of species ; for, 

 unless each species were separately marked, it would be difficult for 

 the sexes to discriminate mates of their own kind, in many 

 instances; and this is, doubtless, the reason why species are differ- 

 ently coloured. 



But protective resemblance, as in Kallima* the Leaf-butterfly, and 

 mimicry, as in D. niavius and P. meropej sometimes so hide the 

 specific characters that this process seems antagonistic to the prime 

 reason for colouration, by rendering species less distinct. Now, 

 doubtless, protective colouring could not have been so wonderfully 

 developed if the organ of sight ivere the only means of recognition. But 

 it is not. Animals possess other organs of recognition, of which, as 

 everyone knows, smell is one of the most potent. A dog may have 

 forgotten a face after years of absence, but, once his cold nose has 

 touched your hand, the pleased whine and tail-wagging of recogni- 

 tion, tells of awakened memories. Even with ourselves, dulled as 

 our senses are, the odour of the first spring violet calls up the past; 

 as words and scenes can never do. What country-bred child forgets 

 the strange smell of the city he first visits ? and how vividly the 

 scene is recalled in after years by a repetition of that odour ! 



But insects, and, it may be, many other creatures, possess sense 

 organs whose nature we know not. The functions of the antennae 

 and of various organs in the wings, are unknown ; and none can 

 explain the charm by which the female Kentish Glory, or Oak 

 Egger moths lure their mates. You may collect assiduously, using 

 every seduction in sugars and lanterns, only to find how rare are 

 these insects; but if fortune grant you a virgin female, and you 

 cage her up, though no eye can pierce her prison walls, and though 

 she be silent as the oracles, she will, hi some mysterious way, attract 

 lovers ; not singly, but by the dozen ; not one now and another in 

 an hour, but in eager flocks. Many butterflies possess peculiar 

 scent-pouches on their wings, and one of these, a Danais, is 

 mimicked by several species. It is the possession of these additional 

 powers of recognition that leaves colouration free to run to the 



* PI. I., Pigs 1-3. f PI. II., Figs. l-:j. 



