in PROTECTIVE RESEMBLANCES AMONG ANIMALS 59 



many cases be sufficient for it to lay a quantity of eggs and 

 leave a numerous progeny, many of which would inherit 

 the peculiarity which had been the safeguard of their parent. 



Now, this hypothetical case is exactly realised in South 

 America. Among the white butterflies forming the family 

 Pieridse (many of which do not greatly differ in appearance 

 from our own cabbage butterflies) is a genus of rather small 

 size (Leptalis), some species of which are white like their 

 allies, while the larger number exactly resemble the Heli- 

 conidse in the form and colouring of the wings. It must 

 always be remembered that these two families are as absolutely 

 distinguished from each other by structural characters as are 

 the carnivora and the ruminants among quadrupeds, and that 

 an entomologist can always distinguish the one from the 

 other by the structure of the feet, just as certainly as a 

 zoologist can tell a bear from a buffalo by the skull or by a 

 tooth. Yet the resemblance of a species of the one family to 

 another species in the other family was often so great, that 

 both Mr. Bates and myself were many times deceived at the 

 time of capture, and did not discover the distinctness of the 

 two insects till a closer examination detected their essential 

 differences. During his residence of eleven years in the 

 Amazon valley, Mr. Bates found a number of species or 

 varieties of Leptalis, each of which was a more or less exact 

 copy of one of the Heliconidse of the district it inhabited ; 

 and the results of his observations are embodied in a paper 

 published in the Linncean Transactions, in which he first ex- 

 plained the phenomena of " mimicry " as the result of natural 

 selection, and showed its identity in cause and purpose with 

 protective resemblance to vegetable or inorganic forms. 



The imitation of the Heliconidae by the Leptalides is 

 carried out to a wonderful degree in form as well as in 

 colouring. The wings have become elongated to the same 

 extent, and the antennae and abdomen have both become 

 lengthened, to correspond with the unusual condition in 

 which they exist in the former family. In coloration there 

 are several types in the different genera of Heliconidae. The 

 genus Mechanitis is generally of a rich semi-transparent 

 brown, banded with black and yellow ; Methona is of large 

 size, the wings transparent like horn, and with black trans- 



