GENERAL CONCLUSIONS 



125 



feed openly on the leaves of the food plant. The larval environment is quite different, and 

 yet the resemblance between the perfect insects is extremely close. Difhcult as these cases 

 are under a theory of external causes, they are as nothing to cases of mimicry between 

 different orders of insects, where there is no such thing as even approximate similarity of 

 environment in the larval stages, since many of the flies which so closely imitate Hymenoptera 

 subsist in their early stages on putrefying organic matter. In view of the frequency with 

 which sexually dimorphic mimicry is developed, any theory based on the influence of environ- 

 ment must presuppose that such influence acts differentially on the two sexes. The case 

 of P. eurytiis and P. epaea would comply with such a view, were it not that we are at once 

 faced with the difficulty that both sexes of E. phegea mimic the female P. epaea. Again, in 

 West Africa the female of the sexually dimorphic Mimacraea fulvaria mimics the male of 

 Acraea alciope. If external causes produce mimicry they must either affect both sexes alike 

 or at least they must affect similar sexes. The above instances show that they do neither. 

 As has been pointed out in an earlier portion of the work, the resemblance between certain 

 Neotropical butterflies is brought about by the transparency of their wings. This transparency 

 has been shown to be produced in a great variety of ways. If external or internal causes can 

 produce resemblance, then those causes must be uniform and must produce their effect by 

 uniform means. The mimicry of these transparent butterflies is evidently not produced 

 by such influences. Finally, it is a coincidence of more than ordinary peculiarity that these 

 supposed all-powerful environmental influences should exert their forces only to produce 

 such resemblances as will cause their possessors to be mistaken for creatures which are 

 nauseous to the palates of their enemies, or which possess stings or other offensive or 

 defensive attributes. 



It is to be observed that few of those who find a difficulty in accepting existing theories 

 concerning the mimicry of one butterfly by another, experience any difficulty in recognizing 

 the numerous other forms of mimetic resemblance which are found in nature — the resem- 

 blance of butterflies to leaves, of caterpillars to twigs, of harmless insects to those of other 

 orders protected by defensive qualities. And yet, provided it can be shown, and the proofs 

 are ample, that an insect is avoided owing to inedible qualities, what can be more natural 

 than that resemblance to that insect should provide a measure of protection. If such a creature 

 as a mantis can so far depart from its normal form as to resemble nothing so much as an 

 animated" vegetable, if an insect of one order can resemble another of a different order 

 characterized by immense differences of structure, how much more easily may one butterfly 

 come to resemble another, since half the difficulty is already surmounted by the similarity 

 of form due to the possession of features which are common to the members of its own order. 

 It should be recognized that mimicry between butterflies is not a thing apart, an exceptional 

 phenomenon without parallel, but is merely another manifestation of a process of nature 

 which is illustrated by many varying examples, all of which may be included under the 

 general term mimicry, and all tending by various means to preserve the species involved. 



In these pages I have endeavoured to give a concise account of butterfly mimicry and 

 the considerations which have arisen therefrom. I should be the last to assert that any finality 

 has been reached in the study of this fascinating subject. Indeed it is only now beginning 

 to be understood, and whilst I have supported the theories which in the present state of our 

 knowledge seem best adapted to the facts, I realize that there are still many difficulties, for 

 the elucidation of which further study and experiment is required. It is my cherished hope 

 that, with the present work as a guide, collectors and naturalists, especially those abroad, 

 will find an additional interest in the study of the bionomics of butterflies. There remains 



