PROTECTIVE MIMICRY. 209 



influence of their surroundings : the fish-like form of the 

 whale is more suited to progression through the water ; it is 

 possible that the blindworm can more easily force its way 

 through the tangled stems of a hedge or through dense 

 herbage, owing to its snake-like form. Causes of this kind 

 may possibly have had a share in producing these form re- 

 M'jnblances that are seen in true mimicry. The genus LeptaUs> 

 for example, among the Pieridie, imitates the Helicouidai not 

 only in its colour markings, but also in the form of its wings, 

 departing in both particulars from most of its immediate allies. 

 The similarity of flight between these butterflies, upon which 

 stress has also been laid, is of course a consequence of the similar 

 conformation of the wings. 



If Lcptalis and Euterpe were the only genera of " Whites " 

 which showed this deviation from the normal wing structure 

 .iu. the direction of the Helieonidfe, the assertion that this 

 was due to causes other than natural selection producing a 

 resemblance for the sake of protection, could hardly be sub- 

 stantiated. 



But we have in this countrv a white butterfly the Wood 



t- V 



White, (Leucophasia sinapis) in which the male has the fore 

 wings terminating in a somewhat pointed outer extremity, but 

 in which the female has ova] wings by no means unlike those 

 of various Heliconidee. 



Instances of Developing Mimicry in Butterflies. 



In the genus Leptalis and some allied genera, the bulk of 

 the species not only show a general resemblance to the pro- 

 tected Helicouidfe, but are like particular forms. But there 

 are other examples of mimicry in which one particular species 

 .differs from its congeners, and is coloured after the same 



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