rilOTECTlVE JIDIICKY. 209 



influence of their surroundiags : 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- 

 semblances that are seen in true mimicry. The genus Lcptalis, 

 for examitle, among the Pieridje, imitates the Heliconidse 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 Leptalis and Euterpe were the only genera of " Whites " 

 which showed this deviation from the normal wing structure 

 in the direction of the Heliconidfe, 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. 



Bnt we have in this country a white butterfly — the Wood 

 White {Lfucophaxia ghiujiis) — in which the male has the fore 

 wings terminating in a somewhat pointed outer extremity, but 

 in which the female has oval wings by no means unlike those 

 ■of various Heliconida\ 



Instances of Developing Mimicry in Butterflies. 



In the senus Leptalis and some allied genera, the bnlk of 

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

 tected Heliconidte, but are like particular forms. Bnt there 

 are other examples i>f mimicry in which one particular species 

 ■difters from its congeners, and is coloured after the same 



14 



