J 56 A BOOK OF INSECTS 



it distasteful to the majority of its enemies, and in the 

 second place that the habits of the supposed mimic are 

 such as will enable it to share the model's immunity. 



Not infrequently the sexes of a butterfly differ so 

 remarkably in colour and pattern that the casual observer 

 would certainly mistake them for distinct species ; and 

 when this is the case with a distasteful butterfly that has 

 become a model for mimicry, the respective types of 

 colouring are sometimes reproduced with the utmost 

 fidelity by the males and females of the mimic. There 

 are other instances in which only the female of a species 

 is mimetic, the male retaining the normal colours of its 

 ancestry; while a single species may have two or more 

 distinct forms of female, each coloured in imitation of 

 a separate evil-tasting model. This is explicable on the 

 grounds that the females are comparatively slow in flight, 

 and are exposed to dangers from which the males are 

 exempt — as when they are engaged in egg-laying ; while 

 when there are several forms of female to a given species, 

 each mimicking a different model, we have a clear case of 

 divided risks, the advantages of which are too obvious to 

 call for emphasis. One of the most interesting instances 

 of this kind is shown on Plate XXIY. The butter- 

 fly (Hypolimnas misippus) is not distantly related to our 

 purple emperor. Its headquarters are in India, but it has 

 a wide range in the Eastern Hemisphere. The common 

 form of the female is bright tawny, edged with black, 

 with a conspicuous band of white in each fore-wing. It 

 is a wonderfully exact copy of a much-mimicked Danaine 

 butterfly called Limnas chrysippus — perhaps the most 

 dominant of all Eastern insects — which is common all 

 over Southern Asia and Africa. There are numerous 

 closely allied forms, whether constant local varieties or 

 actual species is not definitely known. Now the geogra- 



