181 THE MALAYAN PAPILIONIDJE AS 



A, B,) has acquired exactly the same peculiarity of 

 having red spots instead of yellow. Lastly, in the 

 island of Timor, the female of P. (Enomaus (a species 

 allied to P. Memnon) resembles so closely P. Liris 

 (one of the Polydorus-group), that the two, which 

 were often seen flying together, could only be distin- 

 guished by a minute comparison after being captured. 



The last six cases of mimicry are especially instruc- 

 tive, because they seem to indicate one of the pro- 

 cesses by which dimorphic forms have been produced. 

 When, as in these cases, one sex differs much from 

 the other, and varies greatly itself, it may happen 

 that occasionally individual variations will occur having 

 a distant resemblance to groups which are the objects 

 of mimicry, and which it is therefore advantageous to 

 resemble. Such a variety will have a better chance of 

 preservation ; the individuals possessing it will be mul- 

 tiplied ; and their accidental likeness to the favoured 

 group will be rendered permanent by hereditary trans- 

 mission, and, each successive variation which increases 

 the resemblance being preserved, and all variations 

 departing from the favoured type having less chance 

 of preservation, there will in time result those singular 

 cases of two or more isolated and fixed forms, bound 

 together by that intimate relationship which consti- 

 tutes them the sexes of a single species. The reason 

 why the females are more subject to this kind of 

 modification than the males is, probably, that their 

 slower flight, when laden with eggs, and their exposure 

 to attack while in the act of depositing their eggs 



