230 SEXUAL DIMORPHISM 



fact is not considered of much importance by those who have 

 endeavoured to explain mimicry by selection, and when botli 

 sexes are alike its importance is not so evident. But when 

 the two sexes are remarkably different, its importance is 

 easy to perceive. For, supposing similar variations occurred 

 in the two sexes, then there is no reason why the selection 

 in the two cases should not be the same. A variation tending 

 to disguise would confer the same protection wherever it 

 was found. 



It may be suggested that in one sex survival depended on 

 a different character, which conferred an advantage in the 

 habits of that sex, but not in the conditions of life of the 

 other. For instance, this suggestion is made in reference to 

 another case of mimicry among the Indian butterflies from 

 Col. Swinhoe's collection in the hall of the Museum at South 

 Kensington. This case is as follows : Lcertes pammon has 

 two forms of female, one mimicking Menelaides aristolochce, 

 the other M. hector. The male of Lcertes pammon, which 

 differs from the females and is not mimetic, is stated to be 

 very active and thus able to " protect itself," an expression 

 which evidently means to escape from its enemies. This 

 male is also stated to be eagerly devoured by birds, lizards, 

 etc., when caught. Menelaides aristolochce and its allies are 

 stated to be distasteful and not generally devoured. A curious 

 fact about this case is that all the species mentioned belong 

 to the same family, the Papilioninae. 



Now in spite of the activity of the male of Lcertes pammon, 

 it is evident that variations of it approximating to the dis- 

 tasteful species would have a still better chance of survival 

 than those individuals which were only active and not 

 modified. Thus if selection were the only factor, some 

 modification of the male would be produced. "We must 

 conclude therefore that the required variations only occurred 

 in the female, and not in the male. That being the case, we 





