ON THE VARIATION OF INSECTS. O 



C. eiirytheme pallida, ? , Ckll. C. philodice alba, ? , auctt. sp. 

 jMnynaid. C. electra 2)(dlida, ? , Grahauistown, Proc. S. Lend. 

 Ent. Soc, 1886, 60. Papilio turnus glaucus, ? , L. Pamphila 

 zahulon pocahontas, 2 , Scudd. Callidryas senncs pallida, ? ; 

 dirty whitish yellow (French, 'Butt, of E. N. Amer.'). — These 

 are all dimorphic female forms, and I think, however looked 

 at, their interest cannot be exaggerated. The first question 

 that arises is. Are they atavisms ? Do they represent the 

 primitive condition of the species ? This at first sight appears 

 not very improbable, but I think we may answer it in the 

 negative. It is not altogether impossible that reversion to the 

 type should be confined to the female, yet it is, I imagine, some- 

 what unlikely ; but what seems to weigh most against the theory 

 of atavism is, that certain species of Papilio are trimorphic in the 

 female sex, and these, at any rate, obviously cannot be explained 

 by atavism. 



Now we have seen above, under " light and dark forms," 

 that some measure of dimorphism may obtain apparently without 

 the slightest reference to sex, climate, or food, of which Hydroecia 

 and Anomis are good examples ; and we shall see below that 

 characters peculiar to the one sex, occasionally appear in the 

 other ; that is to say, one sex, in very rare instances, presents a 

 dimorphic form similar to that which is normal with the other. 

 Suppose, then, a " spontaneous" (that is to say, without reference 

 to general external circumstances) variation to occur, as it is I 

 think certain that they do occur, is it unreasonable to suppose that 

 it might become, either from sexual selection or from physio- 

 logical causes, more prevalent in the one sex than the other ? 

 Further, might it not gradually become peculiar to the sex, until 

 it was the normal condition ? This seems to me the explanation 

 of secondary sexual characters in the Lepidoptera, if not in all 

 other organisms ; and I regard the pale females of Colias and 

 Callidryas sennce, and the dark female of Papilio tiLriim, as fore- 

 runners of what is in the future to be the typical female of each 

 respective species. In one case at least, this final process can be 

 traced. The male of Callidryas semice. is clear lemon-yellow, 

 while the female is either of the same colour as the male, or of a 

 dirty whitish yellow colour. In C. agarithe, the male is clear 

 light orange, while the orange form of the female having appa- 

 rently become extinct, the typical colour of that sex is dirty 

 whitish yellow, like the dimorphism of C. sennce. 



Lyccena pseudargioliis {violacea) nigra, $ , Edw. Lycana 

 hellargus nigra, S , Proc. S. Lond. Ent. Soc, 1886, 61. — These 

 are cases of dimorphism in the male, a rare condition. Maynard 

 states that black females of L. pseadargiolus are occasionally 

 found, so this condition would seem not to be strictly peculiar to 

 the one sex. 



