Chap. XL] BUTTERFLIES AND MOTHS. 389 



the more beautiful females Lad been continually preferred, 

 it is almost certain, from the colors of butterflies being so 

 frequently transmitted to one sex alone, that the females 

 would often have been rendered more beautiful than their 

 male partners. But this does not occur except in a few 

 instances ; and these can be explained, as we shall pres- 

 ently see, on the principle of mimicry and protection. 



As sexual selection primarily depends on variability, a 

 few words must be added on this subject. In respect to 

 color there is no difficulty, as any number of highly-varia- 

 ble Lepidoptera could be named. One good instance will 

 suffice : Mr. Bates showed me a whole series of specimens 

 of Papilio sesostris and childrence / in the latter the males 

 varied much in the extent of the beautifully-enamelled 

 green patch on the fore-wings, and in the size of the white 

 mark, as well as of the splendid crimson stripe on the 

 hind-wings; so that there was a great contrast between 

 the most and least gaudy males. The male of Papilio 

 sesostris, though a beautiful insect, is much less so than 

 P. childrence. It likewise varies a little in the size of the 

 green patch on the fore-wings, and in the occasional ap- 

 pearance of a small crimson stripe on the hind-wings, bor- 

 rowed, as it would seem, from its own female ; for the fe- 

 males of this and of many other species in the JEneas 

 group possess this crimson stripe. Hence, between the 

 brightest specimens of P. sesostris and the least bright of 

 P. childrence, there was but a small interval ; and it was 

 evident that, as far as mere variability is concerned, there 

 would be no difficulty in permanently increasing, by means 

 of selection, the beauty of either "species. The variability 

 is here almost confined to the male sex ; but Mr. Wallace 

 and Mr. Bates have shown 18 that the females of some 



18 Wallace on the Papilionidse of the Malayan Region, in ' Transact. 

 Linn. Soc.' vol. xxv. 1865, pp. 8, 30. A striking case of a rare variety, 



