Chap. XL BUTTERFLIES AND MOTHS. 403 



Islands, males are frequently found which closely 

 resemble the females. In a future chapter I shall have 

 occasion to shew that the beautiful eye-like spots or 

 ocelli, so common on the wings of many Lepidoptera, 

 are eminently variable. 



On the whole, although many serious objections may 

 be urged, it seems probable that most of the species of 

 Lepidoptera which are brilliantly coloured, owe their 

 colours to sexual selection, excepting in certain cases, 

 presently to be mentioned, in which conspicuous colours 

 are beneficial as a protection. From the ardour of the 

 male throughout the animal kingdom, he is generally 

 willing to accept any female ; and it is the female which 

 usually exerts a choice. Hence if sexual selection has 

 here acted, the male, when the sexes differ, ought to be 

 the most brilliantly coloured ; and this undoubtedly is 

 the ordinary rule. When the sexes are brilliantly co- 

 loured and resemble each other, the characters acquired 

 by the males appear to have been transmitted to both 

 sexes. But will this explanation of the similarity and 

 dissimilarity in colour between the sexes suffice ? 



The males and females of the same species of butterfly 

 are known 20 in several cases to inhabit different stations, 

 the former commonly basking in the sunshine, the latter 

 haunting gloomy forests. It is therefore possible that 

 different conditions of life may have acted directly on 

 the two sexes ; but this is not probable, 21 as in the adult 

 state they are exposed during a very short period to 

 different conditions ; and the larvae" of both are ex- 

 posed to the same conditions. Mr. Wallace believes 



20 H. W. Bates, 'The Naturalist on the Amazons/ vol. ii. 1863, 

 p. 228. A. E. Wallace, in ' Transact. Linn. Soc' vol. xxv. 1865, p. 10. 



21 On this whole subject see ' The Variation of Animals and Plants 

 under Domestication,' vol. ii. 1868, chap, xxiii. 



2 d 2 



