590 SEXUAL SELECTION. [Part IL 



other species are extremely variable, the males being 

 nearly constant. As I have before mentioned the Ghost 

 Moth {Ilepialus humuli) as one of the best instances in 

 Britain of a difference in color between the sexes of 

 moths, it may be worth adding 19 that, in the Shetland 

 Islands, males are frequently found which closely resem- 

 ble the females. In a future chapter I shall have occasion 

 to show that the beautiful eye-like spots or ocelli, so com- 

 mon on the wings of- many Lepidoptera, are eminently 

 variable. 



On the whole, althouga many serious objections may 

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

 Lepidoptera which are brilliantly colored, owe their col- 

 ors to sexual selection, excepting in certain cases, pres- 

 ently to be mentioned, in which conspicuous colors are 

 beneficial as a protection. From the ardor of the male 

 throughout the animal kingdom, he is generally willing to 

 accept any female ; and it is the female which usually ex- 

 erts a choice. Hence, if sexual selection has here acted, 

 the male, when the sexes differ, ought to be the most 

 brilliantly colored ; and this undoubtedly is the ordinary 

 rule. When the sexes are brilliantly colored and resem- 

 ble each other, the characters acquired by the males ap- 

 pear to have been transmitted to both sexes. But will 

 this explanation of the similarity and dissimilarity *n 

 color between the sexes suffice ? 



The males and females of the same species of butterfly 

 are known 20 in several cases to inhabit different stations, 



strictly intermediate between two other well-marked female varieties, is 

 given by Mr. Wallace. See also Mr. Bates, in c Proc. Entomolog. Soc. 

 Nov. 19, 1866, p. xl. 



19 Mr. R. MacLachlan, ' Transact. Ent. Soc' vol. ii. part 6th, 3d series, 

 1866, p. 459. 



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

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



