386 SEXUAL SELECTION. [Part II. 



brown, or various tints of dull yellow, or nearly white. 

 In several species the males are much darker than the 

 females, 16 and these belong to groups which generally fly 

 about during the afternoon. On the other hand, in many 

 genera, as Mr. Stainton informs me, the males have the 

 hind-wings whiter than those of the female — of which fact 

 Agrotis exclamationis offers a good instance. The males 

 are thus rendered more conspicuous than the females, 

 while flying about in the dusk. In the Ghost Moth (Ile- 

 pialus hwnuli) the difference is more strongly marked ; 

 the males being white, and the females yellow, with 

 darker markings. It is difficult to conjecture what the 

 meaning can be of these differences between the sexes in 

 the shades of darkness or lightness ; but we can hardly 

 suppose that they are the result of mere variability with 

 sexually-limited inheritance, independently of any benefit 

 thus derived. 



From the foregoing statements it is impossible to ad- 

 mit that the brilliant colors of butterflies and of some few 

 moths have commonly been acquired for the sake of pro- 

 tection. We have seen that their colors and elegant pat- 

 terns are arranged and exhibited as if for display. Hence 

 I am led to suppose that the females generally prefer, or 



16 For instance, I observe in my son's cabinet that the males are 

 darker than the females in the Lasiocampa quercus, Odoncstis potatoria, 

 Hypogymna dispar, Dasychira pudibunda, and Cycnia mendica. In this 

 latter species the difference in color between the two sexes is strongly 

 marked ; and Mr. Wallace informs me that we here have, as he believes, 

 an instance of protective mimicry confined to one sex, as will hereafter 

 be more fully explained. The white female of the Cycnia resembles the 

 very common Spilosoma menthrasti, both sexes of which are white ; and 

 Mr. Stainton observed that this latter moth was rejected with utter dis- 

 gust by a whole brood of young turkeys, which were fond of eating other 

 moths ; so that, if the Cycnia was commonly mistaken by British birds 

 for the Spilosoma, it would escape being devoured, and its white decep- 

 tive color would thus be highly beneficial. 



