408 SEXUAL SELECTION. Part II. 



in comparison with the species having brightly-coloured 

 males. On the other hand, as bright colours are sup- 

 posed to be highly serviceable to the males in their 

 love-struggles, the brighter males (as we shall see 

 in the chapter on Birds) although exposed to rather 

 greater danger, would on an average procreate a greater 

 number of offspring than the duller males. In this 

 case, if the variations were limited in their transmission 

 to the male sex, the males alone would be rendered 

 more brilliantly coloured ; but if the variations were 

 not thus limited, the preservation and augmentation of 

 such variations would depend on whether more evil was 

 caused to the species by the females being rendered 

 conspicuous, than good to the males by certain indivi- 

 duals being successful over their rivals. 



As there can hardly be a doubt that both sexes of 

 many butterflies and moths have been rendered dull- 

 coloured for the sake of protection, so it may have 

 been with the females alone of some species in which 

 successive variations towards dullness first appeared 

 in the female sex and were from the first limited in 

 their transmission to the same sex. If not thus limited, 

 both sexes would become dull-coloured. We shall 

 immediately see, when we treat of mimickry, that 

 the females alone of certain butterflies have been ren- 

 dered extremely beautiful for the sake of protection, 

 without any of the successive protective variations 

 having been transferred to the male, to whom they 

 could not possibly have been in the least degree injuri- 

 ous, and therefore could not have been eliminated 

 through natural selection. Whether in each particular 

 species, in which the sexes differ in colour, it is the 

 female which has been specially modified for the sake 

 of protection ; or whether it is the male which has been 

 specially modified for the sake of sexual attraction, the 



