204 TROPICAL NATURE, AND OTHER ESSAYS. 



of his theory of conscious sexual selection is, that 

 throughout the whole animal kingdom the males are 

 usually so ardent that they will accept any female, 

 while the females are coy, and choose the handsomest 

 males, whence it is believed the general brilliancy of 

 ma,les as compared with females has arisen. 



Perhaps the most curious cases of sexual difference 

 of colour are those in which the female is very much 

 more gaily coloured than the male. This occurs most 

 strikingly in some species of Pieris in South America, 

 and of Diadema in the Malay islands ; and in both 

 cases the females resemble species of the uneatable 

 Danaidae and Heliconidse, and thus gain a protec- 

 tion. In the case of Pieris pyrrha, P. malenka, 

 and P, lorena, the males are plain white and black, 

 while the females are orange, yellow, and black, and so 

 banded and spotted as exactly to resemble species of 

 Heliconidae. Mr. Darwin admits that these bright 

 colours have been acquired for protection ; but as 

 there is no apparent cause for the strict limitation of 

 the colour to the female, he believes that it has been 

 kept down in the male by its being unattractive to her. 

 This appears to me to be a supposition opposed to the 

 whole theory of sexual selection itself. For this theory 

 is, that minute variations of colour in the male are 

 attractive to the female, have always been selected, and 

 that thus the brilliant male colours have been produced. 

 But in this case he thinks that the female butterfly had 

 a constant aversion to every trace of colour, even when 

 we must suppose it was constantly recurring during 

 the successive variations which resulted in such a mar- 

 vellous change in herself. But the case admits of a 



