v COLOURS OF ANIMALS 373 



ing in the female may lead to more contrasted markings. 

 Mr. Darwin thinks that here the males have selected 

 the more beautiful females ; although one chief fact in 

 support 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 males 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 Danaidse and Heliconidse, and thus gain a 

 protection. 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 marvellous change in herself. But the case admits of 

 a much more simple interpretation. For if we consider the 

 fact that the females frequent the forests where the Heli- 

 conidse abound, while the males fly much in the open and 

 assemble in great numbers with other white and yellow 

 butterflies on the banks of rivers, may it not be possible 

 that the appearance of orange stripes or patches would be as 

 injurious to the male as it is useful to the female, by making 

 him a more easy mark for insectivorous birds among his 



