PDF - Wallace Online

v COLOURS OF ANIMALS 373ing in the female may lead to more contrasted markings.Mr. Darwin thinks that here the males have selectedthe more beautiful females ; although one chief fact insupport of his theory of conscious sexual selection is, thatthroughout the whole animal kingdom the males are usuallyso ardent that they will accept any female, while the femalesare coy and choose the handsomest males, whence it isbelieved the general brilliancy of males as compared withfemales has arisen.Perhaps the most curious cases of sexual difference ofcolour are those in which the female is very much more gailycoloured than the male. This occurs most strikingly in somespecies of Pieris in South America, and of Diadema in theMalay islands and in both;cases the females resemble speciesof the uneatable Danaidse and Heliconidse, and thus gain aprotection. In the case of Pieris pyrrha, P. malenka, and P.lorena, the males are plain white and black, while the femalesare orange, yellow, and black, and so banded and spotted asexactly to resemble species of Heliconidae. Mr. Darwinadmits that these bright colours have been acquired forprotection but as there is no; apparent cause for the strictlimitation of the colour to the female, he believes that it hasbeen kept down in the male by its being unattractive to her.This appears to me to be a supposition opposed to the wholetheory of sexual selection itself. For this theory is, thatminute variations of colour in the male are attractive to thefemale, have always been selected, and that thus the brilliantmale colours have been produced. But in this case he thinksthat the female butterfly had a constant aversion to everytrace of colour, even when we must suppose it was constantlyrecurring during the successive variations which resulted insuch a marvellous change in herself. But the case admits ofa much more simple interpretation. For if we consider thefact that the females frequent the forests where the Heliconidseabound, while the males fly much in the open andassemble in great numbers with other white and yellowbutterflies on the banks of rivers, may it not be possiblethat the appearance of orange stripes or patches would be asinjurious to the male as it is useful to the female, by makinghim a more easy mark for insectivorous birds among his