3 1 8 The Descent of Man. Part II. 



butterflies prefer the more beautiful males; thus, as I have 

 been assured by several collectors, fresh females may frequently 

 be seen paired with battered, faded, or dingy males ; but this is 

 a circumstance which could hardly fail often to follow from the 

 males emerging from their cocoons earlier than the females. 

 With moths of the family of the Bombycidse, the sexes pair 

 immediately after assuming the imago state; for they cannot 

 feed, owing to the rudimentary condition of their mouths. The 

 females, as several entomologists have remarked to me, lie in an 

 almost torpid state, and appear not to evince the least choice in 

 regard to their partners. This is the case with the common 

 silk-moth (B. mori), as I have been told by some continental 

 and English breeders. Dr. Wallace, who has had great 

 experience in breeding Bvrnbyx cynthia, is convinced that the 

 females evince no choice or preference. He has kept above 

 300 of these moths together, and has often found the 

 most vigorous females mated with stunted males. The reverse 

 appears to occur seldom ; for, as he believes, the more vigorous 

 males pass over the weakly females, and are attracted by those 

 endowed with most vitality. Nevertheless, the Bonibycidae, 

 though obscurely-coloured, are often beautiful to our eyes from 

 their elegant and mottled shades. 



I have as yet only referred to the species in which the males 

 are brighter coloured than the females, and I have attributed 

 their beauty to the females for many generations having chosen 

 and paired with the more attractive males. But converse 

 cases occur, though rarely, in which the females are more 

 brilliant than the males ; and here, as I believe, the males have 

 selected the more beautiful females, and have thus slowly added 

 to their beauty. We do not know why in various classes of 

 animals the males of some few species have selected the more 

 beautiful females instead of having gladly accepted any female, 

 as seems to be the general rule in the animal kingdom ; but if, 

 contrary to what generally occurs with the Lepidoptera, the 

 females were much more numerous than the males, the latter 

 would be likely to pick out the more beautiful females. Mr. 

 Butler shewed me several species of Callidryas in the British 

 Museum, in some of which the females equalled, and in others 

 greatly surpassed the males in beauty; for the females alone 

 have the borders of their wings suffused with crimson and 

 orange, and spotted with black. The plainer males of these 

 species closely resemble each other, showing that here the 

 females have been modified ; whereas in those cases, where the 

 males are the more ornate, it is these which have been modified, 

 the females remaining closely alike. 



