360 THE DESCENT OF MAN. 



in speaking of the difficulty in collecting certain butter- 

 flies in the Malay Archipelago, states that " a dead speci- 

 men pinned upon a conspicuous twig will often arrest an 

 insect of the same species in its headlong flight and bring 

 it down within easy reach of the net, especially if it be of 

 the opposite sex." 



The courtship of butterflies is, as before remarked, a 

 prolonged affair. The males sometimes fight together in 

 rivalry; and many maybe seen pursuing or crowding round 

 the same female. Unless, then, the females prefer one 

 male to another the pairing must be left to mere chance, 

 and this does not appear probable. If, on the other hand, 

 the females habitually, or even occasionally, prefer the 

 more beautiful males, the colors of the latter will have been 

 rendered brighter by degrees, and will have been trans- 

 mitted to both sexes or to one sex, according to the law of 

 inheritance which has prevailed. The process of sexual 

 selection will have been much facilitated, if the conclusion 

 can be trusted, arrived at from various kinds of evidence 

 in the supplement to the ninth chapter; namely, that the 

 males of many Lepidoptera, at least in the imago state, 

 greatly exceed the females in number. 



Some facts, however, are opposed to the belief that female 

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

 been assured by several collectors, fresh females may fre- 

 quently 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 Bom- 

 bycidae, the sexes pair immediately after assuming the 

 imago state; for they cannot feed, owing to the rudiment- 

 ary 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 experi- 

 ence in breeding Bombyx cynthia, is convinced that the 

 females evince no choice or preference. He has kept above 

 three hundred 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 arQ 





