Chap. XL BUTTERFLIES AND MOTHS. 401 



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 Bombyeiclaa, the sexes pair imme- 

 diately 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 such immense 

 experience in breeding Bomhtjx cynthia, is convinced 

 that the females evince no choice or preference. He 

 has kept above 300 of these moths living together, and 

 has often found the most vigorous females mated with 

 stunted males. The reverse apparently seldom occurs ; 

 for, as he believes, the more vigorous males pass over the 

 weakly females, being attracted by those endowed with 

 most vitality. Although we have been indirectly in- 

 duced to believe that the females of many species prefer 

 the more beautiful males, I have no reason to suspect, 

 either with moths or butterflies, that the males are 

 attracted by the beauty of the females. If the more 

 beautiful females had been continually preferred, it is 

 almost certain, from the colours of butterflies being so 

 frequently transmitted to one sex alone, that the females 

 would often have been rendered more beautiful than 

 their male partners. But this does not occur except in 

 a few instances ; and these can be explained, as we 

 shall presently see, on the principle of mimickry and 

 protection. 



As sexual selection primarily depends on variability, 

 a few words must be added on this subject. In respect 

 vol. i. 2d 



