sexval selection 415 



Bombycidse the sexes pair immediatelj after assuming tlie 

 imago state; for they cannot feed, owing to the rudimentary 

 condition of their mouths. The females, as several ento- 

 mologists 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 

 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 vigor- 

 ous males pass over the weakly females, and are attracted 

 by those endowed with most vitality. Nevertheless, the 

 Bombycidse, though obscurely colored, 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 colored 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. "Wa 

 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. But- 

 ler showed me several species of Oallidryas in the British 

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

 others greatly surpassed, the males in beauty; for tho 

 females alone have the borders of their wings suffused 

 with crimson and orange, and spotted with black. The 



