1 2 The Descent of Man 



thought a better instance of sexual selection than the light 

 of the glowworm, exhibited to attract her mate ? Yet the 

 discovery of luminous larvae, which of course have no sexual 

 action, leads Mr. Darwin to observe : ' It is very doubtful 

 whether the primary use of the light is to guide the male to 

 the female ' (vol. i. p. 345). Again, as to certain British field- 

 bugs, he says : ' If in any species the males had differed from 

 the females in an analogous manner, we TYiigJd have been 

 justified in attributing such conspicuous colours to sexual 

 selection with transference to both sexes ' (vol. i. p. 350). As 

 to the stridulating noises of insects (which is assumed to be 

 the result of sexual selection), Mr. Darwin remarks of certain 

 Neuroptera : — ' It is rather surprising that both sexes should 

 have the power of stridulating, as the male is winged and 

 the female wingless ' (vol. i. p. 366) ; and he is again surprised 

 to find that this power is not a sexual character in many 

 Coleoptera (vol. i. p. 382). 



Moths and butterflies, however, are the insects which 

 Mr. Darwin treats of at the greatest length in support of 

 sexual selection. Yet even here he supplies us with posi- 

 tive evidence that in certain cases beauty does not charm the 

 female. He tells us : — 



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

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

 assured by several observers, fresh females may frequently be seen 

 paired with battered, faded, or dingy males.' — Vol. i. p. 400. 



As to the Bombycida3, he adds : — 



' The females 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). Dr. Wallace, who has had 

 such immense experience in breeding Bombyx cynthia, is convinced 

 that the females evince no choice or preference. He has kept above 

 three hundred of these moths living together, and has often found the 

 most vigorous females mated with stunted males.' 



