SEXUAL SELECTION 405 



dremiaja) the male is so different from the female that 

 he might be mistaken for an entirely distinct species. 



Another striking case was pointed out to me in the Brit- 

 ish Museum by Mr. A. Butler, namely, one of the tropical 

 American Theclse, in which both sexes are nearly alike and 

 wonderfully splendid; in another species the male is colored 

 in a similarly gorgeous manner, while the whole upper sur- 

 face of the female is of a dull uniform brown. Our common 

 little English blue butterflies of the genus Lycsena illustrate 

 the various differences in color between the sexes almost as 

 well, though not in so striking a manner, as the above exotic 

 genera. In Lycaena agestis both sexes have wings of a brown 

 color, bordered with small ocellated orange spots, and are 

 thus alike. In L. mgon the wings of the male are of a fine 

 blue, bordered with black; while those of the female are 

 brown, with a similar border, closely resembling the wings 

 of L. agestis. Lastly, in L. avion both sexes are of a blue 

 color and are very like, though in the female the edges of 

 the wings are rather duskier, with the black spots plainer; 

 and in a bright blue Indian species both sexes are still more 

 alike. 



I have given the foregoing details in order to show, in 

 the first place, that when the sexes of butterflies differ the 

 male, as a general rule, is the more beautiful, aad departs 

 more from the usual type of coloring of the group to which 

 the species belongs. Hence in most groups the females of 

 the several species resemble each other much more closely 

 than do the males. In some cases, however, to which I shall 

 hereafter allude, the females are colored more splendidly 

 than the males. In the second place, these details have 

 been given to bring clearly before the mind that, within 

 the same genus, the two sexes frequently present every gra- 

 dation from no difference in color to so great a difference 

 that it was long before the two were placed by entomologists 

 in the same genus. In the third place, we have seen that 

 when the sexes nearly resemble each other, this appears due 

 either to the male having transferred his colors to the fe- 



