JIO The Descent of Mail. Part 1L 



others the males are either a little brighter, or very much more 

 superb than the females. The genus Junonia, allied to our 

 Vanessse, offers a nearly parallel case, for although the sexes of 

 most of the species resemble each other, and are destitute of 

 rich colours, yet in certain species, as in J. oenone. the male is 

 rather more bright- coloured than the female, and in a few (for 

 instance J. andremiaja) 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 British 

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

 TheclaB, in which both sexes are nearly alike and wonderfully 

 splendid ; in another species the male is coloured in a similarly 

 gorgeous manner, whilst the whole upper surface of the 

 female is of a dull uniform brown. Our common little English 

 blue butterflies of the genus Lycsena, illustrate the various dif- 

 ferences in colour between the sexes, almost as well, though not 

 in so striking a manner, as the above exotic genera. In Lycxna 

 agestis both sexes have wings of a brown colour, bordered with 

 small ocellated orange spots, and are thus alike. In L. cegou 

 the wings of the male are of a fine blue, bordered with black ; 

 whilst 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 colour 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, and departs more from the 

 usual type of colouring 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 coloured 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 gradation from no difference 

 in colour, 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 colours to the female, or to the male having retained, or 

 perhaps recovered, the primordial colours of the group. It also 

 deserves notice that in those groups in which the sexes differ, 

 the females usually somewhat resemble the males, so that when 



