390 
SEXUAL SELECTION. 
Part II. 
are nearly alike and wonderfully splendid ; in another, 
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 butter- 
flies of the genus Lycsena, illustrate the various differ- 
ences in colour between the sexes, almost as well, 
though not in so striking a manner, as the above exotic 
genera. In Lgcsena agestis both sexes have wings of a 
brown colour, bordered with small ocellated orange 
spots, and are consequently alike. In L . oegon the 
wings of the male are of a fine blue, bordered with 
black ; whilst the wings of the female are brown, with 
a similar border, and closely resemble those of L. agestis. 
Lastly, in L. avion both sexes are of a blue colour and 
nearly alike, though in the female the erlges of the 
wings are rather duskier, with the black spots plainer; 
and in a bright blue Indian species both sexes are still 
more closely alike. 
I have given the foregoing cases in some detail in 
order to shew, in the first place, that when the sexes of 
butterflies differ, the male as a general rule is the most 
beautiful, and departs most from the usual type of colour- 
ing 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 exceptional cases, however, to which I shall here- 
after allude, the females are coloured more splendidly 
than the males. In the second place these cases 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 dif- 
ference 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 apparently may be due either to the 
