greater number the males are decorated with beautiful metallic tints in
a diversified manner, and differ much from their females. The females
throughout the genus retain the same general style of colouring, so
that they resemble one another much more closely than they resemble
their own males.
In the genus Papilio, all the species of the Aeneas group are
remarkable for their conspicuous and strongly contrasted colours, and
they illustrate the frequent tendency to gradation in the amount of
difference between the sexes. In a few species, for instance in P.
ascanius, the males and females are alike; in others the males are
either a little brighter, or very much more superb than the females.
The genus Junonia, allied to our Vanessae, 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 Theclae, 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 Lycaena, illustrate
the various differences in colour 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 colour, bordered with
small ocellated orange spots, and are thus alike. In L. oegon the wings
of the males 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. arion 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 shew, 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
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