pursuing the same female, we can hardly believe that the pairing is
left to blind chance that the female exerts no choice, and is not
influenced by the gorgeous colours or other ornaments with which the
male is decorated.
If we admit that the females of the Homoptera and Orthoptera appreciate
the musical tones of their male partners, and that the various
instruments have been perfected through sexual selection, there is
little improbability in the females of other insects appreciating
beauty in form or colour, and consequently in such characters having
been thus gained by the males. But from the circumstance of colour
being so variable, and from its having been so often modified for the
sake of protection, it is difficult to decide in how large a proportion
of cases sexual selection has played a part. This is more especially
difficult in those Orders, such as Orthoptera, Hymenoptera, and
Coleoptera, in which the two sexes rarely differ much in colour; for we
are then left to mere analogy. With the Coleoptera, however, as before
remarked, it is in the great Lamellicorn group, placed by some authors
at the head of the Order, and in which we sometimes see a mutual
attachment between the sexes, that we find the males of some species
possessing weapons for sexual strife, others furnished with wonderful
horns, many with stridulating organs, and others ornamented with
splendid metallic tints. Hence it seems probable that all these
characters have been gained through the same means, namely sexual
selection. With butterflies we have the best evidence, as the males
sometimes take pains to display their beautiful colours; and we cannot
believe that they would act thus, unless the display was of use to them
in their courtship.
When we treat of Birds, we shall see that they present in their
secondary sexual characters the closest analogy with insects. Thus,
many male birds are highly pugnacious, and some are furnished with
special weapons for fighting with their rivals. They possess organs
which are used during the breeding-season for producing vocal and
instrumental music. They are frequently ornamented with combs, horns,
wattles and plumes of the most diversified kinds, and are decorated
with beautiful colours, all evidently for the sake of display. We shall
find that, as with insects, both sexes in certain groups are equally
beautiful, and are equally provided with ornaments which are usually
confined to the male sex. In other groups both sexes are equally
360