The Descent of Man

een rendered larger and stronger than the
females. On the contrary, they are usually smaller,
so that they may be developed within a
shorter time, to be ready in large numbers for
the emergence of the females.
In two families of the Homoptera and in three
of the Orthoptera, the males alone possess
sound-producing organs in an efficient state.
These are used incessantly during the breedingseason,
not only for calling the females, but
apparently for charming or exciting them in
rivalry with other males. No one who admits
the agency of selection of any kind, will, after
reading the above discussion, dispute that these
musical instruments have been acquired
through sexual selection. In four other Orders
the members of one sex, or more commonly of
both sexes, are provided with organs for producing
various sounds, which apparently serve
merely as call-notes. When both sexes are thus
provided, the individuals which were able to