The Descent of Man

duced by the vibration of the lips of the spiracles,
which are set into motion by a current of
air emitted from the tracheae; but this view has
lately been disputed. Dr. Powell appears to
have proved (25. 'Transactions of the New Zealand
Institute,' vol. v. 1873, p. 286.) that it is
produced by the vibration of a membrane, set
into action by a special muscle. In the living
insect, whilst stridulating, this membrane can
be seen to vibrate; and in the dead insect the
proper sound is heard, if the muscle, when a
little dried and hardened, is pulled with the
point of a pin. In the female the whole complex
musical apparatus is present, but is much less
developed than in the male, and is never used
for producing sound.
With respect to the object of the music, Dr.
Hartman, in speaking of the Cicada septemdecim
of the United States, says (26. I am indebted
to Mr. Walsh for having sent me this extract
from 'A Journal of the Doings of Cicada sep-