The Descent of Man

me number of females; in order, therefore, to
discover whether the sexes differed in their
power of stridulating, my son, Mr. F. Darwin,
collected fifty-seven living specimens, which he
separated into two lots, according as they made
a greater or lesser noise, when held in the same
manner. He then examined all these specimens,
and found that the males were very nearly in
the same proportion to the females in both the
lots. Mr. F. Smith has kept alive numerous specimens
of Monoynchus pseudacori (Curculionidae),
and is convinced that both sexes stridulate,
and apparently in an equal degree.
Nevertheless, the power of stridulating is certainly
a sexual character in some few Coleoptera.
Mr. Crotch discovered that the males alone
of two species of Heliopathes (Tenebrionidae)
possess stridulating organs. I examined five
males of H. gibbus, and in all these there was a
well- developed rasp, partially divided into
two, on the dorsal surface of the terminal ab-