in a furrow designed to receive it, and then draws the leg briskly up
and down. He does not play both fiddles together, but alternately,
first upon one and then on the other. In many species, the base of the
abdomen is hollowed out into a great cavity which is believed to act as
a resounding board. In Pneumora (Fig. 15), a S. African genus belonging
to the same family, we meet with a new and remarkable modification; in
the males a small notched ridge projects obliquely from each side of
the abdomen, against which the hind femora are rubbed. (42. Westwood,
Modern Classification, vol i. p. 462.) As the male is furnished with
wings (the female being wingless), it is remarkable that the thighs are
not rubbed in the usual manner against the wing-covers; but this may
perhaps be accounted for by the unusually small size of the hind-legs.
I have not been able to examine the inner surface of the thighs, which,
judging from analogy, would be finely serrated. The species of Pneumora
have been more profoundly modified for the sake of stridulation than
any other orthopterous insect; for in the male the whole body has been
converted into a musical instrument, being distended with air, like a
great pellucid bladder, so as to increase the resonance. Mr. Trimen
informs me that at the Cape of Good Hope these insects make a wonderful
noise during the night.
In the three foregoing families, the females are almost always
destitute of an efficient musical apparatus. But there are a few
exceptions to this rule, for Dr. Gruber has shewn that both sexes of
Ephippiger vitium are thus provided; though the organs differ in the
male and female to a certain extent. Hence we cannot suppose that they
have been transferred from the male to the female, as appears to have
been the case with the secondary sexual characters of many other
animals. They must have been independently developed in the two sexes,
which no doubt mutually call to each other during the season of love.
In most other Locustidae (but not according to Landois in Decticus) the
females have rudiments of the stridulatory organs proper to the male;
from whom it is probable that these have been transferred. Landois also
found such rudiments on the under surface of the wing-covers of the
female Achetidae, and on the femora of the female Acridiidae. In the
Homoptera, also, the females have the proper musical apparatus in a
functionless state; and we shall hereafter meet in other divisions of
the animal kingdom with many instances of structures proper to the male
being present in a rudimentary condition in the female.
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