The Descent of Man

grating sound, as is now the case with the
wing-covers of the females. (39. Mr. Walsh also
informs me that he has noticed that the female
of the Platyphyllum concavum, "when captured
makes a feeble grating noise by shuffling
her wing-covers together.") A grating sound
thus occasionally and accidentally made by the
males, if it served them ever so little as a lovecall
to the females, might readily have been
intensified through sexual selection, by variations
in the roughness of the nervures having
been continually preserved.
[Fig.14. Hind-leg of Stenobothrus pratorum: r,
the stridulating ridge; lower figure, the teeth
forming the ridge, much magnified (from Landois).
Fig.15. Pneumora (from specimens in the British
Museum). Upper figure, male; lower figure,
female.]