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The Descent of Man

The Descent of Man

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one <strong>of</strong> the nervures <strong>of</strong> the wing-cover. This<br />

toothed nervure is rapidly scraped across a<br />

projecting, smooth, hard nervure (r) on the upper<br />

surface <strong>of</strong> the opposite wing. First one wing<br />

is rubbed over the other, and then the movement<br />

is reversed. Both wings are raised a little<br />

at the same time, so as to increase the resonance.<br />

In some species the wing-covers <strong>of</strong> the males<br />

are furnished at the base with a talc-like<br />

plate. (35. Westwood, 'Modern Classification <strong>of</strong><br />

Insects,' vol. i. p. 440.) I here give a drawing<br />

(Fig. 12) <strong>of</strong> the teeth on the under side <strong>of</strong> the<br />

nervure <strong>of</strong> another species <strong>of</strong> Gryllus, viz., G.<br />

domesticus. With respect to the formation <strong>of</strong><br />

these teeth, Dr. Gruber has shewn (36. 'Ueber<br />

der Tonapparat der Locustiden, ein Beitrag<br />

zum Darwinismus,' 'Zeitschrift fur wissenschaft.<br />

Zoolog.' B. xxii. 1872, p. 100.) that they<br />

have been developed by the aid <strong>of</strong> selection,<br />

from the minute scales and hairs with which<br />

the wings and body are covered, and I came to<br />

the same conclusion with respect to those <strong>of</strong> the

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