. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings; Sexual selection in animals; Sexual dimorphism (Animals); Sex differences. 334 THE DESCENT OF MAN. covers had serrated nervures on the under surface and couW be indifEerently used as the bow; but that in the Locustida© the two wing-covers gradually became differentiated and perfected on the principle of the division of labor, the one to act exclusively as the bow and the other as the fiddle. Dr. Grubei akes the same view, and has shown that rudi- mentary teeth are commonly found on the
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings; Sexual selection in animals; Sexual dimorphism (Animals); Sex differences. 334 THE DESCENT OF MAN. covers had serrated nervures on the under surface and couW be indifEerently used as the bow; but that in the Locustida© the two wing-covers gradually became differentiated and perfected on the principle of the division of labor, the one to act exclusively as the bow and the other as the fiddle. Dr. Grubei akes the same view, and has shown that rudi- mentary teeth are commonly found on the inferior surface of the right wing. By what steps the more simple appa- ratus in the Achetidae originated we do not know, but it is probable that the basal portions of the wing-covers origi- nally overlapped each 9ther as they do at present; and that the friction of the nervures produced a grating sound as is now the case with the wing- covers of the females.* A grating sound thus occasion^ ally and accidentally made by the males,if it served them ever so little as a love-call to the fe- males, might readily have been intensified through sexual se- lection by variations in the roughness of the nervures hav- ing been continuallypreserved. Fig. 14, Hind-ieg of stenobothrus pra- ^^ ^^c last and third family, torum. i\ the stridulating rid^e; namelv, the AcridlldaB Or [^lfm'u"o1f-^a%^arXX"nlo^^^^ grasshoppers, the stridulation is produced in a very differ- ent manner, and according to Dr. Scudder, is not so shrill as in the preceding families. The inner surface of the femur (fig. 14, r) is furnished with a longitudinal row of minute, elegant, lancet-shaped, elastic teeth from eighty- five to ninety-three in number;f and these are scraped across the sharp, projecting nervures on the wing-covers which are thus made to vibrate and resound. HarrisJ says that when one of the males begins to play he first '' bends the shank of the hind-leg beneath the thigh, where it is *Mr.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthumanbeings, bookyear
