. 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. S23 TBB DESCENT OF MAlv. from 131 to 138 sharp, transverse ridges or teeth {st) oi| the under side of one of the nervures of the wing-cover. This toothed nervure is rapidly scraped across a projecting, smooth, hard nervure (r) on the upper surface of the oppo- site wing. First one wing is rubbed over the other, and then the movement is reversed. Both wings are raised a little at the same time, so as to increase
. 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. S23 TBB DESCENT OF MAlv. from 131 to 138 sharp, transverse ridges or teeth {st) oi| the under side of one of the nervures of the wing-cover. This toothed nervure is rapidly scraped across a projecting, smooth, hard nervure (r) on the upper surface of the oppo- site wing. First one wing is rubbed over the other, and then the movement is reversed. Both wings are raised a little at the same time, so as to increase the resonance. In some species the wing-covers of the males are furnished at the base with a talc-like plate.* I here give a drawing (fig. 12) of the teeth on the under side of the nervure of another species of Gryllus, viz., G, domesticus. With respect to the formation of these teeth. Dr. Gruber has shown f that they have been developed by the aid of selection, from the minute scales and hairs with which the wings and body are covered, and I came to the same conclusion with respect to those of the Coleoptera. But Dr. Gruber further shows that their development is in part directly due to the stimulus from, the friction of one wing over the other. In the Locustidse the opposite wing-covers differ from each other in structure (fig 13), ^NerviirJof Gryi^ ^^^ ^^^^ actiou cannot, as in the last family, 1 u s domesticus be reversed The left wing, which acts as the (from Landois). ^^^^^ j-^^ ^^^^ ^^^ right wing which scrves as the fiddle. One of the nervures {a) on the under surfai?^ of the former is finely serrated, and is scraped acros! he prominent nervures on the upper surface of the opposite or right wing. In our British Fhasgonura viridissima it appeared to me that the serrated nervure is rubbed against the rounded hind-corner of the opposite wing, the edge of which is thickened, colored brown, and very sharp \n the right wing, but not in the left, there is a little plate, as tr
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthumanbeings, bookyear
