. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. Chap. X.] ORTHOPTERA. 343 ; ^® Dr. Scudder was able to excite one of these in- sects to answer him, by rubbing on a file with a quill.^" In both sexes a remarkable auditory apparatus has been discovered by,Von Siebold, situated in the front legs.^^ In the three Families the sounds are differently pro- duced. In the males of the Achetidoe both wing-covers have the same structure; and this in the field-cricket {Gryllus
. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. Chap. X.] ORTHOPTERA. 343 ; ^® Dr. Scudder was able to excite one of these in- sects to answer him, by rubbing on a file with a quill.^" In both sexes a remarkable auditory apparatus has been discovered by,Von Siebold, situated in the front legs.^^ In the three Families the sounds are differently pro- duced. In the males of the Achetidoe both wing-covers have the same structure; and this in the field-cricket {Gryllus canipestrls^ fig. 10) consists, as described by Landois,^'' of from 131 to 138 sharp, transverse ridges or teeth {st) on 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 opposite 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 have here given a drawing (iig. 11) of the teeth on the under side of the p-j^ -^-^^ —Teeth of nervure of another species of Gryllus, viz., ^Sfcus^ffm G. domestictlS. Landois). In the Locustidee the opposite wing-covers differ in structure (fig. 12), and cannot, as in the last family, be in- differently used in a reversed manner. The left wing, which acts as the bow of the fiddle, lies over the right ^^ 'The Naturalist on the Amazons,' vol. i. 1863, p 252. Mr. Bates gives a very interesting discussion on the gradations in the musical appa- ratus of the three families. See also Westwood, * Modem Class.' vol. ii. pp. 445, 453. 30 ' Proc. Boston Soc. of Nat. Hist.' vol. xi. April, 1868. 3' 'Nouveau Manuel d'Anat. Comp.' (French translat.), torn. i. 1850, p. set. 8' 'Zeitschrift fiir wissenschaft. Zoolog.' B. xvii. 1867, s.
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