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Show 351 SEXUAL SELECTION. PART II. scribed by Landois,32 of from 131 to 138 sharp, transverse ridges or teeth ( st) on the under side of one of tb.e nervures of the wing-cover. This toothed nervure 1s rapidly scraped across a projecting, smoo~b, h~rd nerv~ue (r) on the upper surface of the opposite wmg. Fust 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 wingcovers of the males are furnished at the base with a talc-like plate.33 I baYe here given a drawing (fig. 11) Fig.n. Teeth ofNervme of the teeth on the under side of the of Gryllus domesticus nervnre of another species of Gry1lus, (from LamloiB). viz. G. domesticus. In the Locustidro the opposite wing-covers differ in structure (fig. 1~), and cannot, as in the last family, be indifferently used in a reversed manner. The left winO' which acts as the bow of the fiddle, lies over the O' right wing which serves as the fiddle itself. One ?f the nervures (a) on the under surface of the former 1s finely serrated, and is scraped across the prominent nervures on the upper surface of the opposite or right wing. In our British Phasgonura viridissirna 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, coloured brown, and very sharp. In the right wing, but not in the left, there is a little plate, as transparent as talc, surrounded by nervures, and called the speculum. In Ephippiger vitium, a member of this same family, we have a curious :n 'Zeitschrift fiir wissenschaft. Zoolog.' B. xvii. 1867, s. 117. a3 Westwood, 'Modern Class. of Insects,' vol. i. p. 440. C: rAP. :X. ORTHOPTERA. 355 subordinate modification; for the wing-covers are greatly reduced in size, but "the posterior part of the pro-thorax " is elevated into a kind of dome over the wing-covers, " and which bas probably the effect of increasing the " sound." 34 Fig. 12. Chlorocrelus Tanana (from Bates). a. b. T,obes of opposite wing-covers. We thus see that the musical apparatus is more differentiated or specialised in the Locustidre, which includes I believe the most powerful performers in the Order, than in the Achetidre, in which both wingcovers have the same structure and the same function.35 Lanclois, however, detected in one of the Locustidre, nmnely in Decticus, a short and narrow row of small :II Westwood,' 1\iodern Class. of Insects,' vol. i. p. 453. J;; Lauclois, ibid. s. 121, 122. 2 A 2 |
