Order, Orthoptera.—The males in the three saltatorial families belonging to this Order are remarkable for their musical powers, namely the Achetidæ or crickets, the Locustidæ for which there is no exact equivalent name in English, and the Acridiidæ or grasshoppers. The stridulation produced by some of the Locustidæ is so loud that it can be heard during the night at the distance of a mile;[451] and that made by certain species is not unmusical even to the human ear, so that the Indians on the Amazons keep them in wicker cages. All observers agree that the sounds serve either to call or excite the mute females. But it has been noticed[452] that the male migratory locust of Russia (one of the Acridiidæ) whilst coupled with the female, stridulates from anger or jealousy when approached by another male. The house-cricket when surprised at night uses its voice to warn its fellows.[453] In North America the Katy-did (Platyphyllum concavum, one of the Locustidæ) is described[454] as mounting on the upper branches of a tree, and in the evening beginning “his noisy babble, while rival notes issue from the neighbouring trees, and the groves resound with the call of Katy-did-she-did, the live-long night.” Mr. Bates, in speaking of the European field-cricket (one of the Achetidæ), says, “the male has been observed to place itself in the evening at the entrance of its burrow, and stridulate until a female approaches, when the louder notes are succeeded by a more subdued tone, whilst the successful musician caresses with his antennæ
Fig. 10. Gryllus campestris (from Landois).
Right-hand figure, under side of part of the wing-nervure, much magnified, showing the teeth, st.
Left-hand figure, upper surface of wing-cover, with the projecting, smooth nervure, r., across which the teeth (st) are scraped. the mate he has won.”[455] Dr. Scudder was able to excite one of these insects to answer him, by rubbing on a file with a quill.[456] In both sexes a remarkable auditory apparatus has been discovered by Von Siebold, situated in the front legs.[457]
In the three Families the sounds are differently produced. In the males Of the Achetidæ both wing-covers have the same structure; and this in the field-cricket (Gryllus campestris, fig. 10) consists, as described by Landois,[458] 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
Fig. 11. Teeth of Nervure of Gryllus domesticus (from Landois). 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.[459] I have here given a drawing (fig. 11) of the teeth on the under side of the nervure of another species of Gryllus, viz. G. domesticus.
In the Locustidæ the opposite wing-covers differ in structure (fig. 12), and cannot, as in the last family, be indifferently used in a reversed manner. The left wing, which acts as the bow of the fiddle, lies over the right wing which serves as the fiddle itself. One of the nervures (a) on the under surface of the former is finely serrated, and is scraped across the prominent nervures on the upper surface of the opposite or right wing. In our British Phasgonura 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, 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 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 has probably the effect of increasing the sound.”[460]
Fig. 12. Chlorocœlus Tanana (from Bates), a, b. Lobes of opposite wing-covers.