498 NOISES OF INSECTS. 



produces similar sounds. A still farther proof that these notched nervures 

 or files are the main agents in producing the sounds, is afforded by the 

 facts that their notches are more distinct in newly disclosed specimens, 

 especially of Acrida viridissima, than in older individuals, in which they 

 have been partially obliterated by use ; and that the sounds, as M. 

 Goureau has remarked, may be readily produced in the dead insect by 

 gently rubbing the bases of the elytra together, which could not happen if 

 the rushing of the air from the spiracles had any effect in producing 

 them. 1 



The last description of singers that I shall notice amongst the Locustina, 

 and which includes the migratory locust, are those that are more com- 

 monly denominated grasshoppers. To this genus belong the little chirpers 

 that we hear in every sunny bank, and which make vocal every heath. 

 They begin their song which is a short chirp regularly interrupted, in 

 which it differs from that of the Acridcs long before sunrise. In the heat 

 of the day it is intermitted, and resumed in the evening. This sound is 

 thus produced : Applying its posterior shank to the thigh, the animal 

 rubs it briskly against the elytrum 2 , doing this alternately with the right 

 and left legs, which causes the regular breaks in the sound. But this is 

 not their whole apparatus of song since, like the Tettigoniae, they have 

 also a tympanum or drum. De Geer, who examined the insects he de- 

 scribes with the eye of an anatomist, seems to be the only entomologist that 

 has noticed this organ. " On each side of the first segment of the ab- 

 domen," says he, " immediately above the origin of the posterior thighs, 

 there is a considerable and deep aperture of rather an oval form, which is 

 partly closed by an irregular flat plate or operculum of a hard substance, 

 but covered by a wrinkled flexible membrane. The opening left by this 

 operculum is semilunar, and at the bottom of the cavity is a white pellicle 

 of considerable tension, and shining like a little mirror. On that side of 

 the aperture which is towands the head there is a little oval hole, into 

 which the point of a pin may be introduced without resistance. When 

 the pellicle is removed, a large cavity appears. In my opinion this aperture, 

 cavity, and above all the membrane in tension, contribute much to produce 

 and augment the sound emitted by the grasshopper." 3 This description, 

 which was taken from the migratory locust (L. migratoria), answers tole- 

 rably well to the tympanum of our common grasshoppers; only in them 

 the aperture seems to be rather semicircular, and the wrinkled plate 

 which has no marginal hairs is clearly a continuation of the substance of 

 the segment. This apparatus so much resembles the drum of the Cicada?, 

 that there can be little doubt as to its use. The vibrations caused by the 

 friction of the thighs and elytra striking upon this drum are reverberated 

 by it, and so intenseness is given to the sound. 4 In Spain, we are told 

 that people of fashion keep these animals called there Grillo in cages, 

 which they name Grilleria, for the sake of their song. 5 



I shall conclude this diatribe upon the noises of insects with a tribe that 

 have long been celebrated for their musical powers : I mean the Cicadiadte, 



1 Burmeister, Manual of Entom. 470. Goureau, ubi supra. Newport, ubi supra, 

 929. 



2 De Geer, iii. 470. 5 Ibid. 471. t. xxiii. f. 2, 3. 



4 Goureau (op. cit.) and Miiller (Burmeister, Manual, 572.) regard this drum as an 

 auditory organ, but probably without sufficient grounds. 



5 Osbeck's Voy. i. 71. 



