NOISES OF INSECTS. 533 



arranged, 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 speci- 

 mens, 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.^ 



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 Acrida. — 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^, 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 

 describes 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 

 abdomen," 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 towards 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."^ This 

 description, which was taken from the migratory locust (L. migratoria) , 

 answers tolerably 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 sub- 

 stance of the segment. This apparatus so much resembles the drum of 

 the Cicadce, 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.* 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.^ 



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 Cica- 



> Burmeister, Manual of Enlom. 470. Goureau, ubi supra. Newport, ubi supra, 929. 

 « De Geer, iii. 470. 3 Hjjd. 471. t. xxiii. f. 2, 3. 



4 Goureau {op. cit ) anrl Mailer (Burmeister, Manual, 572.) regard this drum as an audi- 

 tory organ, but probably without sufBcient grounds. 

 * Osbeck's Voy. i. 71. 



45* 



