NOISES OF INSECTS. 



323 



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 commonly 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 Acridce — long before sun- 

 rise. 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 Tetti- 

 gonias, they have also a tympanum or drum. De Geer, who 

 examined the insects he describes with the eye of an anato- 

 mist, seems to be the only entomologist that has noticed this 

 organ. " On each side of the first segment of the abdomen," 

 says he, es 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 in- 

 troduced 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 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 



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

 supra, 929. 



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



Y 2 



