400 NOISES OF INSECTS. 



every sunny bank, cind which make vocal every heath. 

 They begin their song' — which is a short chirp reguhirly 

 interrupted, in Wiiicii it differs from that of the Locusia 

 —long before sun-rise. In the heat of the day it is in- 

 termitted, and resumed in the evening. This sound is 

 tlius produced : — Applying its posterior shank to the 

 thigh, the animal rubs it briskly against the elytrum% 

 doing this alternately \vkh 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 entomo- 

 logist that has noticed this organ. "• On each side of 

 the first segment of the abdomen," says he, " immedi- 

 ately above the origin of the posterior thighs, there i- 

 a considerable and deep aperture of rather an oval 

 form, which is partly closed by an irregular fiat plate 

 or operculum of a hard substance, but covered by a 

 wrinkled flexible membrane. The opening left by 

 this operculum is semi-lunar, 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 intro- 

 duced without resistance. When the pellicle is re- 

 moved, a large cavity appears. In my opinion this 

 aperture, cavity, and above all the membrane in ten- 

 sion, contribute n)uch to produce and augment the 

 sound emitted by the grasshopper^." This descrip- 

 tion, which was taken from the migratory locust (G. mi- 



^ De.Geer,iii,470. "Ibid. 4T1. /. xxiii. /. 2.3. 



