100 EVENINGS AT THE MICKOSCOPE. 



dcrable and deep aperture of rather an oval form, 

 wliicli is partly closed by an irregular flat plate or op- 

 erculum of a hard substance, but covered by a wrinkled 

 flexible membrane. The opening left by this opercu- 

 him is semilunar, and at the bottom of the cavity is a 

 tvliite 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 cav- 

 ity appears. In my oj)inion this aperture, cavity, and 

 above all the membrane in tension, contribute much to 

 produce and augment the sound emitted by the grass- 

 hopper." * 



In this case we may without hesitation conclude 

 that the friction of the thigh-plates and shank-points 

 on the rough edges of the wing-cases, produces the 

 musical vibration of the tense membrane, as rubbing 

 a wet fflass with the finger will vield a loud musical 

 note. 



The most elaboi-ate contrivance for the production 

 of sounds among the Insect races, however, is found 

 among the Cicadas, celebrated in classical poetry as the 

 very impersonations of song and eloquence. I regret 

 I cannot show you this apparatus ; for though we have 

 a British species, — lately discovered in the New Forest, 

 — it is very rare. Should you travel, however, either 

 in the old or new world, you will have abundant op- 

 portunities of using your microscope to verify the fol- 

 lowing description by our prince of entomologists, IMr. 

 Kirby. 



" If you look at the under side of tlie body of a 



* De Geer, iii. 471. 



