100 EVENINGS AT THE MICEOSCOPE. 



derable and deep aperture of rather an oval form, 

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

 erculum of a bard "Substance, but covered by a wrinkled 

 flexible membrane. The opening left by this opercu- 

 lum is semihmar, 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 cav- 

 ity 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 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 glass with the finger will yield a loud musical 

 note. 



The most elaborate contrivance for the production 

 of sounds among the Insect races, however, is found 

 among the Cicadse, 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 verj'' 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, Mr. 

 Kirby. 



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



* De Geer, iii. 4Y1. 



