NOISES OF INSECTS. 405 
digious sounds. I have lately mentioned ‘to you the 
drum of certain grasshoppers; this, however, appears 
to be an organ of a very simple structure; but since it 
is essential to the economy of the Cicade that their 
males should so much exceed all other insects in the 
loudness of their tones, they are furnished with a much 
more complex, and indeed most wonderful, apparatus, 
which I shall now describe. If you look at the under- 
side of the body of a male, the first thing that will strike 
you is a pair of large plates of an irregular form—in some 
semi-oval, in others triangular, in others again a seg- 
ment of a circle of greater or less diameter—covering 
the anterior part of the belly, and fixed to the trunk be- 
tween the abdomen and the hind legs*. ‘These are the 
drum-covers or opercula, from beneath which the sound 
issues. At the base of the posterior legs, just above 
each operculum, there is a small pointed triangular pro- 
cess (pessellum)>, the object of which, as Reaumur sup- 
poses, is to prevent them from being too much elevated. 
When an operculum is removed, beneath it you will 
find on the exterior side a hollow eavity, with a mouth 
somewhat linear, which seems to open into the interior 
of the abdomen‘: next to this, on the inner side, is 
another large cavity of an irregular shape, the bottom 
of which is divided into three portions; of these the 
posterior is lined obliquely with a beautiful membrane, 
which is very tense—in some species semi-opake, and in 
others transparent—and reflects all the colours of the 
rainbow. This mirror is not the real organ of sound, 
a Prate VIII. Fic. 1.8.aa. Reaum. v. ¢. xvi. f 9. uu, 
> Pare VIII. Fic. 18. bb. Reaum. wdi supra, t. xvi. f. 11. 6. 
¢ Reaum. ibid. f. 3. 22. 
