MUSKJ-MAKTNG INSECTS. 315 



table to illustrate my point. It is not flat, but is bent 

 into little rolls and hollows. 1 put my finger upon one 

 of the elevated parts, and pusli it down, and remove 

 my finger, so. It makes a loud, rattling noise. I re- 

 peat the motion rapidly a number of times, and you 

 hear a succession of these sounds." 



" Certainly they are distinct enough, but they can 

 hardly be called inuskal,'''' remarked the Mistress, 

 laughing, as the loud clatter of the tin sheet resounded 

 through the room. 



" True enough ; but is a kettle-drum any more so ?" 

 queried Aunt Hannah. 



" I am not so much concerned about the testhetical 

 part of my illustration," I replied, "as the practical. 

 Now, Harry, observe, when the drumstick falls upon the 

 tight drum-head, it pushes it down just as my finger did 

 the tin sheet ; when it is lifted the drum-head springs 

 up again, and that motion produces a sound not vuilike 

 that which I have just made. As the skin out of which 

 the drum-head is made is stretched over a hollow cylin- 

 der, or ' barrel,' the vibrations of the air are greatly in- 

 creased, and so also is the intensity of the sound. Do 

 you understand that, Harry?" 



" I think I do, sir," said the boy. 



" Very well ; it is quite in this way that the Cicada's 

 note is produced. These convex membi'anes or drums 

 of which I spoke are the drum-heads. But where 

 are the 'barrels' over which they are stretched? 

 Here they are. There are certain cavities within the 

 body of the insect which may be seen on raising two 



