INSECTS: WINGS AND THEIR APPENDAGES 107 



The Locusts and Grasshoppers, however, do, it appears, 

 make use of their hind legs in producing their crink. If 

 you look at this Grasshopper's leg, you will see that the 

 thigh is marked with a number of transverse overlapping 

 angular plates, and that the shank carries a series of short 

 horny points along each side. The insect when it crinks 

 brings the shank up to its thigh, and rubs both to and fro 

 against the wing-sheaths, doing this by turns with the right 

 and left legs, which causes the regular breaks in the sound. 

 The drum, on which this rubbing vibrates, has been de- 

 scribed by the anatomist, De Geer: "On each side of the 

 first segment of the abdomen," says he, "immediately 

 above the origin of the posterior thighs, there is a con- 

 siderable and deep aperture of rather an oval form, which 

 is partly closed by an irregular flat plate or operculum of 

 a hard substance, but covered by a wrinkled flexible mem- 

 brane. The opening left by this operculum is semilunar, 

 and at the bottom of the cavity is a white pellicle of con- 

 siderable tension, and shining like a little mirror. On 

 that side of the aperture which is toward the head there 

 is a little oval hole, into which the point of a pin may be 

 introduced without resistance. When the pellicle is re- 

 moved, a large cavity appears. In my opinion this aper- 

 ture, cavity, and above all the membrane in tension, con- 

 tribute much to produce and augment the sound emitted 

 by the grasshopper. ' ' l 



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 vibra- 

 tion of the tense membrane, as rubbing a wet glass with 

 the finger will yield a loud musical note. 



1 De Geer, iii. 471. 



