32 THE SKIN OF INSECTS. 



dience to the law of proportion, it is exceedingly small 

 in crickets, grasshoppers, and locusts. 



The hind back plate, front view ; a, the first piece ; b, the 

 third piece, the second not being: obvious ; c, the fourth piece ; 

 d, d, the under flanks ; e, e, the wing scales of the second pair ; 

 /, /, the breathing spiracles ; g, the cord for pulley. 



In order to render this brief description of the 

 corselet complete, it may be necessary to mention 

 that, on the inner surface of the plates, there are cer- 

 tain remarkable inequalities of surface, and even 

 some distinct parts observable, besides those already 

 described. Amongst these are occasional horny 

 ridges, (*) always formed by the junction of two con- 

 tiguous pieces; and, when they can be detected, they 

 are excellent guides for discovering the boundaries of 

 two pieces, which cannot be distinguished on the out- 

 side. They serve for the attachment of muscles. 

 When these ridges are on the outside, ( 2 ) they often 

 assist in the mechanism of a joint, such as those of 

 the wings. 



Other small pieces are found in the inside of the 

 corselet, sometimes in the form of flat plates raised upon 



(1) In Latin Apodem.ee insertionis. 

 (2) In Latin Apodema articulationis. 



