96 



FIRST LMSOm IN ZOOLOGY. 



the under side of the uppermost of the fore-wings a sort of 

 file which rubs over a resonant surface, like a drum's head. 

 The file may be likened to the bow, and the drum-like 

 space to the body of the violin. Thus, most grasshoppers 

 are fiddlers, and during the summer, both by day and night, 

 the air resounds with the music of these primitive violin- 

 ists. This noise may add to our pleasure or become tedi- 

 ous and disagreeable. This makes little difEerence, for in- 

 sect music is all-important. It is the cricket's love-call, 

 A B 



Fig. 102. — A^ thoracic stigma of the house-fly: Sb^ valve which closes the open- 

 ing. B, C, diagrammatic figures of the internal apparatus which clost-s the 

 trachea, in the stag beetle: B, the trachea open ; in C. closed; .st, the si igma, 

 with its grated lips; C<, cuticula of the body-walls; F/c, closing-pouch; Vbii, 

 closing-bow; Vba, closing-band; M, occlusor muscle.— From Judeich and 

 Nitsche, after Landois. 



and were crickets, etc., deaf and dumb, we are safe in say- 

 ing the breed would soon run out. 



We have seen that the lobster breathes by gills on the 

 outside of the body. "With insects all this is changed. 

 They do not, however, draw in the air through their 

 mouth, but inhale it through minute openings on the side 

 of the chest and hind body. There are in the locust ten 

 pairs of these holes or "spiracles;" two pairs on the tho- 

 rax, and the remainder on the sides of the abdomen. They 

 are hard to find at first, but may be detected with the aid 

 of Fig. 98, where they are distinctly pointed out. The 

 air enters these holes, and is carried all over the body by 

 air-tubes, which are fine chitinous tubes, kept open by a 

 series of short elastic spiral thickenings, the tubes being 

 enveloped by the tracheal hypodermis. 



