330 



A COURSE ON ZOOLOGY. 



FIG. 289. 



sprinkling of the plants with the arsenical compound 

 Paris green. It is about a third of an inch long, light- 

 brown, with dark spots. The 

 fire-fly produces its brilliant light 

 by two spots on the thorax. 

 The glow-worm has its phos 

 phorescent organs on the ab- 

 domen, and only the males are 

 winged; the cause of the phos- 

 phorescence is not known. 



Among orthoptera, the better 

 known are the grasshopper, the 

 cockroach, the migratory locust, 

 and the cricket. Many of this 

 order are jumping insects, and in 

 he' males can produce a 



of mole-cricket, showing peculiar rasping sound by rub- 



nous projections on the posterior 

 legs. This faculty has often occasioned confusion of the 

 grasshoppers with the common locust. The migratory 



FIG. 290. 



GREEN- FACED LOCUST (Tragocephala viridifasciata). 



locust is a great destroyer of crops; sometimes these 

 insects appear in vast clouds that alight and devour 

 every green thing before them, leaving fields naked. 

 The cicada common locust belongs to the order of 



