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 

 these the males can produce a 

 peculiar rasping sound by rub- 

 bing the wing-cases against spi- 

 nous projections on the posterior 



BRAZILIAN FIRE-FLY (Pyro- 

 phorus noctilucus) in burrow 

 of mole-cricket, showing 

 the two oval phosphores- 

 cent organs on the thorax. 



This faculty has often occasioned confusion of the 

 grasshoppers with the common locust. The migratory 



FIG. 290. 



GREEN- PACED LOCUST (Tragocephala viridtfasciata). 



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 



