POISONOUS INSECTS AND THEIR RELATIVES 425 



lays its eggs in a wound on some animal or in decaying 

 animal matter. A single fly may deposit three or four 

 hundred eggs in a very few moments. The eggs hatch 

 within a few hours and the maggots burrow into the 

 tissues of the wound or into the decaying mass. The 

 flies are a great pest to cattle, and other domestic animals, 

 for when an opportunity occurs, the eggs are deposited in 

 flesh wounds or sores, where the maggots cause serious 

 injury. When the mag- 

 gots are mature, they fall 

 to the ground, w r here they 

 bury themselves and 

 pupate. The life cycle 

 may be passed in two to 

 three weeks. 



The attacks of this pest 

 on man are usually made 

 by a deposition of eggs in 

 the nostrils or mouth while 

 the victim is asleep. Snow 

 has related several cases FIG. 147.- Screw worm fly. ~< X 3j.) 

 of infestation of man by 



this fly. In most of these cases the patients were 

 sufferers from catarrh, which may account for the attrac- 

 tion of the flies. Also, in most of the cases where the facts 

 were known, the eggs had been deposited in the nostrils 

 or mouths of the patients while asleep. In one case, a 

 fly attacked a man while riding in a buggy and deposited 

 eggs in his nose before he could prevent it. In most of the 

 cases the maggots burrowed through the tissues of the 

 nose, mouth, and soft palate, even honeycombing the 

 bones, and generally proved fatal to the victim. 



