Screw- WORMS and other maggots. 15 



winter, or early spring months. These blowflies usually are larger 

 in size, more hairy in appearance, and have grayish colored thoraxes 

 and dark-blue or silvery blue abdomens. 



The breeding habits of- the black blowfly are very similar to those 

 of the screw-worm fly. It is exclusively a flesh breeder, but occa- 

 sionally it may develop in very old decaying carcasses. The eggs, 

 which are deposited in masses, hatch in from less than 24 hours to 4 

 days. The maggots become fully developed in 3 or 4 days after 

 hatching and begin to crawl away and burrow into the earth. The 

 pupa stage lasts from 7 to 10 days, and after the fly emerges a week 

 or more usually elapses before the first eggs are laid. On living 

 animals the rate of development is probably somewhat faster. Bv 

 this rapid breeding the flies may become very abundant during the 

 early fall before cold weather sets in. 



THE GREEN-BOTTLE FLY/ 



The green-bottle fly has a wide distribution throughout the world. 

 It is known as the green-bottle or green blowfly in this country. It 

 is rather closely associated with 

 habitations of man and is not 

 as commonly found on the range 

 as are the screw-worm fly and 

 the black blowfly. It is often 

 abundant in cities, especially if 

 garbage is not properly cared for. 



This is the fly which causes 

 the wool-maggot of sheep in 

 the British Isles, and the same 

 habit has been recorded for it 

 in this country. It has been 

 known to deposit eggs on the 

 soiled rumps of calves as well 

 as sheep, following diarrhea, and 

 occasionally it infests wounds 

 on animals, but it is not as in- 

 jurious as are the two species 

 previously described. 



Ir is usually slightly smaller 

 than the black blowfly and the 



Fig. 6. — The black blowfly or common 

 wool-maggot fly of the United States, 

 as seen from above. Enlarged. 



^LuciUa nericata Meigen. 



