324 



APPLIED ENTOMOLOGY 



and pupae or drive away the adults, particularly when sprinkled around 

 in stables. Hauling the manure directly to the fields and spreading it 

 there, when practicable, preserves more of its value than letting it stand 

 in piles where leaching and other processes going on reduce this. The 

 destruction of garbage and of the organic matter at public "dumps," 

 in which flies breed, is also important. Screening houses, food and gar- 

 bage pails or cans and trapping the adult flies either by poisoned or sticky 

 fly papers or by the use of fly traps are all methods for reducing the fly 

 pest which, when these insects are abundant, should be made use of. 



Almost any fly having habits similar to those of the house-fly may be- 

 come a disease carrier in a similar way, and the above methods are of 

 value against them all. 



Some of the flies in this family lay their eggs on meat, either decaying 

 or fresh, which is then spoken of as " blown." The flies which do this 

 are usually the ones commonly called " blue-bottle " and " green-bottle " 

 flies. 



m 



FIG. 343. Screw- worm Fly (Chrysomyia macellaria Fab.), greatly enlarged. (From 



U. S. D. A. Farm. Bull. 857.) 



The Screw-worm Fly (Chrysomyia macellaria Fab.). This pest occurs in 

 South America and northward into Canada. It is a serious pest to live stock and 

 other animals, chiefly in the Southwestern States, though occasionally it becomes 

 important farther north and east. 



The adult fly (Fig. 343) is of a dark bluish-green color and has three black 

 stripes along its back. It is considerably larger than the house-fly. Its eggs 

 are laid in any decaying animal matter and also in wounds such as are caused 

 by barbed wire, hooking, etc., in living animals. The larvae (Fig. 344) hatch in 

 from a few hours to a day or two and burrow into the tissues, if the eggs were laid 



