236 



ELEMENTARY ENTOMOLOGY 



nuisances. Very similar and almost indistinguishable from the 

 house-fly is the common stable-fly, so annoying to cattle. The mouth- 

 parts of the females are fitted for piercing. Just before a storm 

 these flies frequently come into houses and annoy us, from which 

 comes the saying that flies bite before a storm. Like those of the 

 housefly, the larvae live in fresh horse manure. The little horn-flies 

 often annoy cattle by assembling on their flanks and clustering at 

 the base of the horns. The maggots develop in cow manure. 



The flesh-flies (Sarcophagidae) are so called because many of them 

 lay their eggs on the bodies of dead animals or in open wounds, 



FIG. 375. The horn-fly. (Enlarged) 

 <7, egg ; /', fly ; c and d, head and mouth-parts. (After J. B. Smith) 



though some of the larvae live in dung and decaying vegetable 

 matter. The common flesh-fly (Sarcophaga sarracenid] looks like 

 a very large house-fly and gives birth to live maggots (the eggs 

 hatching in the body of the female), which are deposited on fresh 

 meat or in open wounds. The blow-flies and blue-bottle flies are 

 about the size of house-flies,- with the abdomen steely-blue or green- 

 ish, and lay their eggs on meat, cheese, or other provisions, which 

 are said to be " blown." The eggs hatch in a day ; the maggots feed 

 on the juices t>f decaying meat and become full grown in a few 

 days. The common blue-bottle or green-bottle fly (Lncilia caesar) 

 also lays its eggs on cow dung. The screw-worm fly (Chrysomyia 

 macellaria) is a bright, metallic green, about one third of an inch 



