142 NORTH AMERICAN DIPTERA. 



this genus sometimes have habits simihxr to those of Comjiso- 

 ■myia. The blue-bottle and green-bottle flies have habits 

 identical with those of Calllphora^ but they are not so common. 

 The screw-worm fly, an insect common over nearly all of 

 North and South America, is a bright shining green or golden 

 green in color, but will be distinguished from the blue-bottles 

 by the presence of blackish stripes on the thorax. It depos- 

 its eggs, which hatch almost immediately, in decomposing 

 matter, as do other members of the family, but it will also lay 

 them in the ulcers of cattle, or wounds, or at the orifice of the 

 human nose, especially when attracted thereto by a fetid breath. 

 The larvte in these cases quickly penetrate within the nasal 

 and frontal sinuses, sometimes to the number of a hundred or 

 more, quickly producing fever, extended ulceration and in fre- 

 quent cases, death. These cases of Myiasis, as the affection 

 is called, are not very frequent in North America, but have 

 been not seldom recorded from South America. Sareophila 

 WohlfaJirti, a European species, has similar habits. 



The group of Stomoxyiuce includes the common stable or 

 cattle-fly, the horn-fly and the famous tsetze fly of Africa and 

 Australia, all of which lay their eggs in fresh dung. The 

 horn-fly is a recent introduction from Europe, and has now 

 extended over nearly all of the United States. An allied spe- 

 cies, Ha-mafohla aids Snow, lives among the moose of the 

 northern woods. The tsetze fly is perhaps the most famous 

 of the group. Its bite is so poisonous that the regions which 

 it inhabits are rendered impassable for horses and dogs, 

 though it is less troublesome to other animals. 



The larvae of 3Iuschi.a have been found in decaying veg- 

 etables, dung, fungi and the larvae of various lepidoptera. 

 The larvae of (Ivapltomijiu and Mesmihrhia have been found 

 in cow and horse dung. 



The following table is that of v. d. Wulp (Biol. Centr. 

 Amer. Dipt, ii, 291) with the addition of those genera not yet 

 known from Central America. 



