338 NORTH AMERICAN DIPTERA. 



tion wherever man exists. Other species, which are 

 scarcely less common and widely distributed, are the 

 common blue-bottle and blow-flies, members of the gen- 

 era Lurilia and Calliphora. As widely known are the 

 stable -fly or cattle -fly, Stomoxys, and the horn -fly, 

 Hccmatobia. 



• 



The larvae of the house-fly live, for the most part, in 

 dung or manure, but will thrive in almost any kind of 

 filth; I have reared them from the decaying material in 

 the bottoms of spittoons filled with tobacco. The female 

 lays about one hundred and twenty-five eggs, which 

 hatch in one or two days, according to the weather. The 

 larvae attain their full development in from four to seven 

 days, and then, crawling into some secluded place, trans- 

 form into pupae, from which they emerge in about six 

 days as mature insects, those of the autumn broods re- 

 maining over winter as puparia. In partially secluded 

 spots the mature fly will sometimes survive the winter. 

 The cluster-fly, Pollcnia rudis, is yet more remarkable in 

 this last respect. Often in early spring, or even during 

 mild days of the winter they may be observed crawline 

 about over the snow in numbers. They are stupid and 

 slow and have received the name of cluster-flies from 

 their habit of congregating in clusters about dwellings. 

 They resemble a blow-fly somewhat; but will be distin- 

 guished by the presence of short, depressed, sparse light- 

 colored hairs on the thorax. The larvae of species of 

 Calliphota, especially of C. vomitoria, are better known, 

 perhaps, than those of any other insect. They are the 

 common blow-fly maggots of fresh and decaying meats 

 and vegetables. The cooking of corned beef or tin nips 

 or cabbages during warm weather is sure to attract num- 

 bers of these insects, which are quite noticeable for their 

 loud humming and headlong flight. In the arid regions 

 of northern Wyoming the writer has seen them in extra- 



