3 i6 NORTH AMERICAN DIPTERA. 



The flies of this family are almost invariably found 

 about decomposing organic matter. Those belonging to 

 Borborus and Sphccroccra are observed, often in clouds, 

 about dung and refuse, where their larvae live. The 

 small flies of the genus Limosina are seen in abundance 

 in marshy places in company with the smaller ephydrids. 



The larvae of Borborus are cylindrical, with the skin 

 roughened by erect, minute bristles; the antennae are 

 two-jointed, the mouth-hooklets well developed; the pos- 

 terior end has conical processes near the anus, and small- 

 er tubercles about the spiracles; in Limosina the hind 

 stigmata are tube-like. The larvae of Limosina live in 

 fungi, algae, diseased potatoes, and perhaps water. 



TABLE OF GENERA. 



i. Wingless species, Aptilotus. 



Wings fully developed 2 



2. Fourth and fifth longitudinal veins incomplete or obsolescent be- 



yond the discal cell; second basal cell incomplete (2, 3, 4, 5). 



Limosina. 



Fourth vein at least, fully developed; second basal and the anal 



cells complete 3 



3. Scutellum with well-developed bristles; fifth vein incomplete be- 



yond discal cell; metatarsi shorter than second joint (6, 7, 81. 



Borborus. 

 Scutellum without bristles; fifth vein complete (1). Sphserocera. 



