102 NORTH AMERICAN DIPTERA. 



prominent. Wings absent in Apterina; auxiliary vein absent ; 

 all three basal cells complete. Legs moderately long and 

 strong ; hind metatarsi dilated and abbreviated. 



The flies of this family are almost invariably found about 

 decomposing organic matter. Those belonging to the gen- 

 era Borborus and Sphcerocera are observed often in clouds 

 about dung and sewage, where their larvae live. The small 

 flies of the genus Limosina are observed about marshy places 

 in company with Ephydrids. 



The larvae of Borborus are cylindrical and conical, with 

 the skin roughened by erect, minute bristles ; the antennae are 

 two-jointed, the mouth-hooklets developed. The posterior 

 end has conical processes near the anus, and smaller tubercles 

 about the spiracles ; in Limosina the hind stigmata are elon- 

 gated into a tube. The larvae of Limosina live in algae, fungi, 

 diseased potatoes, etc. 



TABLE OF GENERA. 



1. Wingless species. '. APTERINA Macquart. 



Wings fully developed 2 



2. Fourth and fifth longitudinal veins incomplete beyond the discal cell, 



not reaching the border. .... LIMOSINA Macquart. 

 Fourth vein at least, fully developed . 3 



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



the discal cell. ....... BORBOIUJS Meigen. 



Scutellum without bristles; fifth vein complete. SPHCEROCERA Latreille. 



34. AGROMYZIM;. 



Front broad, with or without bristles. Antennae short, the 

 third joint usually rounded, sometimes moderately elongate, 

 or subquadrate ; oral vibrissee present, or absent. Arista 

 wholly wanting (Cryptochcvtum) or, when present, bare or pu- 

 bescent; never distinctly plumose. Genitalia rarely promi- 

 nent. Wings broad; auxiliary vein rudimentary or indistinct, 

 never distinctly separated in its whole length from the first 



