PEOC. EXT. SOC. WASH., VOL. 20, XO. 9, DEC., 1918 193 



Some hesitancy is felt in proposing a new genus for the reception 

 of this form because of its evidently strong affinities with Chry- 

 sops, but it differs so markedly in habitus from any species of 

 Chrysops known to the author, that it seems inadvisable to in- 

 clude it therein, especially as the form possesses structural char- 

 acters by which it may be distinguished from Chrysops. 



Chrysops Meigen. 



These are the so-called deer-, sheep-, or pine-flies. They are 

 black or black and yellow flies, usually with conspicuously marked 

 wings. They frequent at least partially shaded situations and 

 most of them swarm about moving warm-blooded animals, seek- 

 ing an opportunity to bite. In the case of man, at least, they 

 usually desert their intended victim when he comes to rest. 



Key to the Species.' 



A. Abdomen mostly dark. 



B. Wing with more or less distinct dark markings. 



C. Apex of wing beyond crossband more or less distinctly infus- 



cated especially bordering costal margin. 



D. Apical spot consisting of a linear band along costal mar- 

 gin, barely extending into second submarginal cell, hya- 

 line triangle extending broadly across first submarginal 



cell brimleyi 



DD. Apical spot occupying at least four-fifths of second sub- 

 marginal cell. 



E. Abdomen immaculate; length about 8 mm panulus 



EE. Abdomen with one or more yellowish stripes. 



F. Hyaline triangle barely extending to the fir<r 



submarginal cell univittatus 



FF. Hyaline triangle extending nearly to costal 

 margin. 



G. Apical spot encroaching on first posterior cell: 

 hyaline triangle semilunate. Abdomen dark 

 brown bearing 3 obscure yellowish stripes 

 in the variety morosus, one in the typical 



form , lugens 



GG. Apical spot not touching first posterior cell: 

 hyaline triangle wider. Abdomen with a 

 single median yellow stripe obso 1 ' 



3 The key includes C. indits and C. mitis which have been collected at 

 Potomac Run, Va. and which may occur in this fauna. 



