190 



PROC. ENT. SOC. WASH., VOL. 20, NO. 9, DEC., 1918 



uniform a region as that of the District of Columbia probably 

 never will produce an equal number of Tabanid species. A 

 tabulated comparison of the two faunas follows: 



* One name exul, is a synonym. 



Haematopota punctulata, and an additional species of Tabanus 

 namely fuscopunctatus have been taken at Chesapeake Beach, 

 Md., and two additional species of Chrysops (indus and mitts') 

 have been collected at Potomac Run, Va. All of these very pos- 

 sibly may yet be taken within the limits of the District fauna. 



Special effort has been made by a number of local entomolo- 

 gists to collect the fauna of Plummers Island, Md., and vicinity. 

 So far 21 species of Tabanidae have been taken on this 12-acre 

 island, and 17 additional species in nearby parts of the Potomac 

 River Valley. When the occurrence of species on Plummers 

 Island is not stated in the text, it is indicated by the initials 

 P. I. in parenthesis following the account of the species, and in 

 the same way V. P. I. meaning vicinity of Plummers Island is 

 added when necessary. 



Key to Genera. 



A. Hind tibiae with 2 short but definite spines. at tip. 



B. Third joint, of antenna with 8 divisions faintly indicated. 



C. Wings distinctly divided into anterior colored and poste- 

 rior hyaline portions; female pale sericeous, abdomen 



broad and obtuse Goniops 



CC. Wings uniformly hyaline or smoky; body color darker, 



abdomen longer and more pointed Pangonia 



BB. Third joint of antenna with 5 divisions. 



