128 NORTH AMERICAN DIPTERA. 



o. Cheeks broader than the long diameter of the eyes ; oral border mod- 

 erately protuberant; costa somewhat spinose. . Actoka Meigen. 

 Cheeks not broader than the long diameter of the eyes; oral margin 

 very prominent ; costa bare. .... Dryomyza Eallen. 



4. Hind femora long : second antennal joint much elongated, longer than 



the third. ........... 5 



Hind femora only moderately elongated and but little thickened ; second 

 antennal joint as long or a little shorter than the third. 



Tetanocera Latreille. 



5. Hind femora thickened; face not produced downward. 



Sepedon Latreille. 



Hind femora not thickened ; face nmch produced downward (Central ? 



and South America). Thecomyia Perty. 



50. PHYCODROMIDvE. 



Pleurae, scutellum and abdomen flat. Front bristly ; cheeks 

 and face bristly, the vibrissae indistinctly differentiated. Legs 

 stout, all the tibiae spurred and with a preapical bristle on the 

 outer side; metatarsi not abbreviated; terminal joint of all 

 the tarsi incrassate and withmrt claws. Neuration of wings 

 complete ; auxiliary vein distinct in its entire course ; costa 

 without bristles ; basal cells not small. 



But a single genus of this family is known to occur in 

 North America, Cadopa Meigen. Members of it are found in 

 great abundance among sea-weed and other algse thrown up 

 bv the waves along the sea-shore. 



51. SCATOMYZID^. 



Tegulae small, the upper one concealing the lower one. 

 Head rounded, eyes round, bare, broadly separated by the 

 front in both sexes. Wings large ; auxiliary vein always pres- 

 ent, the costa never with bristles at its termination, three 

 basal cells always present ; first posterior cell never narrowed 

 or closed. Abdomen with more than four segments. 



The flies of this groxip are easily confounded with the 



