224 N< )RTH AMERICAN DIPTKRA. 



5. Third longitudinal vein simple. ...... 6 



Third longitudinal vein branched. ...... 7 



6. Anal cross-vein parallel with the hind margin of the wing (13). 



Oreothalia. 

 Anal cross-vein perpendicular to the hind margin of the wing 16). 



Heleodromia. 



7. Head longer than broad, extending forward; wings brown with 



numerous pale spots. .... Dolichocephala. 

 Head transverse, nearly vertical. .... Clinocera. 



BRACHYSTOMATINiE. 

 Anterior branch of third vein terminates in the second vein (14i. 



Blepharoprocta. 

 The anterior branch of the third vein terminates in the costa. 



Bracbystoma. 

 HYBOTINjE. 



1. Fourth vein forked; hind femora slender. .... 2 

 The discal cell emits two simple posterior veins; hind femora more 



or less thickened; antenna; with a slender arista. . . 3 



2. Third longitudinal vein furcate; noantennal style 1 5, 10) Prorates. 

 Third vein simple; antennae with a thickened style. Meghyperus. 



3. The second vein arises near the base of the wing 1 25 1 . Syneches. 

 The second vein arises near the middle of the wing. . . 4 



4. Vein between basal cells indistinct. ..." Syndyas. 

 Veins between basal cells strong (1, 21) . . . . Hybos. 



OCYDROMIIN.K. 



1. Discal cell present. ......... 2 



Discal cell wanting. ......... 9 



2. The discal cell emits three simple posterior veins. ... 3 

 First po>terior vein obsolete; antennae with a long, slender arista. 8 



3. Third antennal joint short, ovate, pointed, with a long arista; third 



longitudinal vein simple. .... Parathalassius. 

 Antenna; with a short, thick style 4 



4. Third longitudinal vein furcate; last antennal joint short and broad. 



Hormopeza. 

 Third vein simple. .•.•..... 5 



5. Hind femora spinoss below, thickened; hind tibiae shortened, bow- 



ed near the knee; last antennal joint large. . Oedalea. 



