252 NORTH AMERICAN DIPTERA. 



TABLE OF C.ENERA. 

 i. Antennae with a terminal style 2 



Antennae with a dorsal (rarely snhterminal) arista. . . 4 



2. Antennae cylindrical, the first two joints elongated; first posterior 



cell with a stump of a vein (24) [Ceria). Sphyximorpha. 

 First two joints of the antennae short 3 



3. Eyes hare; small species. Pelecocera. 



Eyes pilose; larger species. ..... Callicera- 



4. Marginal cell of the wings closed and petiolate. ... 48 

 Marginal cell open. ........ 5 



5. Anterior cross-vein of the wings distinctly hefore the middle of 



the discal cell; almost always rectangular. ... 6 



Anterior cross-vein near or beyond the middle of the discal cell, 



usually oblique. ......... 55 



6. Antennae elongate (if arista plumose, see 56). ... 7 

 Antennae short. '14 



7. Mesonotum with yellow lateral stripes; large species, the abdo- 



men always with distinct yellow bands (23, 41). 



Chrysotoxum. 



Mesonotum not with distinct yellow lateral stripes or margins. 8 



8. Face rounded, not tuberculate, pilose; oral margin not project- 



ing 9 



Face not evenly arched; tuberculate or the oral margin project- 

 ing I2 



9. Moderately large to large species; scutellum flattened, often with 



spines or tubercles on its border; a stump of a vein in the first 



posterior cell from the third longitudinal vein. . . 10 



Small species; scutellum without spines; no stump of vein in first 



posterior cell (30) Pipiza. 



10. Abdomen much narrowed at the base. . . . . .11 



Abdomen not or but little narrowed at base (1). Microdon. 



11. Face swollen and prominent below. . Rhopalosyrphus. 

 Face not swollen and prominent below. . . Mixogaster. 



12. Body clothed with sparse (omentum; all the femora thickened and 



with spinous bristles below [Leprotnyiafi) . Lepidostola. 



Body not clothed with flattened tomentum; the femora not thick- 

 ened with spinous bristles below. ..... 13 



13. Face partly or wholly yellow, tuberculate below, the epistoma not 



projecting; face and front not wrinkled (5, 7). Paragus. 



* The name Lepidostola Mik has slight priority over Lepromyia. 



