9 o 



NORTH AMERICAN DIPTERA. 



ANISOMERINI. 



1. Three posterior cells; two submarginal cells (13). Anisomera, 

 Four or five posterior cells; antennae of the $ sometimes much 



elongated. .......... 2 



2. The stigma occupies nearly the whole space between the tip of the 



auxiliary vein and the marginal cross-vein. . Eriocera. 

 The stigma occupies but a small portion of the space between the 



tip of the auxiliary vein and marginal cross-vein. 



Penthoptera. 



AMALOPINI. 



1. Antennae composed of thirteen joints ..... 2 

 Antennae composed of sixteen or seventeen joints. . . 5 



2. Two cross-veins between the first longitudinal vein and the anterior 



branch of the second vein. ....... 3 



Only one cross-vein between these veins. .... 4 



3. Front with a gibbosity behind the antennae (2). . Dicranota. 

 Front without gibbosity. ..... Polyangseus. 



4. Five posterior cells; both branches of the fourth vein furcate (14) . 



Khaphidolabis . 

 Four posterior cells; the posterior branch furcate. Plectromyia. 



5. Four posterior cells; wings pubescent. .... Ula. 

 Five posterior cells; wings bare. ...... 6 



6. Anterior cross-vein nearly at right angles with the longitudinal axis 



of the wing. ......... 7 



Anterior cross-vein at a very oblique angle with the longitudinal 

 axis of the wing, and parallel with the posterior cross-vein 

 (p. 80, 1) Pedicia. 



7. Rostrum much longer than the head. . . . Ornithodes. 

 Rostrum shorter than the head (4) .... Amalopis 



CYLINDROTOMINI. 



1. Five posterior cells; colors yellow and black. Cylindrotoma. 

 Four posterior cells. ......... 2 



2. Antennal joints subcylindrical, elongated. .... 3 

 Antennal joints subglobular; head and thorax conspicuously punct- 



ulate ......... Triogrna. 



3. Colors yellow and black. ...... Liogma. 



Colors brownish and grayish. .... Phalacrocera. 



