90 NORTH AMERICAN DIPTERA. 



A.NISOMERINI. 



i. Three posterior cells; two submarginal cells (13 1. 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. 

 i. 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 Polyang-aeus. 



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



Rhaphidolabis. 

 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. ' 



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 



CYLIXDROTOMIXI. 



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

 Four posterior cells 



2. Antennal joints subcylindrical, elongated 3 



Antenna! joints subglobular; head and thorax conspicuously pnnct- 



ulate ' Triogma. 



3. Colors yellow and black Liogma. 



Colors brownish and grayish Phalacrocera. 



2 



