232 



NORTH AMERICAN DIITKRA. 



TABLE OF GENERA. 



i. Fourth longitudinal vein with a widely divergent fork on the front 



side (1, 8) 2 



Fourth longitudinal vein generally without fork; if one is present 

 it is parallel with the main vein. ..... 4 



2. Cilia of the tegulae black, third vein converging to the fourth at 



tip (3), scutelluin with four large hristles (b). Psilopodinus. 

 Cilia of tegula- pale, third vein curving forward at tip (1), scu- 

 telluin with two large and generally two small bristles. . 3 



3. Face wide, vertex deeply excavated (a). . . Psilopus. " 

 Face narrow, vertex scarcely excavated. . Leptorhethum. 



4. Thorax almost as broad as long; head wider than its height or than 



the thorax: face wide, vertex deeply excavated (17, 32 1 . 



Mesorhaga. 

 Head and thorax not as described. ...... 5 



5. Fourth vein bent forward, forming an apical cross-vein; posterior 



cross-vein oblique, parallel with the margin of the wing (6, b). 



Plagioneurus. 



Posterior cross-vein nearly transverse, usually no apical cross- 



vein, ........... 6 



b. Hind metatarsi with large bristles above (35, a, b, d). 



Dolichopus. 

 Hind metatarsi without large bristles above. ... 7 



7. Hvpopvgium long, extending forward under the venter (33). 8 

 Hypopvgium short, not extending forward under the venter 



(34, one form). 20 



8. Arista plumose (27) ' . . . • 9 



Arista bare or pubescent. . . . . . . 11 



9. Face wide, bulging on the lower part 1 27, 31, 14, a, d). 



Pelastoneurus. 

 Pace narrow. .......... 10 



10. Third antenna! joint of male large, elongated, excavated above. 



Leptocorypha. 

 Third antenna] joint normal, as in fig. 27. . . Sarcionus. 



1 1 . before the scutellum the posterior third of the dorsum is hollowed 



out, or at least distinctly flattened 12 



Before the scutellum convex as usual. ..... is 



* . \gonosoma of my Catalogue, iqo.S. 



