AMERICAN DIFTERA. 269 



A Contribution to the ^tudy of American 

 DOLICHOPODID^. 



BY J. M. ALDRICH. 



TABLE OF GENERA. 



1. Fourth longitudinal vein with a widely divergent fork on the front side. . .2. 

 Fourth longitudinal vein generally without fork ; if one is present it is nearly 



parallel with the main vein 4. 



2. Cilia of tegulse hlack, third vein converging to the f<iurtli at tip, scutelluni 



with four large bristles Psilopodinus Bigot. 



Cilia of tegulje pale, third vein parallel with fourth at tip, scutelluni with two 

 large and usually two small bristles 3. 



3. Face wide, vertex deeply excavated Agono^onia Gueriu. 



P''ace narrow, vertex scarcely excavated L<eptorIietliuni Ahlrich. 



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



thorax, face very wide, vertex deeply excavated. 



Mesorhaga Schiner. 

 Head and thorax not as described n. 



5. Fourth vein bent forward, forming an ai)ical cro.ss-vein ; jiosterior cross-vein 



oblique, parallel with the margin of the wing. 



Pla$(ioneuruK Loew. 

 Posterior cross-vein nearly transverse, usually no apical cross-vein 3. 



6. Hind metatarsi witli large bristles above DoIieliopu»$ Latreille. 



Hind metatarsi without large bristle above 7. 



7. Hypopygium long, extending forward under the venter 8. 



Hypopygium short, not extending forward under the venter 20. 



8. Arista plumose 9. 



x\rista bare or pubescent 11. 



9. Face wide, bulging on the lower part Pelastoiieurus Loew. 



Face narrow 10. 



10. Third antennal joint of niale large, elongate, excavated above 



Leptoeorypha Aldrich. 

 Third antennal joint short, normal ^areionus Aldrich. 



11. Before the scutelluni the posterior third of the dorsum is hollowed out, or at 



least distinctly flattened 12. 



Before the scutellum convex as usual 15. 



12. Posterior cross-vein distant, much more than its own length from the margin 



of the wing (measured on the fifth vein) 13. 



Posterior cross-vein distant about its own length from margin 14. 



13. Second antennal joint prolonged along the inner side of the third. 



Cceloglutuiii Aldrich. 

 Second antennal joint not so prolonged, or forming a cup for the third. 



Tliryptieu»i Gerstaecker. 



14. Third and fourth veins parallel towards the tip; maritime specnes. 



Apiirosylus Walker. 

 Third and fourth veins convergent; found on bark of trees. 



Medeterus Fischer. 



TRANS. AM. ENT. SOC. XXX. SKPTEMBKR. 1904. 



