AMERICAN DIFTERA. 269 



A Contribution to the Study of American 

 DOLICHOrODIDJB. 



BY J. M. ALDRICH. 



TABLE OF GENERA. 



1. Fourtli longitndiual 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 black, third vein converging to the fourtli at tip, scutelluni 



with four large bristles Psilopodinus Bigot. 



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

 large and usually two small bristles 3. 



3. Face wide, vertex deeply excavated Agouosonia Guerin. 



Face narrow, vertex scarcely excavated Leptorhetlium Aldri<'h. 



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



thorax, face very wide, vertex deeply excavated. 



Alesorhaga Hchiner. 

 Head and thorax not as described 5. 



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



oblique, parallel with the margin of the wing. 



Plagioneurniii Loew. 



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



ti. Hind metatarsi with large bristles above Dolicliopiiisi 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. 



Arista bare or pubescent 11. 



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



Face narrow 10. 



10. Third anteunal joint of male large, elongate, excavated above 



Lieptoeorypha Aid rich. 

 Third anteunal joint short, normal Sarcionus 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 anteunal joint prolonged along the inner side of the third. 



Coeloglutu!^ Aldrich. 

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



Thrypticus Gerstaecker. 



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



Aphrosylus Walker. 

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



Medeterns Fischer. 



TRANS. AM. BNT. SOC. XXX. SKPTEMBER. 1904. 



