270 J. M. ALDRICH. 



15. The ffiee of the male extends below the eyes, hanj^itiK flown before the 



mouth, apron like Pol.Viiie(loii Osten Sacken. 



The face of the male reaches ahoiit as fur as the lower edge of tlie eyes; head 



vertically enlonjjated Tachytrecliiis Stannius. 



Face of the male reaching as far as the lower edge of the eyes, hut the head 



not elongated ParacliiiN Loew. 



16. Third and fourth veins parallel towards the ti]> •■■ 17- 



Third and fourth veins distinctly convergetit 19. 



17. Bristles of thorax yellow Tlirypticiiw Gerstaecker. 



Bristles of thorax black 18. 



18. First antennal joint bare above PelorO|»eo<Ies Wheelei-. 



First antenna] joint hairy above CiiyninopterniiS Loew. 



19. The last segment of the fourth vein graduall.v appioaching the third. 



HereOiiitoniiiN Loew. 

 Last segment in the middle abruptly curving forward, then gradually resum- 

 ing its former course, ending near the third vein. 



Paracliiis Loew. 



20. Costal vein extending only to the tip of the third vein, the latter part of the 



fourth vein evanescent ■ ■ - Asyii<letiiS Loew. 



Costal and fourth veins normal 21. 



21. First antennal joint hairy above 22. 



First antennal joint bare above 26. 



22. Fourth vein towards the tip strongly curved towards the the third, nearly 



reaching it in the margin PelaKtoneiiriiS Loew. 



Fourth vein parallel with the third, or slightly convergent 23. 



23. Arista dorsal, face very narrow, palpi small Anepsins Loew. 



Arista dorsal, face wide, palpi large 24. 



Arista nearly or quite at the tip of the large, pointed third joint 25. 



24. Arista plumose Phylarclilis Aid rich. 



Arista pubescent I>iosl racus Loew. 



25. Proterior cross-vein distant about its own length from the end of the fifth 



vein Hypocharassiis Mik. 



Posterior cross-vein much more than its own length from tip of fifth vein. 



Argyra Macquart. 



26. A concave or distiuctl.v flattened, bare space before the scutellum 27. 



Thoracic dorsum convex as usual 31. 



27; Bristles of thonix pale yellow ChrysoliiuUM Loew. 



Bristles black, rarely brownish 28. 



28. Fourth vein parallel with the third beyond the cross-vein, or nearly so. .29. 

 Fourth vein converging towards the third, either gradually or by a double 



curve .... Keiiri^oiia Rondani. 



29. Acrostichal bristles present only at the anteiior edge of thorax, very mi- 



nute Xaiitlioclilorus Loew. 



Acrostichal bristles well developeii. two-rowed 30. 



30. Very minute, blackish, opaque species AchalcuM Loew. 



Small, yellow species XHiithiiia Aldrich. 



■■■" Thrypticus minor Aid. from St. Vincent, W. I., has the 3rd and 4th veins some- 

 what convergent. 



