454 NORTH AMERICAN DIPTERA 



Tergites not produced downward, the edges rarely setulose; ovipositor 

 not elongate 340 



340. Face narrower than either eye; penultimate arista! segment short 



(149, 173) Elodia Desvoidy 



Face wider than either eye; penultimate aristal segment elongate. 



Schizotachina Walker 



341. Apical crossvein present 347 



Apical crossvein absent 342 



342. Posterior crossvein present 343 



Posterior crossvein absent Phytomyptera Rondani 



343. Antennae reaching the lowest fifth of the face 344 



Antennae not reaching below the lowest third of the face. 



Hemithrixion Brauer & Bergenstamm 



344. A single bristle at the base of the third vein 345 



Three or more bristles on the third vein 346 



345. Parafacials narrower than the third antennal segment. 



Schizotachina Walker 

 Pai'afacials twice as wide as the third antennal segment. 



Roeseliopsis Townsend 



346. Antennae arising near upper edge of eyes, enormovis in size; head 



almost rectangular; bristles of thorax not unusually depressed (28, 



29, 144 ) Euryceromyia Townsend 



Antennae arising lower down; head not nearly i-ectangular; bristles of 

 thorax depressed (148, 189) Actia Desvoidy 



347. Palpi present and well developed 354 



Palpi absent or but little longer than the width of the proboscis at 



point of attachment 348 



348. Arista bare or pubescent 349 



Arista plumose; face strongly carinate Prosena Serville 



349. Third antennal segment usually less than three times the length of 



the second, if long the abdomen pedunculate 350 



Third antennal segment five times the length of the second, broadened 

 apically, concave above (47, 70) Beskia Wulp 



350. Apical cell open 351 



Apical cell closed and petiolate (54) *Cylindromyia Latreille 



351. Face not conspicuously receding, concave in profile, the oral margin 



produced; vibrissas situated well above the oral margin 352 



Face receding; oral margin not produced; vibrissae level with oral 

 margin (63, 64 ) Icelia Desvoidy 



352. Second abdominal segment strongly narrowed Polistiopsis Tov^^nsend 



Second abdominal segment not narrowed, much bi-oader than deep. . . .353 



353. Palpi entirely absent Paraphasiopsis Townsend 



Palpi narrow, four times as long as wide, or longer. .Phasiopsis Townsend 



Aldiich, 1926. Pr. U. S. N. M., Ixviii. Art 23, pp. 1-27. 



