FAMILY TACHIXID.E THE TACHIXIDS 451 



299. Penultimate aiistal segment elongate Distichona Wulp 



Penultimate aiistal segment not over twice as long as wide. 



Vibrissovoria Townsend 



300. Cheeks not wider than the thii'd antennal segment 302 



Cheeks much wider than the third antennal segment 301 



301. Posterior tibiae evenly, closely ciliate; parafacials narrow; smaller 



species Sturmia Desvoidy 



Posterior tibi?e not closely ciliate; parafacials wide; large species. 



'^Belvosia Desvoidy 



302. Both sexes with reclinate orbital bristles 303 



Neither sex with reclinate orbitals Prosopaea Rondani 



303. Ocellars entirely absent Pseudocha;ta Townsend 



Ocellars very small but distinct and cruciate; male with two reclinate 



and one proclinate orbital Argyrochsetona Townsend 



304. Apical crossvein present 306 



Apical crossvein absent 305 



305. Parafacials much wider than antennae Roeseliopsis Townsend 



Parafacials very narrow below Schizotachina Walker 



306. Posterior tibiae not ciliate, or if so the bristles are rather widely 



separated with two or more of them longer or the parafacials are 



not hairy below the frontal bristles 308 



Posterior tibi« evenly closely ciliate, at most one of the bristles con- 

 spicuously longer than the rest; parafacials usually haired on the 

 upper half 307 



307. Cilia on posterior tibiae long, very dense and contiguous; parafacials 



usually with hairs below the f rentals (Thysanopsis Tns., Blephari- 



peza Macq.) (4) Leschenaultia Desvoidy 



Cilia less numeious, not quite contiguous; parafacials bare (109). 



fAchaetoneura Brauer & Bergenstamm 



308. Frontal bristles extending but little below the base of the third anten- 



nal segment, usually a single bristle below the base; fourth vein 

 without a fold or the facial ridges bristled on more than the lower 



half 309 



Frontals extending to the middle of the third antennal segment, at 

 least two bristles below the base of the arista; eyes sparsely short 

 haired; bend of fourth vein with a long fold; facial ridges usually 

 bristled on the lowest third Exorista Meigen 



309. Middle coxse without stout apical spines 310 



Middle coxae with short, stout curved spines on the apex (?) (136, 137, 



153, 175) Doryphorophaga Townsend 



310. First vein with at most two or three weak bristles 311 



First vein bristled on at least the apical half . . . .Chaetophleps Coquillett 



311. Appendage or fold of fifth vein less than one-third as long as the 



preceding section 313 



Appendage or fold of fifth vein more than half as long as the preced- 

 ing section 312 



* Aldrifh, 1928, Proc. U. S. N. M.. Ixxiii, Article 8, pp. 1-45. 

 t Webber. 1930. Proc. U. S. N. M.. Ixxviii, Art. 10, pp. 1-37. 



