FAMILY TACHIXID.E — THE TACHIXIDS 427 



56. Ultimate section of fifth vein not over one-third as long as the pie- 



ceding- section, or the parafacials without bristles 58 



Ultimate section of fifth vein at least half as long as the preceding 

 section; parafacials with one or more proclinate bristles 57 



57. Inner end of posterior crossvein lying immediately behind the an- 



terior crossvein Plagia Meigen 



Discal crossvein lying well beyond the anterior crossvein. 



Cyrtophloeba Rondani 



58. Fourth vein angulate or with sharp curve; abdomen with strong- 



bristles 59 



Fourth vein approaching the third in a gentle curve; abdomen with 

 only weak bristles apically Gymnophania Brauer & Bergenstamm 



59. Parafacials without bristles along their inner edges, sometimes with 



bristly hairs along their middle (51 



Parafacials with a row of bristles along their inner edges 60 



60. Basal two aristal segments short; antennae simple in both sexes 60a 



Basal aristal segments very elongate; third antennal segment of male 



composed of two or three arms (103, 104) Dichocera Williston 



60a. Third antennal segment but little longer than the second. 



Muscopteryx Townsend 

 Third antennal segment several times as long as the second (42, 43, 

 45, 52, 96 ) Paradidyma Brauer & Bergenstamm 



61. Parafacials without strikingly long hair, or it is irregularly spaced.. . . 62 

 Parafacials with the haiis arranged in a median series and increas- 

 ingly long and strong below *Eulasiona Townsend 



62. Bend of fourth vein with at most a distinct fold 63 



Bend of fourth vein with a long appendage. 



Metopomuscopteryx Townsend 



63. Three pairs of presutural acrostical bristles or three presutural dor- 



socentrals Lydina Desvoid}' 



At most two pairs of presutural acrostical bristles 64 



64. Two pairs of presutural acrosticals and dorsocentrals (35, 139). 



Myiophasia Brauer & Bergenstamm 

 A single pair of presutural acrosticals and two pairs of dorso- 

 centrals. Townsendina, n. g. 



65. Facial ridges without strong bristles 69 



Facial lidges with strong bristles on lower half or more 66 



66. Parafacials not wider than antennae 67 



Parafacials much wider than antennae; oral margin scarcely produced. 



Myiopharus Brauer & Bergenstamm 



67. Arista long plumose Comyops Wulp 



Arista at most very short plumose 68 



68. Ocellars strong; face not strongly retreating below; female piercer 



as long as the abdomen Spathimyia Townsend 



Ocellars absent or hairlike; face strongly retreating. 



Paralispe Brauer & Bergenstamm 



* Cuiran, lO'iT, Bull. Biooklyn Ent. Sor., xxii, ii. 149. 



