190 Annals Entomological Society of America [Vol. XI, 



29. Antennae, palpi and proboscis pale yellow; notum not densely pubescent; 



veins brown, the third vein straight, cf with the pedicel of the second 

 and third veins broadened to a black disk and with a stout flexor 



bristle near the end of the hind tibia; halteres yellow flavicornis. n. sp. 



Antennas and mouthparts black; mesonotum densely pubescent; veins 

 black, the third vein sinuous; cf not thus distinguished; halteres 

 black 30. 



30. Pygidium rounded, closed and without long hairs setulosa, n. sp. 



Pygidium open, asymmetrical, the right side projecting as a curled, 



black setulose lamella, the left side of the pygidium clothed with long, 

 black, hair-like bristles trichura, n. sp. 



31. Second antennal joint with a long seta beneath; hind femora with preapical 



bristles on the front side, hind tibiae with more or less developed 



apical spur 32. 



[Second antennal joint without a long seta; hind femora without preapical 



bristles, hind tibias with extensor bristles 39. 



32. Hind tibiae with a strong lappet and with a long extensor bristle at its 



middle but without subapical bristles; three preapical bristles on the 

 outside of the hind femora, hind metatarsi yellow-setulose beneath; 

 pubescence of the mesonotum long and pale, dorsocentrals present; 

 anterior cross- vein just before the middle of the discal cell; eyes 



nearly touching above the antennae spectabilis Melander 



Hind tibiae without extensor bristle but with subapical ones, hind meta- 

 tarsi darkened and not setulose;, mesonotal pubescence short; eyes 

 distinctly separated above the antennae 33. 



33. Hind tibiae with a rather strong apical spur 34. 



Apex of the hind tibiae simple; pubescence of dorsum blackish; veins 



dark gilvipes Loew 



34. Hairs of the thorax and of the calypteres whitish, some weak erect 



dorsocentrals on the disk of the mesonotum 35. 



Hairs of the thorax and calypteres blackish, no erect dorsocentrals on 

 the disk of the thorax; anterior cross-vein beyond the middle of the 

 discal cell 37. 



35. Anterior cross-vein at the middle of the discal cell; scutellum with four 



bristles; veins strong; one strong preapical extensor bristle on the 



hind tibiae, femora largely blackish Jemoralis Melander 



Anterior cross-vein at three-fifths the length of the discal cell, veins 

 weak; scutellum with two bristles; preapical extensor bristle of the 

 hind tibiae weak, legs mostly luteous 36. 



36. Hairs of the thorax fine but dense; face broader above and below and 



opaque gray pollinose, front poUinose; legs luteous facialis, n. sp. 



Hairs of the thorax sparse; face black, narrower below, the front black; 

 abdomen shining, nearly bare, pygidium very large; hind femora 

 blackish diversipes, n. sp. 



37. Apical spines of the hind tibiae stout, hind femora usually not blackened; 



first posterior cell widest before its end xantkopoda Williston 



Spines at the end of the hind tibiae rot unusually stout, hind femora dark 



on the distal half; third and fourth veins parallel 



[septentrionalis Melander) 38. 



38. Face linear, eyes subcontiguous beneath the antennae; palpi black 



septentrionalis Melander 

 Face narrow, white pollinose, the eyes distinctly separated; palpi yellow 



var. mexicana, n. var. 



39. Hind tibiae with a single extensor bristle near the middle; front very 



narrowly V-shaped; veins blackish and strong inermis, n. sp. 



Hind tibiae with two extensor bristles; front narrowly V-shaped; veins 

 slender 40. 



40. Antennae black, the third joint lanceolate; hairs of the body black and 



numerous, six acrostichals; sides of the fifth segment of the abdomen 



with many short scale-like setulae; tibial spur short nigricans, n. sp. 



Antennae yellow, the third joint short; hairs of the body pale and very 

 sparse, two acrostichals; tibial spvir long tenera, n. sp. 



