NORTH AMERICAN DIPTERA. 175 



53. — Discal cell wholly brown ; anal, axillary and fourth posterior cells also 



brown (j8. Tasta. 



Discal cell with the apex pure hyaline .3(!. perploxa. 



54. — Face, femora and tibiae partly or wholly reddish 55. 



Face wholly black fiO. 



55. — Brown of wings does not reach base of second subniarginal cell 56. 



Brown of wings reaches base of second subniarginal cell along the veins; 

 outline of the brown not distinct ; second vein strongly curved S-shaped 



before its apex 45. mira. 



56. — Front tibite provided with bristles 57. 



Front tibiae destitute of bristles; dorsum of thorax opaque, velvet-black; 



anal and axillary cells wholly brown 31. riilvoliirta. 



57, — Veins at bases of first and fourth posterior cells not bordered with subhya- 

 line; face greatly produced below; proboscis never projecting half its 



length beyond the oral margin 58. 



Veins at bases of first and fourth posterior cells distinctly bordered with 

 subhyaliue; face retreating below; proboscis projecting half its length 



beyond the oral margin 41. rex. 



58. — Brown of wings does not fill entire base of discal cell to small cross-vein ; 



length of bodyS — 11 mm 59. 



Brown of wings fills entire base of discal cell to small cross-vein ; length 



of body 5—9 mm .30. porplexa. 



59. — Anal cell wholly brown 69. lacuiiaris. 



Anal cell having nearly the apical third hyaline 29. syrtis. 



60. — Pile and tomentum of head and abdomen wholly black ; base of wings to 



tip of discal cell blackish ; the apex hyaline 23. atrata. 



Pile aud tomentum of head and abdomen partly white or yellowish 61. 



61. — Apex of wings beyond base of second subraarginal cell never distinctly 



hyaline and brown; either wholly hyaline or wholly smoky 62. 



Apex of wings beyond base of second submarginal cell distinctly hyaline 

 and brown ; three submarginal cells in each wing; second vein strongly 



curved S-shaped before its apex 2. jiierpciitiiia. 



62. — Wings destitute of a brown cloud at base of second submarginal cell 64. 



Wings with a brown cloud at base of second submarginal cell ; front tibiae 

 destitute of bristles ; no subhyaliue border to veins at bases of first and 



fourth posterior cells t)3. 



63. — First two antennal joints subequal in length, base of the third joint sub- 

 globular ; tomentum of occiput white 32. cantor. 



First antennal joint nearly twice as long as the second, base of the third 

 joint elongate-conical ; tomentum of occiput yellowish. ..40. <li!«par. 



64. — Front tibiae destitute of bristles 67. 



Front tibiae provided with bristles 65. 



65. — Veins at bases of first and fourth posterior cells not bordered with sub- 

 hyaline; tomentum of occiput white 66. 



Veins at bases of first and fourth posterior cells bordered with subhyaliue : 

 proboscis projecting half its length beyond the oral margin : tomentum 



of occiput yellowish 41. rox. 



66. — Face much produced below; tomentum of basal half of abdomen laru'ely 



yellow, pile of sides also yellowish 3(i. pcrplt'xa. 



Face not produced below; tomentum of bassil half of abdomen black ; pile 

 of sides also black 25. curtai. 



TRANS. AM. ENT. SOC. XIX. JUNE. 1SU2. 



