50 NORTH AMERICAN DIPTERA 



91. Wings with vein R: present 92 



Wings with vein R- lacking 95 



92. Rs at end of Rs, in alignment with the other elements of the cord; 



r-ni obliterated by the long fusion of veins R4+5 and M,+2; tropical. 



(Gonomyaria) Teucholabis: Paratropesa Schiner 



R; its length or more beyond the fork of Rs, R2+3+4 subequal to or 

 longer than R2; r-m distinct 93 



93. Wings with Rs long and straight, exceeding the distal section of 



M1+2; tuberculate pits on cephalic portion of prsescutum; trochanters 

 elongate; arctic and subarctic. (Rhabdomastix). 



Rhabdomastix: Sacandaga Alexander 

 Wings with Rs shorter, less than the distal section of M,+2; tubercu- 

 late pits removed from cephalic margin of prsescutum; ti'ochanters 

 short. ( Erioptera ) 94 



94. Wings with veins R3 and R4 strongly diverging, cell R3 having a 



Gonomyia-like shape Erioptera: Gonempeda Alexander 



Wings with veins Rs and Ri more generally parallel, cell R3 having 

 the more normal Erioptera-shape, but shorter. 



Erioptera: Empeda Osten Sacken 



95. Wings with Sc long, Sci extending to near opposite or beyond mid- 



length of Rs; m-cu at or beyond fork of M. (Eriopteraria, Rhab- 

 domastix ) 96 



Wings with Sc short, not extending to beyond midlength of Rs; if 

 Sc is relatively long (Ptilostena), m-cu lies more than its own 

 length before the fork of M. (Gonomyaria, Gonomyia) 97 



96. Antennae of male longer than body; chiefly tropical 



Rhabdomastix: Rhabdomastix Skuse 

 Antennae of male scarcely attaining wing-ioot; chiefly temperate. 



Rhabdomastix: Sacandaga Alexander 



97. Wings with m-cu more than its own length before form of M. 



Gonomyia: Ptilostena Bergroth 

 Wings with m-cu at or very close to fork of M (40) 98 



98. Wings with cell R3 very small, at margin subequal in extent to cell 



R.>; antennal verticils long and conspicuous. 



Gonomyia: Lipophleps Bergroth 

 Wings with cell R3 larger, at margin considerably exceeding in extent 

 cell R.; antennal verticils not conspicuously elongated. 



Gonomyia: Gonomyia Meigen 



99. Wings with distinct macrotrichia in outer cells 100 



Wings with the outer cells glabrous 103 



100. Wings with Rs shortened, its union with R2+3+4 forming an angle, so 



cell Ri is nearly equilateral in outline; chiefly tropical. (Eriop- 

 teraria) Cryptolabis Osten Sacken 



Wings with Rs long, normal in position, cell Ri elongate 101 



101. Size very small (wing, 3 mm. or less); Rs ending in cell R3, this cell 



thus being sessile, without element R-+3+4; temperate. (Eriop- 

 teraria) Dasymolophilus Goetghebuer 



Size larger (wing over 4 mm.); Rs ending in cell R4, cell R3 being 

 petiolate by the presence of a distinct element R;+3.4 102 



