BITING MIDGES — WIRTH AND BLANTON 269 



radial cell; anal cell with two distal pale spots; mesonotum with promi- 

 nent pattern lanei Ortiz (p. 374) 



60 (54). Cell M2 with one pale spot distal to level of base of mediocubital fork, 



not counting any spot lying immediately anterior to base of fork . 61 



Cell M2 with two (or one with at least part of a second) pale spots 



lying distal to level of mediocubital fork 77 



61. Cell R5 with a U-shaped pale spot (sometimes reduced to two separate, 



round spots) enclosing a small, round, dark spot just behind second 

 radial cell; crossvein r-m usually dark; mesonotum uniformly dark 



brown acotylus Lutz (p. 367) 



Cell R5 without pale area enclosing a round, dark spot behind second 

 radial cell; crossvein r-m pale 62 



62. Distal pale spot in cell Mj not attaining wing margin 63 



Distal pale spot in cell Mi broadly attaining wing margin; distal pale 



spot in cell R5 large, filling apex of cell; wing very hairy; third palpal 

 segment bulbous; one pale spot at apex of anal cell 



magnipalpis Wirth and Blanton (p. 360) 



63. Anal cell with two distal pale spots 64 



Anal cell with one distal pale spot 67 



64. Crossvein r-m with pale spot small and lying entirely on distal side of 



vein, not reaching anterior wing margin; cell R5 with one small 

 transverse pale spot distal to the poststigmatic pale spots. 



mirsae Ortiz (p. 446) 



Crossvein r-m lying entirely within a pale spot which reaches anterior 



wing margin 65 



65. Halter knob dark (only at base in tetrathyrus) ; no pale spots lying 



next to anterior sides of veins Mi and M2 near bases 66 



Halter entirely pale; small, elongate pale spots present adjoining 

 anterior sides of veins Mi and M2 near bases; cell R5 with an oblique 

 double poststigmatic pale spot and a single large round pale spot 

 past it in middle of cell; hind femur with subapical ring and hind 

 tibia with broad apex pale . . poikilonotus Macfie (part) (p. 337) 



66. Cell Rj with four, small, round pale spots arranged in a rhomboid in 



midregion; r-m crossvein pale; apices of hind femur and tibia dark. 



tetrathyris, new species (p. 409) 



Cell Rs with three small, round, pale spots arranged in a triangle in 

 midregion; r-m crossvein dark; hind femur with subapical ring and 

 hind tibia with apex pale lyrinotatus Wirth and Blanton (p. 391) 

 67 (63). Mesonotum with prominent pattern of punctiform brown dots; 

 three small round, equidistant pale spots in a triangle in cell Rs; 

 halter knob dark at base; two spermathecae; eye bare; antennal 

 segments in a continuous series, sensoria on segments in, vii-x. 



ginesi Ortiz (p. 450) 



Mesonotum with prominent pattern of large patches or without promi- 

 nent pattern 68 



68. Smaller species (wing 0.65 mm. long); distal pale spot in cell Rs large 

 and rounded, nearly filling cell from wing margin to vein Mi; macro- 

 trichia sparse, only a few in apices of cells R5, Mi and M2; antennal 

 segment xi shorter than x 69 



Larger species (wing 0.8-1.4 mm. long); distal pale spot in cell Rj 

 usually transverse, not nearly filling breadth of cell; macrotrichia 

 more numerous, present at least on distal half of wing; antennal 

 segment xi equal to or longer than x 71 



475684 0-59-3 



