BITING MIDGES — WIRTH AND BLANTON 263 



4. Hind femur dark to apex; apices of veins M3+4 and Cui usually pale . 5 

 Hind femur with subapical yellow band; apices of veins M3+4 and Cui 



dark; third palpal segment slender, without pit; mesonotum yellow 

 in middle with dark brown sublateral vittae; wing 1.3 mm. long. 



verecundus Macfie (p. 278) 



5. Midknee broadly yellow at the joint; mesonotum dark gray in middle, 



nearly unicolorous blackish; third palpal segment slender, without 

 pit; wing 1.5 mm. long .... heliconiae Fox and Hoffman (p. 274) 

 Midknee black with narrow pale rings on each side; mesonotum yellow 

 in middle with dark brown sublateral vittae; third palpal segment 

 swollen with a shallow, subdivided pit; wing 1.2 mm. long. 



hylas Macfie (p. 276) 



6 (3). Cell Ml with two pale spots distal to the double spot straddling vein 



M2; palpal pit with regular margins present; halter knob pale or 



dark 7 



Cell Ml with only one pale spot distal to the double spot straddling 



vein M2; palpal pit irregular or absent; halter knob brown .... 8 



7. Small black spot present on vein R4+5 near end of second radial cell; 



halter knob dark; larger species (wing 1.2 mm. long), foxi Ortiz (p. 283) 



No small black spot on vein R4+5 near end of second radial cell; halter 



knob usually pale; smaller species (wing 1.0 mm. long). 



diabolicus Hoffman (p. 280) 



8 (6). Vein R4+5 blackened into adjacent distal pale area up to a point where 



vein turns abruptly forward to meet the costa; mesonotum with 

 prominent pattern; third palpal segment with definite, irregular 



sensory pit insignis Lutz (p. 285) 



Vein R4+5 not blackened into adjacent distal pale area; mesonotum 

 uniformly grayish brown pruinose; third palpal segment without 

 sensory pit trinidadensis Hoffman (p. 287) 



9 (2). Very small species, wing 0.64-0.69 mm. long; costa short, extending 



only 0.53-0.57 of distance to wing tip; second radial cell short; 

 mesonotum bluish black with faint sublateral black vittae .... 10 



Larger species, wing 0.72-1.66 mm. long; costa longer, reaching 0.58-0.79 

 of distance to wing tip; second radial cell usually long; mesonotum 

 yellowish to brown (or if blackish there are gray patches present and 



the legs are 4ark) 11 



10. Second radial cell p^ale only on extreme distal end; wing pattern very 

 faint; legs pale except for dark knee spots; pit of third palpal segment 

 faint or absent; spermathecae oval and subequal. 



pusillus Lutz (part) (p. 292) 



Second radial cell on distal half; wing pattern prominent; legs brown 

 with pale bands; palpal pit deep; spermathecae subspherical and very 



unequal pusilloides Wirth and Blanton (p. 290) 



11 (9). Legs stout, fore and hind femora greatly swollen, subapical pale rings 

 present on all femora; mesonotum dull, tawny, yellowish brown; 

 distal sensory tufts absent on antennal segments xi-xv 12 



Legs slender, femora slender, yellow with dark knees or dark with pale 

 knees, never with subapical pale rings; mesonotum if yellow then 

 subshining; distal sensory tufts present on antennal segments xi- 

 XV 13 



