TABLE OF THE FAMILIES. 3 



Antennae shorter than the thorax, the joints broadly and closely united, 

 without marked constriction, and never hairy or pilose; legs strong, 

 hind pair more or less dilated ; body thick-set, abdomen ovate; wings 

 broad, bare, the anterior veins stouter, the posterior weak. Black- 

 flies, Buffalo-gnats SIMVLIIDJG. 



12. Wings ovate, distally with ten longitudinal veins and without cross- 



veins; veins strongly hairy; tibiae without terminal spurs; small, 

 lepidopter-like flies, the wings when at rest folded roof-shaped. 



PSYCHODIMC. 



Wings with cross-veins near the middle 13 



13. Wings hairy, fringed on the hind margin ; mosquitoes. CULICID^E. 

 Wings bare ; the second vein arises near the middle of the wing. 



DJXIID^E. 



14. Third joint of the antennae complex; basal cells of wing long. . 15 

 Antennae composed of three simple joints, the third not annulated or 



segmentated, with or without a dorsal arista or terminal style or 

 arista 18 



15. Empodia undeveloped or bristle-like ; antennae elongate, composed of 



four or five joints, without differentiated style or arista; vertex and 

 front hollowed out transversely between the eyes ; eyes of male 



never contiguous . . 25 



Empodia developed pulvilliform ; third antennal joint more or less dis- 

 tinctly segmentated or annulated ; body not bristly. . . 16 



16. Tegulse rather large; third longitudinal vein furcate; five posterior 



cells always present; the costal vein encompasses the whole margin 

 of the wing; proboscis of the female adapted for piercing; third joint 

 of the antennae with from three to eight annuli, never with style or 



bristle. Horseflies . TABANID^;. 



Tegulae small or rudimentary ; mostly flower-flies. . ' . . 17 



17. Tibiae wholly without spurs ; longitudinal veins of the wings usually 



crowded anteriorly,* the posterior ones often weak ; the costal vein 

 does not reach beyond the tip of the wing; antennas long or short, 

 with or without a terminal or dorsal arista or terminal style. 



STBATIOMYIDJE. 



The middle tibiae, at least, with distinct spurs ; the costal vein encom- 

 passes the entire wing; third longitudinal vein always furcate and 

 five posterior cells always present. . . ... LEPTIIWE. 



18. Antennae apparently single-jointed, with a long bristle; wings with sev- 



eral stout veins anteriorly, and other weaker ones apparently con- 

 nected with them; femora flattened, the hind legs long; antennae 

 situated near the mouth ; small, quick-running, hunchbacked flies. 



PHOKII^E. 

 Not such flies. . . -. . . . . ^ . . 19 



* If very large flies from Central America, compare ACANTHOMKKID.*. 



