68 NORTH AMERICAN DIPTERA. 



entiated into a style or arista; (decomposed of three simple joints 

 (sometimes apparently two}, with or without a differentiated, one to 

 three-jointed, style or arista. Second vein of the wing never furcate, 

 the third often; discal cell almost always present. 



14. Antennae composed of two or three simple joints, the distal one 



not annulated nor segmentated, usually with a one to three- 

 jointed terminal or dorsal arista or terminal style (cl) , . 18 

 Antennae of the structure of (a), (b) , or (c). . . . 15 



15. Empodia undeveloped or bristle-like; antennae elongate, the fla- 



gellum composed of two or three joints, without apparent style; 

 front concave between the eyes in both sexes. ... 25 

 Empodia developed pulvilliform; flagellum of antennae with nu- 

 merous, distinct joints, or forming the complex, so-called third 

 joint, with or without a differentiated style or bristle; body not 

 bristly. .......... 16 



B. Antenna; composed of more than five joints, or the third-joint 

 complex, four to eight segmented, inclusive of style or arista zchen 

 present: 



16. Squamae rather large; third longitudinal vein furcate; five poste- 



rior cells always present; the costal vein encompasses the wing; 

 flagellum composed of from four to eight segments, never with 

 style or arista; males holoptic; proboscis of female adapted for 

 piercing. Horseflies, gadflies, greenheaded flies. 



Tabanidge, 176 



Squamae small or vestigial; for the most part flower flies; males 

 usually holoptic. . . . . . . . . 17 



17. Tibiae without spurs; wing veins not crowded anteriorly; third 



antennal joint composed of seven annuli with a terminal slender 

 style or arista; two submarginal, five posterior cells always pres- 

 ent, the fourth closed. Very large, robust, southern flies. 



Acanthomeridae, 173 



Tibiae almost invariably without spurs; longitudinal veins of the 

 wings usually more or less crowded anteriorly, the posterior 

 ones often weak; the costal vein does not reach beyond the tip 

 of the wing; scutellum often with spines; third vein almost al- 

 ways furcate; four or five posterior cells, the fourth rarely or 

 never closed; antennae long or short (b) , (c). 



Stratiomyidse, 164 



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



