North American Diptera. 21 



at its base with the discal cell ; the marginal vein encompasses the 

 whole wing; some or all the tibiae with spurs. 



Third joint of the antennae annulate, never with differentiated 

 style or bristle ; tegulae rather large. . Tabanid^: 



Third joint of antennas simple, with a simple, or thickened styli- 

 form, bristle ; tegulaj rudimentary. LEPTiDiE 



TABANID^. 



Species never very small, often among the largest in the order; 

 never thickly pilose ; in life the eyes usually brilliantly colored and 

 marked. Head short, broad, eyes large. Antennae porrect, the 

 third joint composed of from three to eight annuli or segments. 

 Thorax not very convex, scutellum without spines on its border. 

 Abdomen broad, moderately elongate or short, never slender or con- 

 stricted. Legs moderately stout, the front and middle tibiae some- 

 times dilated, the middle tibiae always with spurs. Veins of the 

 wings distinct; first posterior cell (and fourth in exotic species) 

 rarely closed. 



Early stages passed in the water or earth ; larvaj carnivorous, with 

 a distinct head ; pupae free. The females are blood-sucking, usually 

 found in the neighborhood of pastures, in sunny open parts of woods, 

 during the hot sun-shiny days of summer. The males are much 

 more rarely met with, and will be found usually in sweepings of 

 meadaw lands, on flowers, etc. 



1. Hind tibiaj with spurs at their tips, sometimes small. (Pan- 



goninae.) 2 



Hind tibia^ without spurs ; ocelli absent. (Tabaninae.) . 5 



2. Third joint of the antenna? composed of eight annuli, the first of 



which is only a little longer than the following ones. 3 



Third joint composed of five or fewer segments, the first of which 



is much longer than the following ; ocelli present. 4 



■i. Front of female narrow, without denuded callus ; ocelli rarely 



absent. Pangonia 



Front of female broad, with a large, broad, denuded callus; ocelli 



present. ...... Apatolestes 



4. Second joint of the antennae about half as long as the first ; wings 



hyaline or with small spots ; eyes in life with numerous small 



dote. SiLVios 



