80 



NORTH AMERICAN DIPTERA 



Family Dixid^ 



Dixa species. 



Eather small, slender, nearly bare species occurring near running 

 water. 



Proboscis somewhat projecting; palpi four-segmented; antennas 

 long, the basal segments swollen, the flagellar segments hair-like and 

 poorly separated; ocelli absent; eyes round. Thorax strongly convex, 

 without transverse suture; metanotum arched; scutellum transverse. 

 Abdomen long and slender, composed of seven or eight segments, thick- 

 ened posteriorly in the male, pointed in the female. Legs long and 

 slender, the coxaj somewhat elongated; tibiae without terminal spurs. 

 Wings rather large; auxiliary vein present, ending in costa before the 

 middle of the wing; two complete basal cells. 



This family may be readily recognized by the wing venation. The 

 adults often dance in swarms at a height of a few inches to a few feet 

 above the surface of small streams in swampy or wooded areas and 

 occur also along the edges of ponds. 



The larvge are aquatic and resemble those of mosquitoes but the 

 thorax is not broadened. They are cylindrical, somewhat flattened be- 

 neath, and n-shaped. 



There are but two known genera, Ncodixa occurring only in New 

 Zealand, and Dixa, which is cosmopolitan. I present a key, adapted from 

 Edwards, to the genera and subgenera of the world. 



