72 NORTH AMERICAN DIFFER A. 



25. LONCHOPTERIM;. 



Small (2-4 mm.) slender, brownish or yellowish flies. An- 

 tennae short, porrect; third joint simple, circular in shape, 

 with a terminal bristle. Ocelli present. Scutellum with two 

 bristles. Legs long, bristly ; pulvilli very small ; empodia 

 wanting. Wings lancet-like, pointed ; the three basal cells of 

 moderate size and of nearly equal length ; fourth longitudinal 

 vein furcate and united with the fifth near the base ; first 

 longitudinal vein short, second and third not furcate ; the 

 anterior cross-vein lies near the base of the wing, in front of 

 the middle of the second basal cell and is oblique in position. 



There is but one genus in this family, Lonchoptera, the 

 members of which are found, often in abundance, in the grass 

 or upon stones along the margins of shady brooks. The lar- 

 vae are flat with long bristles on the first, second and last seg- 

 ments ; posterior spiracles broadly separated on the last 

 segment, short and tubular. Head not differentiated, the 

 body composed of ten segments, the last one apparently com- 

 posed of two. Pupae enclosed in a puparium, orthorrhaphous. 



26. EMPIDID.E. 



Small to moderately large, elongated, predaceous flies. 

 Head small, more or less spherical, not closely applied to the 

 thorax. Males holoptic or dichoptic, the front never exca- 

 vated. Antennae porrect, approximated at the base, composed 

 of three simple joints, the first two of which are often small ; 

 third joint variable in shape, with or without a terminal arista 

 or style. Face without mystax. Proboscis short or long, 

 projecting forward, downward or backward. Ocelli present. 

 Abdomen composed of from five to seven segments, male gen- 

 italia prominent and of complicated and variable structure ; 

 ovipositor projecting, pointed. Tegulae small. Legs often 

 with peculiar structural characters the coxae or femora elon- 

 gated, the femora thickened and with spines below, the meta- 



