252 A. L. MELANDER. 



tiguous in both sexes. Thorax large, hunchbacked, abdomen long, 

 small at tip. Hind femora long, incrassate, with setulse beneath. 

 Wings generally spotted, second vein bowed towards the costa, third 

 vein simple, discal cell present, with two veins at its tip; anal cell 

 as long as the second basal, nearly truncate at its tip, anal angle 

 rectangular. 



Wings unspotted, or marked with only one spot 2. 



Wings with a black spot beyond the apex of the first vein and another at the 

 apex of the second vein ; marginal cell at tip of first vein twice as 

 wide as the submarginal cell at that point simplex Walker. 



2. Legs partly or wholly yellowish 3. 



Legs wholly black, thorax marked with a white polliifose humeral sjwt, and 



with a similar one in front of the scutellum ; stigma brownish. 



albouotatus Loew. 



3. Wings marked with a brown stigmal spot 4. 



Wings with a pale gray stigmal spot, femora wholly yellow. 



hyalinus Coquillett. 

 Wings unspotted, knob of halteres and the entire body black. 



pii$$i litis Loew. 



4. Marginal cell at apex of first vein twice as wide as the submarginal cell at the 



same point ; knob of halteres whitish 5. 



Marginal cell not widened 6. 



5. Thorax wholly yellowish rufus Loew. 



Thorax marked with three black vittae, or wholly blackish. 



thoracictis Say. 



(j. Knob of halteres black debiiis Coquillett. 



Knob of halteres brown qiiadraiij^tllaris Wheeler et Melander. 



Syueclies albonotatiis Loew. 



Cent., ii, 18. 



Black, opaque, thorax marked with white pollinose shoulder-spots and one 

 before the scutellum. Abdomen with fuscous pollen. Legs black, shining, tarsi 

 piceous, black towards apex. Wrings dark cinereous, veins black, stigma subob- 

 solete, pale fuscous. 3.5 mm. 



District of Columbia (Osten Sacken). 



Syiieclies hyalinus Coquillett. 

 Proc. Nat. Mus., 1895, p. 437. 



Opaque, black, base of the abdomen yellowish; antennae and knob of halteres 



" During daytime these flies rest on the under side of leaves, etc., in the shadiest 

 parts of the woods. Toward evening they fly about in the more open places and 

 capture minute Diptera. Holding their prey between the legs, and their body 

 being in a vertical position, they slowly fly toward the nearest bush, and, with- 

 out alighting, most dexterously manage to take hold of the edge of a leaf with 

 the claws of a front leg. Thus vertically suspended by a single leg, the fly uses 

 its five free legs for manipulating the gnat. Within ten seconds it has sucked 

 out its prey, then drops the same and flies away." 



