1917] New Species of Colorado Syrphidce 231 



parallel. Third segment slightly contracted (viewed dorsally) ; legs 

 short, rather stout, hind femora short, decidedly thickened, moderately 

 pilose with long golden hairs; hind tibiae thickened, slightly arcuate, 

 with a few stout spines at apex; metatarsi thickened. Marginal cell 

 of wing open, third longitudinal vein gently curved, anterior cross-vein 

 oblique, beyond middle of the discal cell. The fourth section of the 

 fourth longitudinal vein zigzag with two stump veins projecting outward. 



Type of genus Microxylota Robii. 



Microxylota robii n. sp. 



Length, iS.o to 7 mm., face black with moderately thick, pale, 

 yellowish pile, front narrow above, black, with silvery pollinose and 

 sericeous pile; cheeks shining black; vertex shining black, black pile; 

 eyes contiguous for a short distance, sparsely pilose; occiput shining 

 black, extending broadly baclavards; antennae fuscus, pollinose, third 

 joint rhomboid, somewhat pointed at tip; arista dorsal, bare, brownish. 

 Dorsum of thorax shining, metallic greenish black, w4th two pollinose 

 tapering stripes running from anterior portion to about middle of thorax, 

 yellowish pilose; scutellum same color as thorax, thinned at the edge. 

 Pile sparse, short, yellowish; abdomen approximately one-third longer 

 than thorax; shining metallic greenish black, only four visible segments 

 from above, sides nearly parallel, slightly tapering from anterior portion 

 of second segment to the tip of abdomen; segments two, three and four 

 with latro-medial, opaque, crescentic, whitish, pollinose depressions. 

 Second segment broad, third slightly contracted; fourth rounding at tip, 

 pile short, yellowish; legs strong, black, hind femora extremely thickened, 

 shining black, with short, yellowish pile, tibiae gradually dilated from 

 base to apex, arcuate, base reddish brown, tarsi reddish brown; hind 

 metatarsi incrassated at base, gradually tapering to apex. Wings 

 sub-hyaline, stigma brown. The apical bounding vein of the first 

 posterior cell zigzag with two stumps of a vein projecting forward. 



Two specimens, males, collected by C. S. Mead, Fort 

 Collins, Colorado, June and August, 1915. 



