154 ERNEST A. BACK. 



28. Abdomen with thick recumbent pile above; very thickly pilose 



species, in typical species the pile forming dense tufts on 

 the sides of the abdominal segments (not so in P. cirrhatus) 



(PI. X, fig. 8) Pycnopogon. 



Less pilose species (PI. X, figs. 4 and 5) Heteropogon. 



29. Front noticeably more widened above (PI. V, fig. 7); middle tibiae 



without two terminal inwardly directed spines (PI. II, 



fig. 4) 30. 



Front not widened above; middle tibia? with two terminal in- 

 wardly directed spines (PI. II, fig. 5) 31. 



30. Front unusually widened above and much excavated; bristles of 



thoracic dorsum when well developed two or three on each 

 side, one before the transverse suture, the other one or 

 two on the posterior callosity; third antennal segment 



rather elongate (PI. X, fig. 7) Sticliopogon. 



Front not unusually widened above; bristles on the lateral margins 

 and posterior callosities of thoracic dorsum and on the 

 scutellar margin numerous and well developed; third an- 

 tennal segment short and broad; species much resembling 

 Stenopogon in general appearance (PI. VII, fig. 3). 



Willistoniua. 



31. Large elongate reddish species, with deep brown wings (PI. VI, 



fig. 2) Callinicus. 



Smaller species with cylindrical abdomen; black, with bright 

 golden opaque pruinose markings on thorax and abdomen, 

 legs mostly yellow, wings nearly hyaline (PI. VI, fig. 6). 



Ghrysoceria. 



32. Face bare with bristles on the oral margin, in profile straight or 



concave, the oral margin most prominent 33. 



Face convex below, the oral margin not prominent, more or less 

 covered with hair 34. 



33. Fourth posterior cell closed a considerable distance before the 



margin of the wing (PI. IX, fig. 5) Deromyia. 



Fourth posterior cell open or closed in the margin (PI. VII, fig. 4). 



Saropogon. 



34. Third segment of antennas more or less dilated, the style very 



short, the thoracic dorsum when viewed from before with 

 four longitudinal rows of long bristles, one each on either 

 side of the median stripe and on the lateral margins (PI. 



X, fig. 1) Lestomyia. 



Third segment of antennas slender, elongate 35" 



:;."). Abdomen finely punctate; the third segment of antennae quite 

 elongate, notched on the upper side near the middle and 

 there bearing a forward directed spine (PI. Ill, fig. 6). 



Taracticus. 

 Abdomen smooth, not finely punctate 36. 



