Williston.] ^'^^ [May 19, 



"W. — Face carinate see XIII. 



"VVW. — Face tubcrculate, or rounded, not carinate. 



X. — Face of male less tuberculate than in female, body uniformly 

 black, without markings. 

 Y. — Hind tibiae of male with a strong projecting spine in middle. 



Teuchocnemis. 



YY. — Hind tibiae of male without such spine "^Pterallastes. 



XX. — Face alike in both sexes, abdomen in male at least (except Malloia) 

 not unifoi'm. 

 Z, — Hind coxa5 with spur, duller in the female, hind femora with tri- 

 angular protuberance, hind tibitie with terminal spur (^T abdomen 

 mostly red, $ nearly black) Polydonta. 



PoLYDONTA CURVIPES (Wied.), Aus. Zwei. ii, 149, 3. O. S. "West. 

 Dipt., 338. New England ! California. The probability is that the species 

 somewhat doubtfully referred to this by Ostcn Sacken, 1. c, is the same. 



ZZ. — Hind legs without such spurs or protuberances. 



a. — Third joint of antenna^ broad, face concave below the anten- 

 nae (thorax not vittate, thickly pilose) abdomen without 

 bands Mallota. 



MATiLOTA Sackeni, sp. nov. 



Mallota posticata O. Sacken, West. Dipt., 338. 



(5*. Differs from M. (?) posticata of the Eastern States in a dark brown 

 spot on the wing, in the marginal cell being closed in the border, and 

 in the eyes of the male not being contiguous, otherwise quite like the 

 Eastern species. 



Frontal triangle and face gray with yellow pile, broad fiicial stripe and 

 cheeks deep black, shining ; antennae black, third joint more or less 

 brownish. Dorsum of thorax and pleurae with long dense yellow pile, 

 scutellum yellow, similarly pilose, abdomen deep shining black, nearly 

 bare, legs deep black, with black pile, middle and posterior tarsi brownish- 

 red, posterior femora verj^ much thickened. Wings hyaline with a large 

 brown spot, reaching from the origin of the third vein to the small cross- 

 vein, the second longitudinal enters the costa at tip of the fii'st, not at 

 some distance beyond, as in the specimens I have of the Eastern species. 

 Long. corp. 14mm. Washington Territory. Two specimens. 



aa. — Third joint of antennae ovate, face excavated or not below the an- 

 tennae, thorax, or at least abdomen, with markings Helophilus. 



Helophiltjs latiproxs Lw., Cent, iv, 73. Wyo. ! Northern States, 

 Nebraska, California. 



Helophilus mexicanus Macq. (//. liolygrammus Lw. Cent. x. 55. See 

 also O. Sacken, Catalogue, Errata.) Ai)parently a very common species. 

 I have seventeen specimens from Washington Territory and California. 



Helophilus, sp. A small species from Wyoming, apparently unde- 

 scribed. 



