OSTEN SACKEN ON WESTERN DIPTERA. 279 



Entoin. Monatsschr., 1857, p. 33, tab. i, f. 1), with the following differ- 

 ences: — 1. The first posterior cell is divided in two (nearly equal) parts by 

 a cross- vein placed between the end of the discal and the proximal end of 

 the second submarginal cell (the same character distinguishes the two 

 North American Opsebius described by Mr. Loew in the Centuries) ; 2. 

 The third and fourth posterior cells have their proximal ends nearly on 

 the same line ; in other words, the insertion of the intercalary vein is 

 coincident with the cross- vein at the base of the fourth posterior cell ; 3.' 

 The fifth vein, runs straight to the margin, and the sixth is incurved 

 toward it a short distance from the margin. The costa is distinctly 

 thickened between the ends of the first and the third veins, and a little 

 beyond the latter. The wing is distinctly tinged with brownish, except 

 at the base and the tip, which are subhyaline. 



Body of a uniform brownish black, slightly metallescent on the 

 thorax. Thorax densely clothed with brownish-yellow erect pile, not 

 dense enough, however, to conceal the shining surface under it. On 

 the abdomen, the same pile is more dense on the second segment ; the 

 pile on the two intermediate segments is more blackish, except along 

 the posterior margins, where it is yellowish; the fifth has a shorter and 

 more appressed whitish-yellow pubescence, interspersed with longer pile ; 

 the last segment is black, shining, transversely rugose. Legs brownish- 

 yellow; femora slightly tinged with brownish; coxae, except the extreme 

 tip, brown. Halteres with a yellowish- white knob ; tegulae semitrans- 

 parent, colorless. Eyes pubescent; antennae (broken). 



Hdb. — Vancouver Island (G. R. Crotch). Two specimens. 



Opsebius paucus n. sp.— -Very like 0. diligens, but smaller, 4-5 mm long; 

 sixth vein interrupted before the nearest cross-vein, and thus the anal 

 cell open ; the branches of the fourth vein do not quite reach the mar- 

 gin. Antennae yellowish-brown at base; distal portion of the last joint 

 and arista nearly black; pubescence of the eyes long and dense. 

 Thorax with very dense, soft, erect, grayish-yellow pile ; the greenish- 

 black, shining ground-color but little visible under it. Abdomen brown- 

 ish-black, moderately shining, densely clothed with brownish-yellow 

 erect pile; the penultimate segment and the hind margin of the pre- 

 ceding one are clothed with recumbent yellowish-white pile. Wings 

 slightly tinged with brownish, much less than in 0. diligens, but more 

 uniformly, as the paler color of the tip is not apparent. The rest as in 

 0. diligens. 



Hab. — California (G. R. Crotch). One specimen. 



Oncodes melampus Loew, Centur., x, 17. — California. I have a 

 specimen (brought by G. R. Crotch) which I doubtfully refer here. The 

 tibiae are brown, not black; the borders of the tegulae very pale brown- 

 ish ; the wing- veins are very pale, except those near the costa, which are 

 brownish. 



Oncodes incultus n. sp. — Brownish-black; humeral callosities 

 brownish-yellow ; antescutellar callosities yellowish-brown ; posterior 



