222 DIPTERA OP NOJRi'fi AMERICA. [PART IV. 



basis of the flagellum not longer than broad, somewhat more 

 elongated and slender towards the tip ; verticils comparatively 

 short. Thorax grayish-brown ; an obsolete pale brown double 

 stripe above ; halteres pale at the basis ; knob slightly infuscated ; 

 feet dark tawny, slightly infuscated at the tips of the femora and 

 of the tarsi; coxse and basis of the femora pale. Abdomen 

 brownish ; forceps paler. Wings faintly tinged with brownish ; 

 stigma very slightly darker ; the second submarginal cell only a 

 trifle longer than the first posterior ; the second posterior is five 

 or six times shorter than its petiole ; the petiole of the first sub- 

 marginal cell is distinctly shorter than the great cross-vein; 

 marginal cross-vein very faint, about the middle of the distance 

 between the tip of the first longitudinal vein and the inner end 

 of the first submarginal cell ; great cross-vein about the middle 

 of the discal cell ; seventh longitudinal vein straight, except the 

 extreme tip, which is a little curved. 



Eab. Washington, D. C, in April. I had eight male speci- 

 mens when I first described this species. A number of them 

 were swarming round a spring, in the woods. One of the speci- 

 mens has a faint indication of an adventitious cross-vein in the 

 middle of the first basal cell. The black pits on the humeri are 

 well marked, but the double dot in the front of the mesonotum 

 is obsolete. 



18. L«. ultima 0. S. % and 9 • — Grisea, thorace vittis quatuor fuscis ; 

 alis hyalinis, irnmaculatis ; antennis fuscis, articulis flagelli basalibus 

 quatuor coalescentibus, incrassatis ; cellula submarginalis secunda 

 prima posteriori parum longior ; vena longitudinalis septima recta. 



Gray, thorax with, four brown stripes ; wings hyaline, immaculate ; an- 

 tennae brown ; the four basal joints of the flagellum are coalescent, in- 

 crassated ; second submarginal cell but little longer than the first 

 posterior; seventh longitudinal vein straight. Long. corp. 0.28 — 0.33. 



Syn. Limnophila ultima 0. Sacken, Proc. Ac. Nat. Sc. Phil. 1859, p. 238. 



Head and thorax of a pure gray ; antennas and palpi brown ; 

 the antennae, if bent backwards, would hardly reach the basis of 

 the wings ; the four first joints of the flagellum are short and 

 almost coalescent, forming an elongated almost conical body, 

 which is stouter than the remainder of the antenna ; the following 

 joints are elongated, subcylindrical ; joints rather short. The 

 thorax has four distinctly-marked brown stripes ; the intermedi- 



