I 



282 DIPTERA OF NORTH AMERICA. [PART IV. 



long as the head and thorax taken together, the flagellum with 

 nearly cylindrical, elongated, densely pubescent joints, of nearly 

 equal length, except the last, which is shorter. The knob of the 

 halteres is distinctly infuscated ; the stigma, likewise, is slightly 

 brownish ; the vertex seems to be darker than in D. rivularis ; 

 the wings of the male are somewhat narrower, and the praefurca 

 a little longer ; the interval between its origin and the nearest 

 marginal cross-vein, in both specimens which I have before me, 

 is longer than the interval between the two cross-veins. 



I have two males in my possession, taken together with the 

 specimens of D. rivularis. At that time (compare Proc. Acad. 

 Nat. Sci. Pliilad, 1859, p. 250) I was uncertain whether they did 

 not belong to the latter species. I venture now to describe them 

 as distinct ; the antennae are of a length which is otherwise un- 

 usual in the genus. 



Gen. XXXIX. PUECTROM1TIA. 



Two submarginal cells ; four posterior cells; discal cell open; the sub- 

 costal cross-vein is a considerable distance before the origin of the second 

 longitudinal vein ; the marginal cross-vein is very near tbe tip of the first 

 longitudinal vein (Tab. II, fig. 18). Tibiae with exceedingly minute spurs 

 at the tip ; empodia small, but distinct. Eyes pubescent ; antennae 13- 

 jointed. The upper horny appendage of the forceps of the male is fiat, 

 rounded, with a serrate edge. 



A rather broad front separates the eyes above ; in well pre- 

 served dry specimens, it rises abruptly above the antenna? and is 

 rather convex, without showing any trace of a bump (having 

 neglected to describe it from a fresh specimen, I have abstained 

 from any statement about it in the generic character). Rostrum 

 short ; palpi short ; the first joint is the longest, the others stout, 

 short; the last is not much longer than it is broad. Antennae 

 13-jointed (I have counted the joints on fresh specimens) ; first 

 joint elongated, subcylindrical ; the joints of the flagellum, except 

 the first, which is subconical, are rounded, slightly elongated, 

 with short verticils ; they are clothed with a short pubescence, 

 which is more dense in the male ; if bent backwards, the antennae 

 would not reach the root of the wings. Collare w^ell developed, 

 with a short, neck-like prolongation towards the head ; the meta- 

 notum moderately gibbose above it ; thoracic suture well marked. 

 The feet are long (although much shorter than in Rhaphidolabis) ; 



