80 DIPTERA OP NORTH AMERICA. [PART III. 



upon the gibbosity, is darker, more brown ; upon the cheeks, with 

 the exception of the ferruginous-yellow border of the eyes, 

 chocolate-brown ; the two black ridges, bordering the middle of 

 the face, are present, as in P. undata, but even more distinctly 

 marked and descending lower. The first two joints of the 

 antennae are pale ferruginous-yellow; the third joint dark-brown; 

 the arista ferruginous-yellow at the basis, whitish towards the 

 tip; the second antennal joint is not quite as long as in the pre- 

 ceding species, chiefly because it is but very little less drawn 

 out forwards above than below; the last joint is at least by one 

 half shorter than the second, rounded oval, ending in a blunt 

 point ; the arista is inserted on the middle of its length, on the 

 outside, near the upper margin ; of its two basal joints the second 

 has four times the length of the very short first joint. The palpi 

 are slender, filiform, tinged with brown, like the proboscis. The 

 thoracic dorsum shows three deep black stripes ; the middle one 

 is very broad, begins at the anterior margin and ends some 

 distance before the scutellum ; the lateral stripes are abbreviated 

 anteriorly and posteriorly ; the portion of them behind the suture 

 is larger than that in front of it. The greater part of the pleurae, 

 a spot on each side at the posterior margin of the scutellum, 

 as well as the metathorax, dark-brown. On the abdomen, the 

 anterior part and the middle line of the first segment are pitch- 

 black and somewhat shining; on each of the following three seg- 

 ments is a triangular spot, of the same coloring, the basis of which 

 is directed anteriorly, and which occupies the whole breadth of 

 the segment. The upper part of the abdomen has delicate 

 transverse grooves, the under side on the contrary is strongly 

 grooved in a longitudinal direction, opaque velvet-black, with a 

 narrow, ochre-yellow middle line ; the projecting male organ of 

 copulation is of a shining reddish-brown. The feet are light 

 ferruginous, with yellow hairs ; the femora, to the exclusion of 

 the tip and tibiae, with the exception of the basis and of the ex- 

 treme tip, are chestnut-brown. The second longitudinal vein of 

 the wings is hardly perceptibly broken and without any vestige 

 of a stump; the wings in general are comparatively shorter than 

 in P. undata, darker and more evenly earth-brown ; a very 

 delicate streak near the posterior border of the first longitudinal 

 vein, not far from the origin of the second vein, the whole alula 

 and two streaks near the posterior margin, the position of which 



