£10 DIPTERA OF NORTH AMERICA. [PART II. 



the pale, and, on account of its shortness and delicacy, almost im- 

 perceptible pubescence, quite a number of black bristles. Feet 

 black, the femora with a more coppery, the tibiae with a more 

 metallic-greenish tinge. Fore femora rather strongly thickened 

 towards the basis, on the under side with strong black bristles of 

 different length, on the front side only with an imperfect row of 

 short black bristles. Middle femora moderately thickened and 

 strongly curved, on the under side of the basis with two or three 

 not very long, on the apical half with a large number of long, 

 straight and erect bristle-like black hairs. Hind femora plain, of 

 middling stoutness, on the under side with bristle-like short hairs ; 

 on the upper side with two longer black bristles, of which the 

 larger is not far from its tip. Fore tibiae strong, with a large and 

 sharp thorn on the front side, not far from the basis ; elongated at 

 the tip into a large clumsy tooth ; the under side of the tibia, pro- 

 vided with bristles, has no distinct excision before this tooth. 

 Middle tibiae long, straight, a little stronger in the neighborhood 

 of the basis ; the first two thirds of their under and posterior side 

 are fringed with long curly black hairs, the end of the under and 

 front side, however, with long and stiff black bristles ; on the under 

 side, where these bristles begin, there is between them a somewhat 

 curved black thorn. Hind tibiae straight, on the under side with 

 short but very strong black bristles, one of which, being not far 

 from the tip, is remarkable for its greater length ; on the outside 

 of the tip of the tibiae a few shorter and one somewhat longer 

 curved bristle are inserted. Tarsi plain, their joints of decreasing 

 length ; the first joint of the fore and middle tarsi on the under 

 side with black bristles, which are of considerable length near the 

 basis of the tarsi, but decrease in length very rapidly so as to be 

 very short on the larger portion of the joint ; the under side of 

 the first joint of the hind tarsi is everywhere beset with short black 

 bristles. Halteres pale-yellowish, but the basis of the knob some- 

 what brownish. Wings hyaline ; almost the whole basal third 

 appears somewhat whitish when seen in a certain direction ; gray- 

 ish stripes along the second half of the second and third longitu- 

 dinal veins, likewise along the tip of the last segment of the fourth 

 and the greater portion of the fifth longitudinal vein ; there is 

 also a gray streak between the third and fourth longitudinal veins ; 

 upon the posterior transverse vein there is a blackish-gray double 

 spot, and upon the middle of the last segment of the fourth longi- 



