70 S. W. WILLISTON, M. D. 



segment a little brownish; ovipositor black; hyyopygium large, black, with black 

 pile. Legs black, the tibife yellow, their tips and the tarsi reddish brown or 

 blackish. "Wings short, hyaline, the veins luteous, the furcation of the third vein 

 takes place a little beyond the end of discal cell ; anterior cross-vein a little beyond 

 the middle of the discal cell. 



Two specimens, Western Kansas (E. W. Guild, F. H, Snow). 



A single 9 specimen fiom N. Mexico (E. Keen) closely resembles 

 this, but belongs to a diflFerent species. The front is rather broader above ; 

 there is scarcely a trace of the dorsal stripes ; the abdomen is less thickly 

 pollinose, showing a pair of indistinct blackish spots on the 2-5 seg- 

 ments. The size is also less. 



Eras lateralis. 



Erax lateralis Macquart, Dipt. Exot. i, 2, 116, 21. 



.? Erax ambiguus Macquart, Dipt. Exot. 1 er. Suppl. 84, 34. 



? Asilus interruptus Macquart, Hist. Nat. Dipt. ], 310, 29. 



% , 9 • — Length 21-25 mm. First two joints of the antennae yellowish red, with 

 short black pile; third joint black, nearly as long as the first two togetlier, only 

 a little shorter than the bristle. Face densely covered with yellowish white pol- 

 len, the mystax not very abundant, leaving a bare space on the sides and above, 

 yellowish wliite; on its upi>er part with a number of more porrect black bristles. 

 Front a little more yellowish, without any black hairs or bristles. Oecipito-orbital 

 bristles black, beard abundant, wliite. Dorsum of thorax clad with short black 

 hairs, longer toward the scutellum ; on the sides, beginning from in front of the 

 wing, with four moderately long black macrochsetee, on the post-alar callosities as 

 many more, and on the posterior part of the dorsum with two short rows of weaker 

 ones. Sides of the dorsum and the pleurae densely yellowish white pollinose, on 

 the middle of the dorsum there are two distinct blackish brown stripes, contiguous 

 posteriorly, and separated by a linear interval from a lateral less distinct stripe. 

 Pile of pleurae and coxae white, except a little black pile on the mesopleurae. 

 Scutellum yellowish pollinose and white pilose above; along its margin with a 

 row of not very strong black macrochaetse. Abdomen opaque black, and with 

 very short black hairs, except as follows : first segment wholly thickly wliitish 

 pollinose and with white pile, except narrowly in the middle, on the lateral mar- 

 gins with a few black bristles ; second and third segments, except on their middle 

 portion, with loose white pile, slender in the 9; when seen from behind their 

 lateral margins and a broad posterior cross-band, broadly interrupted, densely 

 white pollinose ; when seen from atjove often there is only a large black spot in the 

 middle and a smaller one on each side in front; in the male the fourth segment 

 with narrow lateral margins, a little dilated at the hind angles of the fourth and 

 continued across as a narrow smooth hind band on the fiftli, likewise white pollin- 

 ose; in the female there are slender crossbands on the hind margins of the fourth 

 and fifth segments in addition to the lateral margins, in the fourth the band is 

 interrupted, in the fifth entire, or nearly so ; in the male the sixth and seventh 

 segments are densely whitish yellowish pollinose, except a small black triangle in 

 the middle above; in the female the yellowish white pollinose sixth segment has 

 a large black triangle, the base of which lies on the slender yellow hind margin, 

 and its tip on the front margin, the seventh segment similar, but the triangle 

 larger. Hypopygium unusually small, reddish, with white pile, except a small 



