338 ERNEST A. BACK 



Snow has kindly loaned me the type and I find that Dr. Wil- 

 liston is quite right, and that there is little to add to his 

 original generic description found above. The tarsal segments 

 are rather stouter than those of Stenopogon, and in addition 

 to the already mentioned preapical bristles there is a single 

 bristle on the upper anterior side of the middle femora near 

 the middle. 



I have named this genus in honor of Dr. Williston, to whom 

 belongs the credit for its discovery, and whose description I 

 have compared with the type species and found entirely sat- 

 isfactory. 



Willistonlna bilineatus (PI. IV, fig. 5 ; PI. VII, fig. 3). 



f Habropogon bilineatus Williston, Trans. Am. Ent. Soc, XI, II, 

 1884; PI. 1, fig. 8. 



" 9- — Length 15 mm., of wings 9 mm. — -Black, gray pruinose; mystax 

 white; dorsum of thorax yellowish-gray, with two slender opaque black 

 stripes; abdominal segments 1-5 with red borders; under side of all 

 the femora and base of tibiae red. 



" Face and mystax white, the former opaque; front a little yellowish- 

 gray, the few short bristles black. Antenna; and proboscis both short, 

 black. Dorsum of thorax gray with a yellowish or brownish cast; the 

 ground color of humeri, posterior callosities and scutellum appears to 

 be yellowish-red; in the middle two slender narrowly separated, but 

 very distinct, opaque black stripes, obsolete on posterior part; bristles 

 wholly black. The ground color of the pleura; apparently in large 

 part reddish, but concealed beneath a dense, very light colored bloom, 

 which also covers the coxa;. Abdomen black, rather thinly yellowish- 

 gray pruinose, the terminal segments more polished, the sides and 

 posterior margins of the first four segments and the sides of the fifth 

 red; the pile is very short; fore and middle coxa; thickly clothed with 

 white pile. Legs black; the under side of all the femora broadly red, 

 the base of the posterior tibiae and the four anterior tibiae, except their 

 tips, red, or yellowish-red. Wings nearly hyaline, veins black." 



Type. — University of Kansas. A single female specimen. 



Habitat. — Northern California (O. T. Baron). 



There is almost nothing to add to the above description. 

 The bristles on the dorsum of thorax are arranged as follows: 

 a row extending from the lateral margin before the transverse 

 suture upward and backward over the base of the wing, three 

 on each posterior callosity, two on each side of the scutellar 

 margin, and two rows of shorter bristles on the posterior por- 



