272 ERNEST A. BACK. 



9 . — Like the male, but the face is a little more bare upon the sides, 

 the pile throughout somewhat shorter, the dorsum more grayish 

 pruinose, in front leaving two slender median dark stripes, the light 

 pile of the abdomen is less abundant and extends on the sides to the 

 fourth segment, and the black pile very short; the posterior angles of 

 segments 2-4 white pruinose; the pile of the femora is more obscure, 

 the silvery pile of the anterior, and the black disk of the middle tarsi 

 wanting." 



Type. — University of Kansas. " Two males and two fe- 

 males." One of the male co-types marked "type" is at the 

 'M. C. Z. and is in poor condition. 



Middle tarsi* of male without brushes of black bristles. 



Cyrtopog - oii aurifex. 



Cyrtopogon aurifex Osten Sacken, West. Dipt., 301, 1877. 

 % 9- — Length %, 8.2 mm.; ?, 9-10 mm.— "J 1 . — Abdomen narrow, 

 tapering, black, polished, with some bluish reflections on the first seg- 

 ment and very distinct purplish toward the tip before the hypopygium; 

 first segment on the sides with tufts of black pile anteriorly and white 

 pile posteriorly; the hind part of the second and the greatest part of 

 the third and fourth segments are occupied each by a conspicuous 

 broad fringe of long, erect, yellowish-fulvous fur, with narrow base 

 spaces between these fringes. The three following segments are cov- 

 ered with short, dense, erect, deep black hairs, forming a brush, es- 

 pecially conspicuous on the sides, and longer posteriorly before the 

 hypopygium; the purplish-black, polished ground color is almost cov- 

 ered up by this pile; hypopygium black, polished, with but little pile 

 Face and front with brownish-gray bloom; face with whitish pile above 

 and black pile below; occiput with white pile below and black pile 

 above and on the vertex; third antennal segment red; the style black. 

 Thorax black, brownish pruinose, especially about the humeri; a brown 

 geminate stripe, with a paler, grayish-yellow dividing line in the middle. 

 Femora black; front tibiae red at base, black on their distal half; the 

 other tibiae red, broadly black at tip; tarsi black, the base of the first 

 segment and the extreme root of the following segments red; first three 

 segments of the front tarsi with some white pile on the upper side. 

 Wings brownish hyaline; fourth posterior cell hardly coarctate. 



" J ■ — Legs like those of the male; only the red on the tarsi occupies 

 more space and the front tarsi have no silvery pile; the hairs on the 

 face are more scarce and whitish; the abdomen comparatively narrow, 

 polished black; segments 2-5 each with a moderately broad cross-band 

 of yellowish- white bloom near the posterior margin; segments 2-4 are 



* Under this come several species, the males of which have never 

 been taken. 



