252 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



taiu distance, more distinctly attenuated, the dilatation being removed 

 farther toward the middle; the slender distal half is more elongated. 



Venation like that of Systoechus, but the relation between the cross- 

 vein at the base of the second posterior cell to that at the base of the 

 third is like 1 to 2 or 3 here, while it is like 1 to 5 or 6 in SystoecJius ; 

 this causes the proximal end of the third posterior cell to be less long 

 and pointed in Anastcechus, and renders the discal cell a little broader ; 

 the usual enlargement of the costa at the base, besides the usual pile, 

 bears a fringe of bristles. 



General outline of the body more elongated thau in Systcechus ; the 

 hairs on the end of the body longer, tuft-like. 



This genus answers Dr. Loew's first and smaller division of Systoechus 

 (Neue Beitr., iii, 35). The structural differences are of an importance 

 which not only justifies but requires the formation of a new genus. 



Anastcechus means "separated", in contradistinction from Systoechus, 

 "belonging together ". 



Anastcechus baebatus n. sp., $ 9. — Densely clothed with grayish- 

 yellow pile, mixed with some black pile at the end of the abdomen (espe- 

 cially in the male) ; beard white, with some black hairs above ; wings 

 grayish-hyaline, more or less brownish at the base. Length 5-7°^°^ (exclu- 

 sive of the length of the pile). 



Ground-color of the body grayish-black, densely clothed with long 

 pale grayish-yellow pile (much less yellow than that of Systoechus vul- 

 garis). Head with a dense beard of white pile, slightly yellowish round 

 the base of the antennse; above it, on the front, a tuft of long black 

 hairs, descending on each side along the eyes to about the middle of the 

 inner orbit in the male, much less in the female. Antennae black. 

 Chest with white pile. On the abdomen, besides the prevailing yellow- 

 ish pile, darker hairs are visible in rows, on the posterior margins of 

 the segments; they are black, and especially visible on the last two or 

 three segments, so that in most of the male specimens they impart a 

 blackish tinge to the pile around the tip of the abdomen ; the extent and 

 number of these black hairs is, howev^er, very variable, and in most 

 female specimens they disappear altogether. Knob of halteres yellow. 

 Femora, except the tips, black, but densely clothed with white scales ; 

 tip of femora, tibise, and tarsi reddish-yellow ; the usual spines of the 

 same color ; end of tarsi brown ; in the female, the yellow on the femora 

 is more extended. Wings grayish-hyaline, with a more or less extended 

 shade of brown at base, which is almost obsolete in the female ; costa 

 at the root with short yellowish- white and longer black pile, the latter 

 forming a kind of comb; wing- veins black, those at the root and near 

 the costa often pale brownish. 



jjab. — Cheyenne, Wyo., where I found it commonly on the 21st 

 of August, 1876. Five males and as many females ; the latter smaller. 

 Besides these, I have three specimens from the Twin Lakes, Colorado 

 (9,300 feet altitude, collected by Lieut. W. L. Carpenter), which I cannot 

 distinguish from the others, although they measure 10°^°^. 



