AMERICAN DIFTERA. 317 



few short hairs, the first joint over twice as long as the second, the third joint 

 twice as long as the first, glabrous, lanceolate, somewhat blunt in the female, 

 black, the arista two-thirds the length of the third joint; bristles of the occiput 

 in two rows. Mesonotum normally with brownish gray dust over a black 

 ground, sometimes the covering eflaced, when the thoracic disc is highly polished, 

 marked with four brown, conspicuous, rather broad vittse, the outer two abbrevi- 

 ated in front; the intervittal spaces with a few minute bristles, margin of the 

 notum with four macrochsetse, one on the humerus, one snpra-alar, one on the 

 post-alar ridge and one in front of this; scutellum with two marginal macrochse- 

 tfe; the humeri, pectus, post-alar ridge, margin of the scutellum, sides of the 

 metanotum and the pleurae largely yellowish, dusted with cinereous ; the ground 

 color of the pleurae darkened above the base of the four posterior coxae and in 

 front of the root of the wings; bristles of the pronotal collar slender, sparse, of 

 the metaplenral row about three in number. Abdomen shining, yellowish, with 

 an indistinctly limited median blackish stripe; the segments with a subapical 

 series of long slender black bristles, the hairs of the abdomen sparse and minute ; 

 hypopygium comparatively long, vertical, yellowish, not densely provided with 

 hair, nearly closed, but its parts visible, central filament slender, curved, ex- 

 posed, except near the tip, the middle lamellae erect, their posterior margin 

 inflected, the apical corner with a deep emargination ; the upper lamellae rela- 

 tively small, with dense, fine hairs; styles of the female reddish. Coxae yellow, 

 all provided with few black hairs on the front surface near the tip; trochanters 

 and tip of femora with the usual small black spots; legs yellow, except the more 

 or less brownish tarsi, rather slender, the hind femora not surpassing the abdo- 

 men and not longer than the tibiae; none of the metatarsi thickened, the front 

 ones as long as the next three joints, the hind ones somewhat shorter, the middle 

 metatarsi as long as the two succeeding joints; the last four tarsal joints with a 

 double series of spinose hairs ; legs clothed with short black hairs, longest distally 

 and conspicuous on the hind legs of the male ; trochanters simple ; the hind 

 femora of the male swollen on the outer third, provided with a subapical median 

 tubercle on the under side, which is tipped with a slender black spine curved 

 towards the end of the femur, on a line with this, but on the infero-exterior 

 edge, is a short fringe of black bristles, on the outer under edge, opposite the 

 fringe, is a scoop-shaped triangular dilatation of the femur, with a subapical 

 emargination on the hind edge; these processes articulate with structures near 

 the base of the tibia, the median spine of the femur corresponding with an elon- 

 gate blunt tubercle, into the emargination of the femoral scoop fits a small tooth 

 which is provided on the outer side with a small fringe of black bristles; the 

 apex of the hind femora provided with a series of bristles above, and narrowed 

 as in the angulate basal part of the tibia; legs of the female simple, not thick- 

 ened. Halteres pale yellow. Wings slender, long, hyaline, with a faint brown- 

 ish tinge, no stigmal spot present; the furcation of the third vein, which takes 

 place opposite the end of the marginal cell, the posterior branch ending beyond 

 the wing-tip; discal cell rather small, the proximal section of the vein bounding 

 it anteriorly one-fourth the length of the second section, no long costal bristles 

 present. 



Numerous specimeus of both sexes. Lawrence, Kansas (Dr. S. 



W. Williston). 



TRANS. AM. ENT. SOC, XXVIII. SEPTEMBEK, 1902. 



