68 THOMAS SAY FOUXDATIOI-: 



Easily recognized in botli sexes by a patch of 

 appressed, silky yellow or whitish hair, almost like 

 tomeritiim, on the outer third of tlie front side of the 

 middle fenmr. 



Male. Front .247 the width of the head; (aver- 

 ave of live, — .225, .236, .256, .257, .263) ; median 

 stripe about as wide as the side, the latter with pale 

 yellow sheen which extends smoothly down the para- 

 facial; a row of four or five small bristles on lower 

 part of parafacial; frontal row of nine bristles, the 

 lower strongly diverging; antennae black, third joint 

 less than double the length of the second, but reach- 

 ing nearly to the mouth; arista long, plumose for 

 about half its length; vibrissa? large, at oral margin; 

 palpi black, not swollen; proboscis ordinary, black; 

 bucca over one-fourth the eyeheight; inner verticals 

 long, outer about half as long; back of head with 

 about 3 series of black hairs, the inner irregular; the 

 pale beard sparse. 



Thorax gray, when viewed from behind with 3 

 blackish stripes and a short narrow one each side; 3 

 ps dc ; no acrostichals except a small prescutellar pair : 

 scutellum with 2 long marginal pairs, 1 small subapi- 

 cal pair, and small erect crossed apical pair; 3 stpl. 



Abdomen black, tessellated, not tapering; sec- 

 ond segment with a median marginal pair of bristles 

 and a lateral; third segment with a median, a subme- 

 dian, and tw o or three laterals ; fourth with a continu- 

 ous row of about 22. 



Both segments of the hypopygium shining black, 

 with erect hairs which become almost bristle-like on 

 the hind margin of the first; genitalia as figured, shin- 

 ing black except at bases of the parts; fifth ventral 

 segment in the form of a pair of black lobes bearing 

 a stiff brush of spines, longer on the inner edge. 



Legs black, middle femora without comb of 

 spines below ; hind tibia? with a few long, slender hairs 

 on inner front side. 



