148 THOMAS SAY FOUNDATION 



brissai which are at the oral margin; arista plumose 

 as usual a little over half its length. Palpi black; 

 proboscis very short; bucca one-third the eyeheight; 

 back of head with irregular black hairs above except 

 the outside row, below with some pale beard. Outer 

 vertical bristles present. 



Thorax heavily gray pollinose with the usual 

 3 to 5 black stripes ; ant acr unusually strong, 2 pairs ; 

 prsc rather small and slender ; ps dc 3 ; scutellum with 

 2 marginals; 1 subapical of good size and no apical. 



Abdomen with the usual cliangeable tessellation ; 

 the median dark line indistinct; in profile, the seg- 

 ments become successively deeper so that with the 

 flat hypopygium the shape of the abdomen is quite 

 unusual, being large and truncate behind. The first 

 and second segments have only lateral bristles, the 

 third with an interrupted row, the fourth with a row 

 diminishing on the sides, about 14 in all. First seg- 

 ment of hypopygium broad and bulky, usually black 

 with red apical margin, sometimes almost wholly red, 

 pollinose with erect hairs, some of which near the hind 

 margin are occasionally large enough to be regarded 

 as a row of bristles. In profile this hind margin is 

 nearly parallel with that of the fourth abdominal seg- 

 ment. Second red with rather abundant black hair, 

 short and more massive than in some species. For- 

 ceps peculiarly small, entirely yellow, the free part 

 suddenly narrowed from the attached part and al- 

 most perfectly straight, with a minute hook on the 

 front side at the tip; in profile not at all divergent. 

 Accessory plate yellow and stout, standing away 

 from the forceps at a considerable distance. Poster- 

 ior clasper yellow-white almost to tip, then excised in 

 semicircular form, leaving a slender apical hook; at 

 the beginning of the excision is a long hair; anterior 

 clasper in the form of a large, rounded yellow lobe, 

 concave behind, standing up beside the penis, at its 

 inner hind edge suddenly prolonged into a long slen- 

 der semicircular hook. Basal segment of the penis 

 strikingly slender; the apical segment from behind is 



