250 Annals Entomological Society oj America [Vol. XV, 



but above and near the eyes, grayish pubescent. The face is con- 

 siderably produced downwards and forwards; in profile moderately 

 concave from the antennal base to the prominent oral margin. Antenna; 

 reddish yellow, third joint longer than broad, its lower end more pointed, 

 not large, arista brownish, slightly noticeably pubescent. Vertical 

 triangle and a narrow V on the occiput behind the ocelli, grayish yellow 

 (sub-golden) pollinose, the ocellar triangle shining brown. Pile of the 

 head: A few pale hairs on the cheeks, posterior orbits with long 

 pale pile below, and short black pile arranged in definite rows above. 

 Thorax reddish brown, the sternum more blackish, but covered with 

 grayish pollen. Disc of the dorsum grayish pollinose, leaving four 

 stripes of a dark reddish brown or blackish, the median ones very 

 narrowly separated and expanded posteriorly to unite with the sub- 

 lateral bands, which are also entire; the opaque area is strictly confined 

 to the disc. A darker, thickly black pilose opaque stripe runs from 

 the postalar callosity to the suture; dorsum of thorax with short black 

 pile, the pleurae with longer, white pile. Scutellum brownish yellow, 

 with short black pile, with a few longer, bristle-like hairs apically. 

 Abdomen: First segment black, its anterior border yellow; second 

 segment pale yellow to slightly reddish yellow, with a median longi- 

 tudinal black stripe narrowly separated from the anterior margin, and 

 often joined to the black posterior margin or slightly separated from 

 it (the mark is ! shaped, without the dot below) ; hind border narrowly 

 black and sides of segment, except anteriorly, black; third segment 

 similar, darker colored, but the median stripe entire and the lateral 

 margins usually entirely blackish; fourth segment similar, but the 

 lateral margins m.ore brownish. Hypopygium yellowish red. Pile 

 of abdomen fine, whitish, except on the apical half of segments two and 

 three, where it is black. Legs reddish brown ; tarsi all brown or blackish, 

 except that the first three joints are yellow apically; hind femora 

 darker on apical quarter ; hind tibiae darker, with a pale median band ; 

 anterior four tibia? sometimes darker apically. Wings slightly yellowish 

 tinged, stigma pale luteous. Squamae clear white, with white pile. 

 Halteres slightly yellowish. In somewhat teneral specimens taken 

 in early May the abdominal markings are more brownish, and in fully 

 mature specimens the abdomen may be more reddish, and is always 

 wholly shining. The thorax may be slightly darker or paler than 

 described. 



Female. Averages .5 mm. smaller than the male. Face a little 

 more deeply excavated; front shining ferruginous with a very narrowly 

 interrupted whitish pollinose band below the middle; stripe on the 

 cheeks only a little darker than facial color or concolorous; median 

 abdominal stripe broader, complete on second, third and fourth seg- 

 ments; transverse bands broader and successively narrower apically; 

 fifth segment yellowish ferruginous with the narrow hind border blackish 

 and the lateral margins ferruginous or brownish. The general color is 

 more ferruginous than in the male. 



B. perplexa is evidently widely distributed, but it is 

 impossible to state its distribution owing to its confusion with 



