SYNOPSIS OF NORTH AMERICAN SYRPHID^. 21 



NAUSIGASTER. 



Xausigaster Williston, Trans. Amer. Ent. Soc, xi, 33, 1885. 



Moderate sized, nearly bare species, black in ground-color, but thickly 

 pollinose, with shining, numerous small black punotulate spots. Head 

 spheroidal, broader than the thorax. Eyes bare, contiguous in the male. 

 Front narrowed above, evenly arched to the autennie, which are situated 

 a little above the middle of the head in profile. Face narrowed below, 

 concave on upper part below the antennae; the tubercle near the middle 

 large, obtuse, below it much receding to the oral margin, resembling in 

 structure the species of Paragus^ but more concave above the tubercle and 

 more receding below it, the tubercle being higher up. Cheeks narrow. 

 First and second joints of the antennae extremely short, so that the third 

 joint appears sessile, the latter thickened, large, subquadrate, as broad as 

 long, the angles rounded, and narrower on the basal portion ; aristasmall, 

 bare, very short, not as long as the third antennal joint, remote from 

 the base, situated upon the anterior rounded angle near the eud of joint. 

 Scutellum small, convex, but thinned along its margin. Abdomen very 

 convex above, beyond the middle being in cross-section two-thirds of a 

 circle; first segment short; second segment moderately long; third 

 segment much shorter than the second in the middle, on the sides about 

 as long, the incisure in front forming a deep stricture, less evident be- 

 hind; fourth segment very large, as long as the three preceding together, 

 forming half of an ellipsoid, flattened on one side, the strongly convex 

 end extending beyond the anal opening, and wholly concealing the fol- 

 lowing segments. The sides of the abdomen are directed downward 

 and inward, inclosing toward the outer part of the venter a deep cavity, 

 shallower on the second and third segments; at the posterior part of 

 this cavity, and concealed by the posterior rim, is the anal ojiening look- 

 ing obliquely forward; back of the anus on the rim on each side is a 

 small obtuse membranous flap or process. Hypoi)ygium small, wholly 

 concealed. Legs as in Paragus — rather short and moderately strong, the 

 hind metatarsi thickened. Wings more like those of Syritta than of 

 Paragus. The first longitudinal vein joins the costa a little before the tip 

 of second vein, and then by a curve at the tip, so that the vein runs 

 parallel to the costa for some distance. The anterior cross- vein is near 

 the basal third of discal cell, and the third vein beyond is gently bisin- 

 uate. The last section of the fourth vein is sinuate like it is in Syritta, 

 but more deeply so, the vein terminating very near the costa, but form- 

 ing nearly a right angle at its juncture. 



Type of genus, K. punctulata Williston, N. America. 



Nausigaster punctulata. (Plate I, figs. 10, 10a.) 



Xausigaster pnuctulata Williston, Trans. Amer. Ent. Soc, xi, 34; pi. ii, fig. 15. 

 Habitat. — ISTew Mexico, California, j\Iexico ! 



9 . Length, 12°»™. Black, moderately shining, everywhere, except on 

 legs and venter, covered with whitish pollen, which, when not rubbed, 



