66 S. W. AVILLISTON, M. D. 



and prominently a little above the middle of the face. Antennae black; the first 

 two joints with short white hair, the third joint scarcely as long as the first. 

 Front narrowed above, with white hair, a few black bristles on each side below, 

 the ocelli with tvro conspicuous black bristles. Oecipilo-orbital bristles black, the 

 beard abundant, silky-white; bristles on the palpi black. Thorax strongly con- 

 vex behind, clothed with short black hairs and black bristles, in color reddish 

 brow n, with yellowish gray pollen, varying in different reflections, the two median 

 dark brown stripes distinct, separated by a narrower pollinose stripe, in front of 

 the seutellum in certain lights a slender T)rown triangle, the ground color of the 

 central stripe and the humeri often red. Seutellum thickly dusted, with black 

 bristles on its border. Pleurae thickly gray pollinose, with whitish pile, except a 

 little black on the mesopleurae. Abdomen slender, brownish black, a little shin- 

 ing; first segment wholly whitish pollinose; second to the fifth segments thickly 

 whitish pollinose on the sides, extending inwards on the posterior angles but not 

 quite meeting in the middle ; between the black and the gray on each side there 

 is a semi-lunar spot of brown ; sixth and seventh segments wholly silvery-white 

 pollinose, except a slender brown longitudinal spot on the dorsum of the sixth; 

 hypopygium large, black, with black pile. Legs with whit6 hairs and black 

 macrochaetse, the hind tibiae on the inner sides and their metatarsi with short 

 orange-red pile; in color the femora on the under side, the tips of the tibiae, and 

 the tarsi are black, elsewhere deep red; in structure the hind tibiae are rather 

 slender for the basal two-thirds then dilated and on the outer side distinctly an- 

 gulated, just below the knee on the outer side there are two conspicuous bristles 

 bent downwards, and on the front side on the distal fourth with a brush of short 

 black pile. Wings nearly hyaline, a little yellowish behind ; the furcation of the 

 third vein beyond the distal end of the discal cell, the anterior cross-vein near 

 the outer fourth ; costal vein distinctly thickened and curved outward beyond the 

 tip of the auxiliary vein. 



5'. Two rubbed females show the structure of the head and thorax as in the 

 male, the hind tibiae and the wings normal, not dilated. 



Ilah. — Arizona. 



Erax jiibatiis n. sp. 



%. — Length 18-19 mm. Black. Facial gibbosity large and protuberant. Face 

 deep brown, covered with moderately thick grayish pollen, especially near the 

 eyes; mystax composed of black and white hairs, long, abundant, spread out 

 helmet-shaped. Antennae black, the first two joints with black and white hair, 

 the third joint small. Front clothed with rather long black hair. Beard abun- 

 dant, silky-white; occipito-orbital bristles slender, mostly black. Dorsum of 

 thorax strongly convex, deep brown with grayish yellow pollen, along the middle 

 a moderately broad row of long, thick pile or hair, beginning in front and reach- 

 ing to near the seutellum ; on the posterior part, however, diffuse and longer; in 

 front the sides of the dorsum have only diffuse sparse short pile. The bristles are 

 short and rather thin ; on the seutellum with long hair, its border with thin 

 bristly hairs. Pleurae thinly pollinose, and with sparse, long, pile. Abdomen 

 black, clothed on the upper side with long silky, not abundant, mostly white pile, 

 the third, fourth and fifth segments with a posterior, rather narrow gray pollinose 

 border, on the sides of the segments broader and more brownish ; sixth and seventh 

 segments wholly silvery-white; hypopygium large, black, with black pile; venter 

 with tufts of long silky-white pile. Legs black, with silky-white pile; tibiae and 



