OSTEN SACKEN ON WESTERN DIPTERA. 245 



hairs, mixed with black ones, on the anterior margin of the thorax, op- 

 posite the occiput; the edge of the scutellum with a yellowish- white 

 tomentum and a row of stiff black bristles. Ground -color of the abdo- 

 men black; first segment on each side with a tuft of yellowish-white 

 pile and a sparse fringe of them along the hind margin ; second seg- 

 ment black, with a faint streak of microscopic fulvous tomentum in the 

 middle ; the following segments are densely clothed with a recumbent, 

 short, yellowish tomentum, more whitish on the hind margins of the 

 segments; in the middle of each segment, the tomentum, being less 

 dense, leaves a dark spot, which, in connection with similar spots on 

 the next segments, forms an ill-defined longitudinal dark stripe; rows 

 of black erect pile on each segment above the yellow pubescence; the 

 black pile is more dense on the sides and at the end of the body; the 

 sides of the two last segments are clothed with whitish, scale-like pile; 

 the same whitish scales form subtriangular spots on the hind corners of 

 the third and fourth segments, connected with the fringes of whitish 

 hairs on the hind margins of the segments. Femora black; four front 

 tibiae and tarsi dark brown ; the front femora are sparsely beset on 

 the anterior side with whitish-gray scales. Halteres yellow 3 the knob 

 with a brown spot. Wings grayish-hyaline ; their root, the costal cells, 

 the two basal cells, and the proximal ends of the anal and axillary cells 

 pale reddish-brown ; a transverse darker brown cloud on the small 

 cross-vein, and the bifurcation of the second and third veins ; another 

 darker cloud, coalescent with the brown of the base of the wings, lies 

 between the origin of the praefurca and the cross- vein at the base of the 

 fourth posterior cell. The stump of a vein on the anterior branch of the 

 third vein is small, sometimes obsolete ; that on the curvature of the 

 second vein is moderately long ; there is none in the second posterior 

 cell. Length 10-ll mm . 



Hab. — Dallas, Texas (Boll). Three specimens. The description was 

 drawn from a well-preserved female. 



As mentioned in the introductory paragraph to this genus, the larva 

 of this species lives in the nest of a Mud- wasp (Pelopceus ?), and this 

 alone induced me to describe it. I did not dare to identify it with 

 Anthrax bastardi Macq., and still less with Anthrax eostata Say. 



Triodites nov. gen. 



Belongs in the number of genera which forms the passage between 

 the Anthracina and Bombylina. It has the appearance of an elongated 

 Anthrax; the antennae are distant at the base, and resemble those of 

 that genus. But the eyes of the male are contiguous for a short dis- 

 tance, high up, on the vertex, and the bifurcation of the second and third 

 veins takes place long before the small cross- vein, the preefurca being 

 very short. Triodites, like Oncodocera and other genera of the same 

 group, has, in the male, a very large frontal triangle, and, in the female 

 a correspondingly large frontal space. 



