DASYPOOONINAB 



ROBBER FLIES OF THE WORLD 



93 



interrupted by pale brownish yellow pollen along the 

 suture and the humerus, and a posteromedial triangle 

 of similar pale pollen extends in front of the lateral, 

 blackish stripe. The sides of the mesonotum are also 

 widely pale brownish yellow pollinose as well as the 

 mesopleuron and upper sternopleuron. Elsewhere on 

 the pleuron the pollen is distinctly greyish white and 

 quite dense. Pile and the numerous, long but quite 

 slender, bristly hairs or slender bristles of the meta- 

 pleuron pale yellow. Bristles of the mesonotum and 

 scutellum distinctly reddish yellow, except for the single 

 pair of black posterior dorsocentral bristles. Mesono- 

 tal setae black broadly over the middle of the mesono- 

 tum, becoming yellow laterally and across the anterior 

 margin of the mesonotum. Scutellar setae black. 

 Halteres large and brownish yellow. 



Legs : The basal half of all the femora pale yellow, 

 the color obliquely but not sharply delimited and the 

 black of the outer portion extends dorsally a little closer 

 to the base on the anterior pair, and both black and 

 yellow color is densely overlaid by white pollen. Basal 

 fourth or less of middle and hind tibiae and basal three- 

 fourths of anterior tibia also light yellow. All of the 

 tarsi quite dark brown. Pile of the tibiae and tarsi 

 quite dense, appressed, setate and yellow. Claws black 

 with only the extreme base dark brown. 



Wings : The wings are hyaline ; veins light brown. 



Abdomen: The abdomen is brownish black, more 

 nearly black on the basal half of the second tergite, also 

 nearly black on the basal two-thirds of each tergite from 

 the third to the sixth and also on the basal half of the 

 first tergite, in the middle only. These black areas are 

 only found across the center of the basal part of the 

 tergites, the side margins become extensively pale 

 greyish yellow pollinose. Posterior margins of the 

 third and remaining tergites rather widely yellowish 

 brown in underlying ground color. This color is less 

 extensive on the first two tergites. In the females the 

 seventh and eighth tergites are visible but are short and 

 entirely creamy yellow ; ultimate segment is black. Most 

 of the setae on the black areas are brownish black and 

 flat appressed. Setae of the posterior margins a little 

 longer, appressed and yellow. Lateral pile and bristles 

 pale yellow, including those of the terminalia. Male 

 terminalia dark brown with pale pollen. 



Type: Male, Camamina, Bolivia, July 1921-22, W. 

 M. Mann; allotype, female, and 3 male and 12 female 

 paratypes, all with the same data. Types in the U.S. 

 National Museum ; alternate paratypes in the collection 

 of the author. 



Genus Perasis Hermann 



Figures 86, 442, 877, 886, 1666, 1674, 1998, 1999 



Perasis Hermann, Berliner Ent. Zeitschr., vol. 50, p. 37, 1905. 

 Type of genus: Perasis sareptana Hermann, 1905, by 

 monotypy. 



These are medium size flies of greatly reduced pile 

 and characterized further by the open marginal cell, 



nonrecurrent second vein, the closed first posterior cell, 

 crossing of the upper and lower end veins of the second 

 basal cell, the copious coarse pile of the face and the 

 prominent, spoon-shaped, medially cleft microsegment 

 of the antenna. Scutellum without bristles. Length 

 12 mm. 



Head, lateral aspect: The head is of medium length, 

 the face distinct in profile, though not prominent. It 

 has a low elevation beginning at the antenna and con- 

 tinuing to near the epistoma, where it is rounded and 

 retreating. The eye is distinctly longer below, strongly 

 convex on its ventral profile, and gently convex an- 

 teriorly. The occiput towards the middle of the head 

 grows thick and tumid on the ventral half but is exca- 

 vated and reduced on the upper half; it is pollinose, 

 with slender bristles beginning at the lower third, where 

 there are 2; at the middle there begins a row which 

 contains 12 increasingly stout bristles, ending near the 

 middle of the postvertex. The proboscis is rather small 

 but strongly swollen at the base, cylindrical, blunt at 

 the apex, which carries a few minute hairs chiefly di- 

 rected downward; there are also a few hairs below at 

 the base. The proboscis directed obliquely downward, 

 or if forward it does not extend beyond the face. Pal- 

 pus quite slender, the basal segment small, the end 

 segment cylindrical, longer, with 2 conspicuous, long, 

 slender bristles at the apex and a few other hairs ven- 

 trally. The antenna is attached at the upper third of 

 the head and nearly as long as the head ; antenna com- 

 paratively slender. The first segment is longer than 

 the second, the first two segments as long as the third. 

 The third segment is very little wider or higher than 

 the basal segments, stout even at the base and slightly 

 narrowed at the apex ; it bears an oblique, robust micro- 

 segment which is longer below, deeply notched in the 

 middle and carries at the bottom of the notch a spine. 

 Head, anterior aspect: The face is one-fourth the 

 head width, slightly wider below, uniformly pubescent 

 and with abundant, obliquely directed, coarse, bristly 

 pile over nearly the whole surface. This pile becomes 

 a little longer along the epistomal margin and contains 

 medially above the margin a patch of 7 or 8 weak 

 bristles. Anterior eye facets greatly enlarged. Front 

 not at all widened; it is not wider than the upper face 

 including the vertex; the vertex is deeply excavated, 

 with a high ocellar protuberance with slanting sides, 2 

 pairs of slender, divergent bristles, and 2 or 3 additional 

 pairs, all located between the ocelli. The front is short 

 and together with the vertex pollinose; the orbital mar- 

 gin of the front bears a row of coarse hairs ; the anterior 

 ocellus greatly enlarged. 



Thorax : The thorax is elongate and low, uniformly 

 convex, densely appressed, setate, pile undifferentiated 

 and feebly shining; it bears pollen laterally and over 

 the whole pleuron. Mesontal complement of bristles 

 consists of 3 notopleuron, 2 to 4 supraalar, and no post- 

 alar or scutellar bristles. Scutellum thick, convex, 



