DA8IP000NINAB 



ROBBER FLIES OF THE WORLD 



117 



Head, anterior aspect : The face cover is micropubes- 

 cent, apilose with a considerable number of long, 

 slender bristles occupying a low triangular area across 

 the face above the epistomal margin and extending 

 down along the sides of the subepistoma. The antenna 

 are attached at or just above the middle of the head in 

 profile, comparatively short, the first 2 segments nearly 

 equal in length, the second beadlike, considerably wider 

 and more robust than the first. The third segment is 

 widest in the middle, only slightly compressed laterally 

 and gently sloping to the base and apex, neither of 

 which are greatly narrowed ; the truncate apex bears a 

 rather stout, slightly attenuate microsegment, which is 

 a little more than one-third as long as the third seg- 

 ment and carries a minute apical spine. The front is 

 conspicuously divergent, with at the outer third, a shal- 

 low, longitudinal crease continued back on either side 

 of the ocellarium; sides of the front submarginally 

 with 4 stout, long bristles and several additional hairs. 

 Vertex moderately excavated, with gently sloping sides, 

 the ocellarium comparatively large and between the 

 ocelli with one rather stout and one rather slender 

 bristle, both long and with 3 pairs of additional fine, 

 short, stiff hairs. Anterior eye facets centrally en- 

 larged. 



Thorax : The thorax is pollinose, pile of mesonotum 

 scanty, suberect and bristly or setate. Acrostical 

 bristles consist of a narrow, poorly differentiated band 

 of 3 or 4 irregular rows. Dorsocentral bristles are 

 absent; humeral pile scanty, short and bristly, the 

 lateral margins with rather stout, quite long bristles: 

 2 notopleural in a diagonal row, 1 supraalar, 1 postalar, 

 and no scutellar bristles. Scutellum flat, pubescent, 

 transversely wrinkled with very shallow crease me- 

 dially at the base, deep creases laterally, the margin 

 with a few, fine, quite short, rather stiff hairs. Meta- 

 pleuron with 4 slender bristles in a vertical row and a 

 few, stiff hairs behind. Lateral metasternum without 

 pile; ventral metasternum chitinized with a few, fine, 

 long hairs; the postmetacoxal area membranous. Te- 

 gula pubescent only. Squama with a few fine hairs 

 medially, apparently in one row. 



Legs: The femora very slightly thickened through 

 the middle portion, especially on the anterior pair ; the 

 pile is fine, appressed and setate dorsally on the femora 

 and tibiae and these areas pollinose or pubescent. Ven- 

 tral pile rather abundant but fine, short, erect on the 

 femora only, the tibial ventral pile scanty, delicate, 

 bristlelike and suberect. Bristles well developed, 

 rather long, and, considering the size of the species, 

 rather stout. 



Wings : The marginal cell and all the posterior cells 

 widely open, the fourth is opened by two-thirds of the 

 maximum width; middle end vein of the second basal 

 cell rather long; anal cell closed with a short stalk. 

 Alula extremely narrow; ambient vein complete. 



Abdomen : The abdomen at the base is as wide as the 

 thorax, sometimes with parallel sides to the end of the 



fourth segment, or with the sides rolled and therefore 

 tapering and more slender. The pile is quite short, ap- 

 pressed and setate, slightly longer but still flat ap- 

 pressed laterally. Sides of first tergite with only stiff 

 hairs, Male with seven tergites, the seventh is one-half 

 as long as the sixth. Female with eight tergites, the 

 eighth nearly as long as the seventh ; the last two female 

 tergites with short, fine, erect pile. Male terminalia 

 comparatively short, rotate one-fourth to the left ; epan- 

 drium completely cleft and developed into large and 

 conspicuous superior forceps. Female terminalia with 

 8 pairs of long, slender, apically pointed, spoonlike 

 spines ; ventral plate extending will beyond the eighth 

 tergite and notched at apex, compressed, troughlike 

 and V-shaped; lower lateral process with weak bristles. 

 This subgenus has only one species. 



Genua Townsendia Williston 



Figubes 54, 514, 936, 945, 1665, 1693, 1989, 2018 



Townsendia Williston, Kansas Univ. Quart, vol. 4, p. 107, 1895. 

 Type of genus: Townsendia minuta Williston, 1S95, by 

 monotypy. 



Exceptionally minute flies characterized by the long 

 subglobular head from the lateral aspect, the im- 

 mensely enlarged anterior eye facets, short proboscis 

 and the strongly divergent front. These flies possess 

 all of the characters of the tribe. Only 4 posterior cells 

 present. Length 3.5 to 5 mm. 



Head, lateral aspect : The length of the head is three- 

 fourths the height. The face is almost completely plane 

 with the eye margin profile, a minute portion appears 

 at the level of the epistoma. The eyes are exceptionally 

 long and strongly convex anteriorly and almost equally 

 convex posteriorly on the upper half, moderately re- 

 cessive anteroventrally below ; the vertex appears above 

 the eye, The occiput is developed on the upper half, a 

 little more widely below due to the eye recession. The 

 pile of the occiput is short, fine and scanty below, absent 

 above, where there are 4 pairs of slender bristles, with 

 3 others between the eye margin and the ocelli. The 

 proboscis is short, obtusely rounded apically, subcylin- 

 drical from the dorsal aspect and gradually swollen 

 towards the base, and generally directed straight for- 

 ward; the apex and the base have a few fine hairs. 

 Palpus composed of two minute segments, the second 

 nonporate and carrying 1 or 2 fine hairs below, none at 

 apex. 



The antenna attached at the middle of the head ; an- 

 tenna long and slender, but shorter than head; the 

 first and second segments are of nearly equal length, 

 the third tapers from near its base to its apex, where it 

 bears 2 microsegments held at oblique angle; the first 

 microsegment is short, the second segment is 2 or 3 

 times as long and carrying an apical, spinous bristle, 

 which is as long as the first microsegment. The pile of 



