ROBBER FLIES OF THE WORLD 



525 



the genus from the Oriental Clephydroneura Becker; 

 both genera have the fourth posterior cell bulging an- 

 teriorly. Length 20 to 25 mm. 



Head, lateral aspect: The face is moderately pro- 

 duced and visible throughout its entire extent, but 

 without ventral protuberance. The anterior profile is 

 slightly convex. The eyes are recessed below beginning 

 only at the lower sixth. The anterior profile is convex 

 and the posterior profile is nearly plane through the 

 middle. The occiput is rather prominent throughout 

 the entire length, except at the immediate vertex, where 

 it is obliterated. The pile of the occiput is very scanty 

 above and becomes rather long and abundant at the 

 middle and below. Bristles begin at the middle and 

 consist of 13 pairs ; the upper 3 or 4 pairs are stouter 

 and strongly proclinate. The proboscis is subcylindri- 

 cal, swollen only at the immediate base, the apex wide, 

 obtuse, very slightly tapered above and below and with 

 stiff, apical pile ; the base bears a few, long, stiff hairs ; 

 proboscis directed obliquely forward. Palpus of one 

 segment with a fused, basal trace of an additional seg- 

 ment; it is cylindrical and robust, and bears several, 

 long, stout, apical bristles. The antenna is attached at 

 the upper third of the head. The first two segments are 

 slightly elongate, of nearly equal length but the second 

 slightly shorter. The third segment is three-f ourtlis of 

 the combined length of the first two segments; it is 

 slender, bears a short microsegment followed by a short, 

 thick style. This style, together with microsegment, is 

 as long as the third segment, and bears a minute spine 

 apically. First and second segments with short setae 

 dorsally and long, oblique bristles and setae below; at 

 least 1 bristle at the apex of the second segment is stout ; 

 third segment with 2 or 3 setae dorsally. 



Head, anterior aspect : Face below the antenna a fifth 

 the head width and divergent below. Subepistoma 

 small, strongly oblique, plane and pubescent. Face 

 pubescent with stiff, short pile down the middle begin- 

 ning at the base of the antenna and bearing 4 pairs of 

 stout, long bristles across the epistomal margin with 2 

 pairs of bristles lying immediately above these ; in the 

 middle on the lower half of the face there are several 

 additional, weaker bristles. Front short, slightly di- 

 vergent, the vertex more strongly convergent; sides of 

 front with 4 moderately stout bristles. Vertex deeply 

 excavated with nearly vertical sides. Ocellarium low 

 with 3 pairs of short, slender bristles. Eyes with cen- 

 tral facets enlarged. 



Thorax : The mesonotum and pleuron pollinose. The 

 pile of the mesonotum is unusually scanty. Acrostical 

 elements absent. The medial third of the mesonotum 

 is without pile. Dorsocentral elements short, few and 

 scattered but beginning at the middle and extending 

 back to the scutellum there are 7 long, stout elements 

 in this series. Humerus with a few hairs. Stout, long, 

 lateral bristles ai'e present and consist of 2 notopleural, 

 1 postsupraalar, 1 suprapostalar, with sometimes addi- 

 tional smaller bristles, 2 to 3 postalar and 1 pair of 

 scuteUar bristles set rather close together. Scutellum 



thick and convex, with impressed rim, with 3 or 4 pairs 

 of setae on the margin and 12 erect, fine setae on each 

 side of the disc ; the disc pollinose. Pleuron with abun- 

 dant, stiff pile, the pronotum with 2 pairs of weak 

 bristles. Mesopleuron with a few, scattered, fine hairs 

 dorsally, posteriorly and on anterior process. Stemo- 

 pleuron above with 2 or 3 fine hairs. Posthypopleuron 

 with a row of 6 distinct, moderately long bristles. 

 Metapleuron with a row of 7 or 8 longer bristles. Up- 

 per pteropleuron with a tuft of pile. Metanotal slopes 

 micropubescent only. Lateral and ventral metaster- 

 nmn with numerous, long, fine hairs. Postmetacoxal 

 area membranous and pollinose ; tegula pubescent only ; 

 squama with a fringe in several rows. 



Legs : The femora are stout, the anterior and middle 

 pairs slightly thickened toward the base, all pairs with 

 appressed, numerous, short setae above ; bristles where 

 present quite stout and moderately long. Ventral sur- 

 faces with scanty pile. The hind femur bears 2 or 3 

 medial and 3 dorsolateral bristles at apex, and some 

 distance back from apex 1 dorsomedial and 1 dorso- 

 lateral bristle, the latter forms part of a row of 4 

 bristles. Ventrolateral margin with 6 stout bristles; 

 ventromedial margin with 4 longer, stout bristles and 

 up to 3 bristles medially at the base. The hind tibia 

 bears moderately long bristles, 3 dorsal, 3 lateral, and 3 

 ventrolateral on the outer half; apex with 2 dorsal, 2 

 lateral, 2 medial, and 4 ventral bristles ; medial surface 

 with brush of setae. Middle femur with 3 anterior, 5 

 anteroventral and 3 posterior bristles near the apex. 

 This tibia bears 3 weak posterodorsal, 1 stout dorsal 

 near the apex, 5 cluefly weak posteroventral, 4 stout, 

 anteroventral bristles. Anterior femur with bristles 

 restricted to the basal half of the ventral surface, where 

 there are 3 to 6 long bristles present; its tibia has 3 

 short dorsal, 4 long posteroventral, quite stout and 

 otherwise with only short setae. Tibia end in long pul- 

 villi and stout empodium three-fourths as long as 

 pulvilli ; claws moderately sharp. 



"Wings: The wings are slender and hyaline. Mar- 

 ginal cell closed and stalked. The anterior branch of 

 the third vein ends barely before apex. Fourth pos- 

 terior cell closed and stalked and characteristicaUy 

 strongly convex anteriorly, reducing the width of dis- 

 cal cell to half. Second basal cell ends in 2 veins ; anal 

 cell closed ; alula large, the ambient vein complete. The 

 anterior cells are rippled without expansion. 



Abdomen: The abdomen is comparatively slender 

 and tapered, as long as the wings and slightly longer. 

 First tergite slightly swollen laterally and rigid. Pile 

 of abdomen scanty, fine, appressed and setate. First 

 five or six tergites with distinct bristles which are 

 rather stout on the first tergites. First tergite with 2 

 pairs, subposterior margin of second tergite with 2 or 

 3 stout pairs; third tergite with 3 weaker bristles; 



