ROBBER FLIES OF THE WORLD 



577 



like; female terminalia small, short and inconspicuous. 

 The mesonotum has prominent bristles anteriorly but 

 no mane. Lateral tergal bristles are restricted to the 

 first tergite but the remaining tergites bear postmar- 

 ginal bristles. Length 12 to 20 mm. 



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

 the eye is strongly convex anteriorly. The face is 

 strongly gibbose on the lower half, or sometimes a little 

 more than the lower half with the upper portion of face 

 plane with the eye. The occiput is only moderately 

 developed and bears long, fine pile below; slender 

 bristles begin at the middle of the head and become 

 quite stout and conspicuous beliind each upper eye 

 comer. The proboscis is slender, extending a little be- 

 yond the face; the apex bears a few slender hairs, is 

 distinctly narrow and back from the apex tliere is a 

 groovelike constriction. The basal half of the ventral 

 surface bears a number of long, bristly hairs. Palpus 

 slender, cylindrical with numerous, long, slender 

 bristles. The antenna is attached at the upper third of 

 the head and is slender. The first segment is nearly 

 three times as long as wide and longer than the second 

 segment; they both bear long setae above and several 

 moderately long, stiff bristles below. Third segment 

 slender, narrowed only near the apex, and approximate- 

 ly as long as the combined length of the first two seg- 

 ments; it beai's a small, short, distinct microsegment 

 and a stout, rather slioit style with bristly apex. This 

 microsegment and style are approximately as long as 

 the third segment and this segment bears 1 or 2 dorsal 

 setae. 



Head, anterior aspect: The head is comparatively 

 narrow and not greatly wider than high. The face 

 below the antenna is narrow and is from a seventh to 

 an eighth the head width and strongly widened below. 

 Face cover consists of dense, appressed micropu- 

 bescence, the whole gibbosity bears long, slender bristles 

 restricted to the medial portion but extended down 

 the sides of the large, concave subepistoma. The outer 

 bristles tend to be black and there are often some 

 wliitish bristles in the middle. Front distinctly widened 

 but the vertex narrowed. Front poUinose witli long, 

 fine, bristly hairs laterally. The vertex is moderately 

 excavated, the ocellarium has steep sides and 2 or 3 

 slender bristles between the ocelli, and 1 or 2 pairs 

 behind the ocelli. 



Thorax : The mesonotum is moderately high, abrupt 

 anteriorly and strongly sloping posteriorly. It is al- 

 most bare with a patch of scattered, bristly hairs me- 

 dial to each humerus and a few behind. There is 

 present a well differentiated double row of slender 

 acrostical bristles. Dorsocentral bristles begin in the 

 middle of the mesonotum and may show as many as 

 7 very long elements in each row. Lateral bristles long 

 and sharp. There are 2 notopleural bristles, 2 supra- 

 alar, 3 on the postalar callosity and 2 or 3 pairs on the 

 margin of the scutellum. The scutellum is convex, pol- 

 linose with impressed rim and a few, fine, long hairs on 

 the disc. Lateral callosity of the metanotum with 



bristles and pile. Humerus with bristly hairs. Prono- 

 timi with weak bristles; upper margin of the meso- 

 pleuron with a fringe of long, slender, bristly hairs. 

 Postmesopleuron and upper sternopleuron with a little 

 stiff pile. Upper pteropleuron with 6 or 7 long, quite 

 slender bristles and a few bristly hairs. The meta- 

 pleuron has a conspicuous, vertical row of 8 to 10 rather 

 stout, quite long bristles with 2 or 3 additional ele- 

 ments and other long hairs continued on the hypo- 

 pleuron. Posterior coxa without conspicuous bristles. 

 Postmetacoxal area membranous; lateral and ventral 

 metasternum with pile; prostemum fully dissociated. 



Legs : The liind legs are slightly elongate, the anterior 

 and middle femora are more stout, especially toward 

 the base. The hind femur is comparatively slender. 

 The anterior surface of the first 4 femora and the dorsal, 

 lateral and ventral surfaces of the hind femur with 

 scattered, fine, appressed setae. There are some con- 

 spicuous bristles on the femiu", more on the tibia. Hind 

 femur with 5 ventrolateral bristles on the basal half, 

 2 or 3 weak bristles along the middle laterally, 3 strik- 

 ing, long, stout, attenuate bristles ventrally on the basal 

 half with about 3 other somewhat less conspicuous ven- 

 tral bristles. On the apical fifth dorsolaterally is a 

 long, veiy stout bristle and another beside it more dor- 

 sal in position, and beyond dorsomedially is a slender 

 bristle, with 2 small bristles on each side at the apex. 

 Hind tibia with 2 exceptionally long, conspicuous 

 bristles on the basal half dorsolaterally, 5 long and 5 

 short bristles dorsomedially and 3 moderately long, 

 anteroventral bristles. At the apex are 2 lateral, 2 

 ventral, and 1 doreal bristle. IMiddle femur with a long, 

 conspicuous bristle anteriorly on the outer third, a 

 weaker bristle at the basal third and 5 or 6 posteroven- 

 tral and posteromedial bristles chiefly on the basal half. 

 Middle tibia with at the middle a stout, long, anterior 

 bristle, another distally, 2 quite long dorsal bristles 

 along the middle, a weaker bristle before and after, and 

 with 1 conspicuous posterior bristle on the basal tliird, 

 2 weak bristles beyond. The anterior femur has slender 

 bristly hairs anterodorsally and posterodorsally. The 

 anterior tibia has 3 weak, basal anterodorsal bristles, 9 

 posterodorsal, 5 of which are strong and 4 very long, 

 conspicuous, posteroventral bristles. Claws sharp, 

 slender; the pulvillus well developed; the empodium 

 bladelike. 



Wings: The wings are subliyaline and rendered 

 darker by dense villi on the ai:)ical third, the anterior 

 and posterior margins. Marginal cell closed with a 

 long stalk, the anterior and posterior branches of the 

 third vein end an equal distance above and below the 

 wing apex. The second submarginal cell is rather wide 

 basally but widened entirely in front of the third vein. 

 The second posterior cell is much wider than the end 

 of the discal cell, the medial crossvein quite long, paral- 

 leling the wing margin, the upper portion of the an- 

 terior intercalary vein short. Posterior crossvein want- 

 ing. Alula well developed; ambient vein complete. 

 Stalk of the closed, fourth posterior cell is long. 



