ROBBER FLIES OF THE WORLD 



499 



pubescent. Metasternum pilose; postmetacoxal area 

 membranous; presternum dissociated. 



Legs : The femora are stout, the first four a little swol- 

 len dorsally, but plane below ; the pile is rather abim- 

 dant on the dorsal or lateral surfaces, coarse and com- 

 paratively long and flat appressed. There are fringes 

 of longer, fine, stiff hairs on the lateral, dorsomedial, 

 and the lower half of the medial surface of the hind 

 femur and the ventral surface of hind tibia; also on 

 the anteroventral and ventral surfaces of the middle 

 femur and especially on the ventral surface of the an- 

 terior femur and its tibia. Bristles are comparatively 

 stout and numerous. The hind femur has 5 dorsolateral, 

 6 or 7 ventrolateral, and the apex and subapex with dor- 

 somedial bristles. Hind tibia with 4 dorsolateral, 4 

 dorsomedial, and 3 ventrolateral bristles, the apex with 

 5 bristles. Coxa laterally with 2 or 3 bristles and bristly 

 hairs. Post-trochanters with 2 bristles. Middle femora 

 with 2 bristles posteriorly on the basal half, 2 or 3 an- 

 teriorly on the basal half ; and with 3 or 4 anteroventral 

 bristles besides 4 or 5 ventral bristles on the basal half. 

 Anterior femur either without bristles or in some species 

 witli 6 ventral bristles on the basal half and some pos- 

 teroventral bristly hairs. Tibia with the bristles similar 

 to the hind pair, but with 2 or 3 much longer, postero- 

 ventral bristles. Claws slender but only moderately 

 sharp ; the pulvilli are long but only four-fifths as long 

 as the claw, empodium bladelike. 



Wings: The wings are hyaline, the marginal cell 

 broadened in the male and less broadened in the female 

 at the expense of the subcostal cell. The anterior branch 

 of the third vein ends shortly before the wing apex and 

 the posterior branch distinctly but shortly behind the 

 wing apex. The anterior branch arises rather abruptly. 

 Fourth posterior cell closed and stalked, the anal cell 

 likewise. Alula large, the ambient vein complete. 



Abdomen : The abdomen is slender and tapered ; only 

 the first segment is as wide as the mesonotum ; the pile 

 is coarse, suberect, comparatively long, but scanty and 

 distinctly longer on the sides of the first three tergites, 

 but likewise sparse. First tergite with 3 or 4 stout 

 bristles, the posterior margins of the second and third 

 and sometimes the fourth segments with a subapical, 

 sublateral patch of weak bristles. Males with eight 

 tergites, the eighth quite narrow and in the middle 

 sometimes reduced to membrane. Females with seven 

 tergites, excluding the ovipositor. Male terminalia 

 rather short, the superior forceps divergent, the gono- 

 pod small. The hypandriimi is boatlike and in some 

 species rather elongate. The female terminalia consist 

 of a long, slender, cylindical cone, composed chiefly of 

 the eighth segment; the ninth and tenth segments are 

 both short, the tenth has on each side 5 or 6 spikelike 

 spines and the sternite below bears sharp, stubby setae. 



Distribution: Nearctic: ProctacantheUa cacofilogus 

 Hine (1909) ; janiesi Pritchard (1935) ; leucopogon 

 Williston (1893); robusta Bromley (1951); wilcoxi 

 Bromley (1935). 



Genus Senoproposis Macquart 



FiouBES 334, 700-703, 1479, 1488, 1492, 1501, 2312, 2356, 2456 



Senoprosopis Macquart, Dipteres exotiques, vol. 1, pt. 2, p. 130, 

 1838. Type of genus : Senoprosopis diardii Macquart, 1838, 

 by monotypy. 



Stenoprosopis Kert^sz, Catalogus dipterorum . . ., vol. 4, 1909. 

 Emendation. 



Eather small, quite slender flies. The abdomen is as 

 long or slightly longer than the wings. The hind femur 

 and tibia are lengthened and all the legs are somewhat 

 longer than usual. These flies are pollinose, dark 

 colored and their legs are usually with yellow markings. 

 They are characterized by the very slender face, the 

 not impressed scutellum, the pilose, lateral slopes of the 

 metanotum, the short third antennal segment and the 

 long, slender style. The face is scarcely produced be- 

 yond the eye margin; it follows the curvature of the 

 eye and is, therefore, convex. Length 12 to 16 mm. 



Head, lateral aspect: The face is quite short, very 

 slightly longer toward the epistoma ; the whole face is 

 rather strongly convex, especially on the lower half ; in 

 general it tends to follow the eye margin. Eye strongly 

 oval anteriorly; plane through the middle posteriorly, 

 strongly recessive anteroventrally and also plane on the 

 lower fifth. The occiput is short, uniformly developed 

 from vertex to the cheeks; the pile is fine but only 

 moderately long and rather abundant on the lower 

 third, scanty in the middle and dorsally. There are a 

 few quite slender bristles which begin on the upper 

 third and consist of 8 or 9 pairs ; the 2 or 3 most dorsal 

 elements on each side are strongly proclinate. The 

 proboscis is slender, bluntly pointed at the apex and 

 very gently constricted in the middle especially on the 

 lower aspect; it is without dorsal ridge, except for a 

 basal trace and bears a few, fine, stiff hairs ventrally ; 

 it extends very little beyond the face and is directed 

 obliquely forward. Palpus quite slender, elongate with 

 bristly hairs dorsally and laterally and a single long, 

 bristly hair at the apex. The antenna is attached at the 

 upper third of the head and is comparatively short; 

 the first segment is twice as long as the second. The 

 third segment is only as long as the first and slightly 

 widened at or beyond the middle; it is attenuate api- 

 cally but abruptly, without microsegment and carries 

 a long, slender, bristle-tipped style, at least li/^ times 

 as long as the combined length of all of the segments. 



Head, anterior aspect : The face at the antenna is a 

 seventh the head width and divergent below. The face 

 is densely appressed pubescent and down the middle 

 bears 3 or 4 fine hairs and in the middle 3 or 4 long, 

 slender, bristly hairs not quite as long as the first 3 

 antennal segments. Ventrally in the middle is a tri- 

 angular patch of 5 or 6 long, pale, slightly stouter bris- 

 tles, and similar bristly hairs down the sides of the 

 subepistoma; the subepistoma is comparatively small, 

 narrow, concave, pubescent and oblique. The first seg- 

 ment of the antenna has 2 or 3 bristly setae ventrally 

 and dorsally; second segment with a like number ven- 



