ROBBER FLIES OF THE WORLD 



497 



especially thick and well developed at the bottom of 

 the head, due largely to the recession of the eye ; it bears 

 abundant, fine, long hairs on the lower half; bristles 

 begin at the middle and consist of about 20 stout, short, 

 brownish yellow bristles. The proboscis is robust, ex- 

 tends beyond the face and obliquely downward ; it bears 

 a few fine hairs at the apex and numerous, quite long 

 hairs ventrally on the whole basal half; medial dorsal 

 ridge absent. Palpus moderately long and slender, with 

 numerous, long, fine, bristly hairs. The antenna is at- 

 tached below the upper third of the head; exclusive of 

 the style, it is much shorter than the head. The first 

 segment is 5 or 6 times as long as the very short second 

 segment. The third segment is short oval, quite small, 

 narrow, and a little attenuate apically ; it bears a short, 

 distinct microsegment and a slender style, which is ap- 

 proximately as long as the first two antennal segments. 

 First and second segments with unusually narrow, long, 

 setae-like, bristly hairs dorsally, laterally, and below; 

 these tend to form a single circle on the second segment. 



Head, anterior aspect: The head is nearly circular. 

 The face beneath the antenna is about a fourth the head 

 width and only slightly widened below. The flat por- 

 tion of the face below the antenna is without pile. 

 There are very numerous bristles or bristly hairs over 

 the whole gibbosity, arising even from the nearly hori- 

 zontal upper ledge ; these bristles on the upper, convex 

 margin of the protuberance are shorter; those on the 

 lower half are much longer but also slender; similar 

 elements extend down the sides of the subepistoma. 

 The front laterally bears unusually numerous, long, 

 slender, curled bristles with at least 20 on each side. 

 Vertex deeply excavated, with slantmg sides ; the ocel- 

 larium is small and low and bears 6 long, slender, black 

 hairs on each side. 



Thorax : The mesonotum has an irregular, acrostical 

 band of stiff, short, suberect, blackish setae and similar, 

 slightly longer, stiff, black pile in the dorsocentral 

 area. Humerus with black and yellow pile without 

 bristles. The lateral bristles are long and stout and 

 consist of 3 notopleural, 1 supraalar, and 2 postalar 

 brownish yellow bristles. On the outer third of the 

 scutellum is a band of long, somewhat curved, upwardly 

 turned, moderately stout, brownish yellow bristles; the 

 actual marginal members are more slender and merge 

 into fine, long, slender hairs laterally and toward the 

 base; in addition there are at least 6 pairs of rather 

 stout, submarginal bristles. On the mesonotum are 4 

 long, stout, brownish yellow, prescutellar, dorsocentral 

 bristles mixed with 1 or 2 finer, black bristles ; the post- 

 alar also bears some long, slender, black bristles. Pro- 

 notum with 5 pairs of bristles and metapleuron with a 

 wide, vertical band of weak, long, brownish yellow 

 bristles. Upper stemopleuron, lower postmesopleuron, 

 pteropleuron and hypopleuron, and the sides of the 

 metasternum all with abundant, long, brownish yellow 

 pile; metanotal slopes bullose, but without bristles or 

 pile. Postmetacoxal area membranous. 



Legs : The hind femur is stout, the middle and an- 

 terior femora a little more thickened, especially towards 



535914— 62— pt. 2 6 



the base. All pile and bristles are pale brownish yellow 

 on the femora; the pile is dense and mora or less ap- 

 pressed, rather long and fine. The ventral surfaces 

 bear a few, fuie, long, scattered, erect or nearly erect 

 hairs; the dorsomedial or posterior margins of all of 

 them bear long, extremely fine hairs disposed in a sparse 

 fringe, which is especially long on the anterior femora. 

 The stout bristles of the hind femur consist of 3 lateral, 

 6 ventrolateral, 3 ventral at the basal third, and 4 ven- 

 tromedial bristles, 3 dorsal subapical and 1 medial 

 bristle at the apex. The hind tibia has 4 dorsal bristles 

 submedially, 1 quite at the base and the last dorsal 

 element just beyond the middle, 1 dorsolateral, 3 ven- 

 trolateral bristles; apex with 2 ventral, 2 lateral, 1 

 dorsal bristle. The middle femur has a very conspic- 

 uous, anterior and posterior row, 4 anteriorly and 5 

 posteriorly ; also 1 exceptionally stout, posterior bristle 

 near the apex and 6 ventral elements, the one at the 

 base doubled. Middle tibia with a divergent, double 

 ventral row of 3 bristles beginning just before the 

 middle, and with 2 dorsal bristles on the apical third ; 

 this tibia also has very long, fine hairs dorsally and 

 anteriorly and 4 very stout posterior bristles. The an- 

 terior femur has 6 long, strong bristles ventrally, all 

 on the basal half. Anterior tibia with a double, dorsal 

 row of shorter bristles, 5 anterior and 3 posterior, be- 

 sides a more posterior row of irregular, quite long, very 

 stout bristles, 5 in number. The claws are long, stout, 

 bluntly pointed at apex ; pulvilli two-thirds as long as 

 claws; empodium stout, bladelike and four-fifths as 

 long as claw. 



Wings : The wings are slender but with the axillary 

 lobe distinctly expanded and an incisionaiy notch pres- 

 ent at the end of the anal vein. The subcostal cell is 

 narrowed at the expense of the marginal cell ; marginal 

 cell closed with a rather long stalk. The second sub- 

 marginal cell has nearly parallel sides and originates 

 far beyond the end of the costa and both branches of 

 the third vein end above the wing apex ; the first branch 

 of the fourth vein ends far to the rear of the wing apex 

 and, since the second posterior cell is greatly widened 

 just beyond its base and mostly anteriorly, the first 

 posterior cell is in consequence greatly occluded in the 

 middle ; lower end vein of discal cell drawn backward ; 

 fourth posterior cell closed with a long stalk; its an- 

 terior margin strongly convex, occluding the discal cell. 

 Anal cell closed and stalked ; second basal cell ends in 

 two veins, fused briefly beyond; alula large; ambient 

 vein complete. 



Abdomen: the abdomen is cylindroid, tapered; the 

 sides of first tergite bear a tuft of abimdant, stiff, 

 brownish yellow pile and a vertical row of 3 long, 

 stiff, stout, reddish brown bristles; remainder of seg- 

 ment without special pile or bristles. All the abdominal 

 pile is nearly flat appressed and brownish white. Males 

 with prominent terminalia, not rotate, and with the 

 elongate, superior forceps and the gonopod elevated. 

 The superior forceps with terminal, winglike process 

 as in some species of Nerax, new genus, and the two 



