ROBBER FLIES OF THE WORLD 



523 



marginal and submarginal cells strongly expanded and 

 rippled. Marginal cell closed with a moderate stalk; 

 the anterior branch of the third vein ends just above 

 and the posterior branch ends just behind wing apex. 

 The anterior crossvein enters the discal cell at the distal 

 fourth. First 2 posterior cells widely open; fourth 

 posterior cell closed with a long stalk, the end vein 

 sinuous. The lower end vein of the discal cell is drawn 

 back almost as far as the radial medial crossvein, not 

 quite parallel with the wing margin. Anal cell closed 

 with a short stalk; second basal cell ends with two 

 veins and shortly fused beyond. Alula moderately 

 large ; ambient vein complete ; whole wing vitreous and 

 hyaline. 



Abdomen: The abdomen is subcylindrical, slightly 

 tapered and distinctly more narrow than the meso- 

 notum. The first tergite is a little swollen laterally. 

 Pile of abdomen short, fine and more or less appressed, 

 except along the sides and lateral margins of the first 

 two tergites, where it is especially long and quite fine. 

 Sides of first tergite with fine pile only ; tergal bristles 

 absent. Eight tergites present in the male but the 

 eighth present only laterally where, however, it is 

 rather long, still longer ventrally. Male terminalia 

 moderately elongate, not rotate, often directed upward. 

 The superior forceps largest and longest, appressed and 

 a little narrowed apically. Hypandrium quite short, 

 undivided. Sternites with only fine, long pile, con- 

 spicuously abundant on the second and third with some 

 &ie pile laterally on the firet sternite. Female un- 

 available. 



Distribution: Ethiopian: Hippomachus pegasus 

 Loew (1858). 



Genus Megadrillus Bigot 



FiGUBES 340, 725, 1453, 1463, 2233, 2348, 2349 



MegaiJrillus Bigot, Ann. Soc. Eut. France, ser. 3, vol. 5, p. 545, 

 1857. Type of genus : Loplianotus heteroneurus Macquart, 

 1838, by original designation. 



Eather small flies with tapered abdomen and strong 

 tergal and sternal bristles. The anterior femur is dis- 

 tinctly swollen. The anterior dorsocentral bristles are 

 long and prominent and the acrostical bristles likewise. 

 The face is shortly produced tliroughout its height and 

 very gently convex, with a medial band of stiff, long 

 pile. The face is very similar to N eolophonotus Engel 

 to which it is related. It is readily separated from its 

 allies by the first posterior cell wliich is closed with 

 a rather long stalk. Length 12 to 15 mm. 



Head, lateral aspect: The face is moderately pro- 

 duced and on the whole rather short ; it is a little more 

 prominent below, due to the recession of the eye, but is 

 gently convex and somewhat receding ventrally. The 

 eye is long, very convex anteriorly, a little narrowed 

 below and strongly, anteroventrally recessive on the 

 lower fourth. The remainder of the posterior profile 

 is slightly convex and becomes strongly convex near 

 the vertex. Pile of occiput rather dense, long, and 

 comparatively fine on the lower half, especially long 



posteriorly ; it is replaced by bristles beginnhig at the 

 middle of the head, where there tend to be 5 or 6 pale 

 pairs of bristles in at least 2 species. The dorsal bristles 

 are black and stouter; at first short, they become quite 

 long and strongly proclinate beliind the upper eye 

 cornei-s. There are 10 to 12 pairs of black bristles; 5 

 are long, 3 or 4 of medial length and the lowermost ele- 

 ments short. The occiput is moderately thick through- 

 out. The proboscis is comparatively short, rather slen- 

 der and cylindrical with a low, distinct, medial ridge 

 and a short swelling at the basal third ; apex with some 

 stiff, bristly hairs on each side above and below. The 

 base beai-s a few long hairs ventrolaterally ; the pro- 

 boscis is directed chiefly downward. Palpus compara- 

 tively short,, cylindrical with 5 or 6 stiff, long bristles 

 apically. 



The antemia is attached just above the middle of the 

 head and is slender but rather short; the first two seg- 

 ments are nearly equal in length. The tliird segment 

 is barely longer than the combined length of the first 

 two, slightly compressed laterally; of nearly uniform 

 width, it may be a little widened subdistally. There is 

 a distinct though short microsegment followed by a 

 short, thick style with apical spine; the style is only 

 half as long as the tliird segment; the first segment 

 bears ventrally 5 or 6 exceptionally stout, long, black 

 bristles, longer than the third segment. Second seg- 

 ment ventrally with at least 5 sunilarly long, stout, 

 apically tliick bristles; both segments with 5 or 6 xm- 

 usally long, stout, dorsal setae. 



Head, anterior aspect: The head is nearly circular; 

 the face below the antenna is about a fourth the head 

 width, wider below. Subepistomal area small, short, 

 very deeply concave and strongly oblique, pubescent 

 only anteriorly in the middle. The face bears numer- 

 ous, densely beset, long, pale, bristly haire or extremely 

 slender bristles, occupying a wide band down the middle 

 of the face. They begin immediately beneath the 

 antenna, are curled downward, the lower elements 

 straight, reaching to the apex of the proboscis. The 

 lateral margins of the epistoma have numerous, pale or 

 dark bristles which may be distinctly more stout than 

 the facial elements. Front short, pollinose with 4 or 5 

 rather long, slender bristles behind the eye margin. 

 Vertex only moderately excavated on each side of the 

 ocellarium but deeply behind; ocellarium of medium 

 size and height with but 2 pairs of moderately slender, 

 black bristles in the middle and 2 or 3 additional pairs 

 behind the ocelli. Anterior eye facets only slightly 

 enlarged. 



Thorax : The thorax is pollinose and strongly abrupt 

 anteriorly. Pile of mesonotum scanty, fine and bristly, 

 pale and dark, somewhat more abimdant over the 

 postalar and with a dense, narrow, longitudinal band 

 of pile in the middle of the mesonotum on the posterior 

 half, pale, long and bristly. On the anterior half is 

 a double, irregular row of exceptionally stout, long, 

 acrostical elements and beginning a short distance be- 

 hind this row there are 4 or 5 pairs of equally long. 



