DASTPOGONINAH 



ROBBER FLIES OF THE WORLD 



203 



bristles, containing a wide vertical band of numerous 

 slender elements, wispy at apex. Whole of the pro- 

 pleuron with fine pile and no bristles; remainder of 

 pleuron micropubescent and without pile. Presternum 

 dissociated. Metasternum pilose, laterally and below. 

 Postmetacoxal area membranous. 



Legs : All the femora are stout, a little swollen before 

 the middle; the pile is dense, rather fine and appressed 

 dorsally, laterally and anteriorly with long, ventral 

 fringes of fine, bristly hairs posteroventrally and an- 

 teroventrally on all pairs. Posterior coxa with a strong 

 anterior process. Bristles of the legs are stout basally, 

 attenuate, most prominent on the middle tibia and few 

 in number on the femora. Hind femur with 4 or 5 

 conspicuous, dorsolateral bristles and 2 others at the 

 apex, and weaker ones medially at the apex. Middle 

 femur with 2 anterior bristles on the outer fourth, 2 

 at the apex, and 1 posteriorly at the apex, besides 

 several anterior, long, bristly hairs. Anterior femur 

 with numerous, long, posterior, bristly hairs, similar 

 dorsal hairs and with 2 stout, posterodorsal, subapical 

 bristles. Hind tibia with 5 dorsomedial, 3 dorsolateral 

 and 3 ventrolateral bristles, the latter restricted to the 

 lateral half. Middle tibia with 4 anterodorsal, 3 or 

 4 posterodorsal, 5 or 6 posteroventral, 4 long, stout, 

 ventral bristles which begin near the base, and 2 stout, 

 distal anteroventral bristles. Apex of midtibia with 

 2 stout, spikelike, ventral bristles. Apex of protibia 

 without spines. Claws slender, sharp; pulvilli long 

 and slender, empodium long and quite slender. 



Wings: The wings are slender, the marginal cell is 

 widely open; base of second submarginal cell has a 

 characteristic spur; all posterior cells widely open, 

 the rectangular anterior crossvein enters the discal cell 

 at the middle; the third vein forks at or before the 

 posterior crossvein, end veins of the discal cell of equal 

 length. Anal cell open. The second basal cell ends 

 in 3 veins. Alula short, ambient vein complete. 

 Wings with spots on the crossveins and at forks. 



Abdomen: The abdomen is cylindroid, slightly 

 tapered at the base and nearly as wide as the meso- 

 notum. The pile is fine, scanty and appressed, the 

 surface pollinose. Males with seven tergites only ; the 

 seventh is from a third to half as long as the sixth. 

 Females with eight tergites, the eighth half as long as 

 the seventh. Male terminalia quite short and obtuse; 

 epandrium cleft and the lateral lobes rather widely 

 flared or divergent; proctiger small and short. As in 

 ~Wilcoxia James, the gonopod is thrust obliquely up- 

 ward and is well developed. Hypandrium prominent 

 and curving upward. The female bears acanthophor- 

 ites, each of which have 4 long spines. 



Distribution: Nearctic: Metapogon alhulus Melander 

 (1923) ; gibber Williston (1884) ; gilvipes Coquillett 

 (1904) ; pictus Cole (1916) ; punctipennis Coquillett 

 (1904). 



Neotropical: Metapogon incertus Becker (1919). 



Genus Ablaiaus Loew 

 Fioubes 141, 540, 1050, 1059, 1795, 1800 



Ablautu.i Loew, Berliner Ent. Zeitschr., vol. 10, p. 37, 18G6. 



Type of genus: Ablautus trifarius Loew, 1866, by monotypy. 

 Ablautatus Loew, Berliner Ent. Zeitschr., vol. 18, p. 377, 1874, 



laps u x. 



Small to medium size and rather slender, mostly 

 pale colored flies. The abdomen is robust basally, 

 rather short and tapered. They are readily recognized 

 by the long, slender claws, the absence of pulvilli and 

 the long, coarse, opaque, pale and often flattened pile. 

 The legs are very bristly, the surface pollinose. The 

 face has a dense, matted mystax, the head broad with 

 the front and vertex a little widened. Finally the 

 humerus has bristles and all of the posterior cells of 

 the wing are open, usually the anal cell as well. Length 

 6 to 12 mm. 



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

 with the eye on most of its length; the lower visible 

 portion is due to the recession of the eye, the face is 

 short, rounded, and receding ventrally. The eye is 

 strongly flattened anteriorly, considerably narrowed 

 ventrally, clue largely to the conspicuous anteroventral, 

 recession of the eye, which begins near the vertex leav- 

 ing the naturally thick and tumid occiput greatly 

 exposed over most of its length. The pile of the 

 occiput is abundant, extremely long and delicate, re- 

 placed by bristles only on the upper third, where there 

 are 7 pairs, on the outer part of the occiput and some 

 10 pairs irregularly placed behind the upper medial 

 portion of the head. From the dorsal aspect the vertex 

 is greatly excavated posterolaterally. Proboscis of 

 medium length and thickness, extending a short dis- 

 tance beyond the face ; it is slightly tapered from the 

 dorsal aspect, less so from the lateral view with the 

 apex either pointed or bluntly rounded and with a 

 well developed dorsal ridge extending over the middle 

 but disappearing at base and apex. Apex with only 

 a few minute hairs. The proboscis tends to be extended 

 chiefly forward horizontally or slightly downward. 

 Palpus is minute, short and cylindrical. 



The antenna is attached at the middle of the head, 

 comparatively elongate and distinctly slender, except 

 on the first segment which is short, robust and convexly 

 extended below ; the second segment is nearly equal in 

 length and beadlike. The third segment is at least 1% 

 times as long as the first two combined, basally not quite 

 as wide as the second segment, a little swollen at the 

 base, then distinctly narrowed above and below on the 

 apical third, gradually swelling distally until it is wider 

 than at the base. Apically this segment bears a long, 

 microsegment with an apical bristle ; sometimes there is 

 a very short, additional, basal microsegment. The first 

 segment characteristically has at least 3 stout, blunt, 

 spikelike bristles on its ventral surface of the second 

 segment. First segment laterally and dorsally with 

 long, bristly hair and setae, the second segment with 

 short, dorsal setae. 



