DASirOGONINAE 



ROBBER FLIES OF THE WORLD 



215 



parallel sides; inystax ascending to one-third of the face; eyes 

 large, prominent. Antennae slender ; the third joint much 

 longer than the basal joints together, pointed at the tip ; 

 terminal style distinct, elongate, two-jointed. Thorax and 

 scutellum without bristles ; the abdomen long and slender ; the 

 anal segment (female) with some small spines. Legs mod- 

 erately long, the hind pair scarcely longer and somewhat more 

 robust than the others ; first tarsal joint as long as the two or 

 three following joints together ; foot-claws long ; pulvilli absent. 

 In the wings all the posterior cells are open and not constricted ; 

 the fourth posterior cell issues from the second basal cell ; the 

 third basal cell is closed at the margin of the wing. 



This genus is related to Rhadinus, but differs in the mystax, 

 which does not ascend to the antennae ; the total want of bristles 

 on the thorax and scutellum ; the less excavated front, the more 

 elongate antennae, and the not closed fourth posterior cell. 

 From Leptogaster it differs in the hind legs, which are less 

 elongate and of which the femora and tibiae are not club- 

 shaped, the tibiae being gradually and only slightly enlarged 

 towards the tip. 



Genus Lycostomus Hermann 



Figuees 535, 1104, 1113, 1755, 1862 



Lycostomus Hermann, Zeitschr. syst. Hymen, und Dipt., vol. 7, 

 p. 4, 1907. Type of genus: Lycostomus albifacies Hermann, 

 1907, by original designation. 



Flies of medium size, which will be rather readily 

 recognized by the ventrally produced and beaklike face, 

 together with the almost complete absence of excavation 

 at the vertex. Wings hyaline with generalized vena- 

 tion. Its relations are dubious. While Ancylorrhyn- 

 chus Latreille has no vertical excavation, its peculiar 

 proboscis sets it rather far from Lycostomus. Length 

 12 mm. 



Head, lateral aspect : The head is long and accentu- 

 ated by the added length of the conical, peaked, and 

 produced face. The face is extended forward to an 

 increasing extent toward the bottom of the head, with 

 the ventral surface plane and truncate. This results in 

 the face appearing as a prominent, bluntly pointed cone. 

 The occiput is prominent and the pile of the occiput and 

 vertex is fine and white, rather long over the occiput; 

 bristles absent. Posterior eye margin rather strongly 

 convex and the eye descends below the face. Epistomal 

 area large, slightly oblique and exposed. The proboscis 

 is short, slightly attenuate, directed obliquely forward, 

 its apex short pilose. Palpus of two segments; the 

 second segment is a little shorter and apparently more 

 or less fused, but both cylindrical ; the apical segment 

 is distinctly opened and porous apically. Basal seg- 

 ment split along the dorsomedial surface. The antenna 

 is missing from the unique type. 



Head, anterior aspect: The face is unusually wide, 

 more than a third the head width and the sides parallel. 

 It is densely white pollinose and this same pollen extends 

 over the front and vertex. Middle apex of face with a 

 few, short, downwardly directed, stout, yellowish white 

 bristles in 2 rows; the total number of bristles is 18. 

 The front and vertex are considerably expanded, the 

 vertex not at all excavated. Ocellar protuberance ex- 

 tremely low, slanting backward, bearing minute hair. 



535914— 62— pt 1 15 



Thorax : The mesonotum is everywhere densely, grey 

 pollinose and with rather fine, subappressed, greyish 

 white pile. The humerus is orange brown and pilose. 

 The short, rather weak, white lateral bristles consist 

 of 3 notopleural, 3 supraalar, 1 postalar, and 2 pairs 

 of bristles on the scutellum, the outer pair weak and 

 both pairs convergent. The flat scutellar disc has 15 

 to 20 convergent hairs. There are bristles on the 

 pleuron but the pronotal collar and whole propleuron 

 is densely long, white pilose. The propleuron is fused ; 

 hypopleuron pubescent only; mesopleuron pilose be- 

 hind and above; pteropleuron pubescent only; meta- 

 pleuron with 5 or 6 weak, short, slender bristles. The 

 metanotal slopes are bullose and micropubescent only. 



Legs: The hind femur is rather strongly thickened 

 through the middle, narrowed at the immediate apex 

 and for a somewhat longer distance basally. It is a 

 little more than twice as thick distally as basally. The 

 bristles are extremely short, stout, pale and tuberculate. 

 The bristles of this femur consist of 2 lateral at the 

 apical third, 1 dorsal near the apex, and 3 ventro- 

 lateral at the apical third, besides 3 or 4 ventromedial 

 elements at the outer half. The pile is dense, short, 

 quite flat appressed and pale brownish red or yellow. 

 The femur is slightly elongate. The tibia is equally 

 long, slender at base, iy 2 times as thick apically witb 

 double lateral row of minute, short, yellow bristles; 

 each row contains 4 or 5 bristles, and there is an addi- 

 tional double row of 3 or 4 longer, ventral bristles 

 confined to the outer half. Tarsus short, the basitarsus 

 as long as the next two segments. The middle and 

 anterior femora are apparently without bristles. The 

 middle tibia has 5 rather short, posteroventral, 5 short 

 dorsal, 4 short anteroventral bristles, and the anterior 

 tibia has 4 to 6 extremely short dorsal bristles or setae 

 extending the full length of the tibia and also with 

 slightly longer, posteroventral bristles on the outer 

 half and 6 to 7 short posterior bristles. Apex with 

 a circlet of spines on the lower half and 2 dorsal bris- 

 tles. No spine present. The tarsi are short, the claws 

 moderately long, sharp and arched from the base, and 

 the pulvilli nearly as long as the claw, rounded api- 

 cally; empodium nearly as long as pulvilli. 



Wings: The marginal cell is widely open. Fourth 

 posterior cell is closed in the margin; anal cell nar- 

 rowly open. The second posterior cell is open the full 

 width but both the end veins of the discal cell are 

 nearly equal in length, the upper one shorter; second 

 basal cell ends in three veins, middle vein shortest; 

 alula large, the ambient vein complete. 



Abdomen : The abdomen is cylindrical, the first tergite 

 rather short with slightly overlapping edge laterally and 

 a medial crease anteriorly. On the sides the abdomen 

 is slightly narrowed from the base of the second tergite 

 and the remaining tergites are progressively narrowed ; 

 the sixth tergite is less than one-third the length of the 

 second tergite, slightly longer than the first and three 

 times as long as the seventh. Sides of the first tergite 

 with 5 or 6 short, white bristles and considerable brown- 

 ish white pile. Remaining tergites without lateral bris- 



