LEPTOGASTRINAH 



ROBBER FLIES OF THE WORLD 



301 



occiput exposed, and shallowly concave medially. 

 Proboscis slender, a little pointed at the apex and 

 gently narrowed toward the base. It has a few fine 

 hairs at the apex and 1 or 2 hairs ventrally near the 

 base. Palpus exceptionally minute. Antenna of the 

 usual form in Leptogaster with the style short. 



Thorax : The thorax is as in Leptogaster, the anterior 

 portion of the mesonotum tends to overhang the pro- 

 notum but is rounded and blunt. Surface pollinose 

 with a stout bristle on the notopleuron, one above the 

 base of the wing but with the postalar callosity and 

 scutellum only with 1 or 2 fine hairs and some pollen. 

 Disc of scutellum sometimes with very fine micro- 

 pubescence. 



Legs : The legs are not unusual except that the hind 

 femur tends to be rather more than ordinarily swollen 

 on the outer third and the outer two-thirds of the hind 

 tibia is likewise rather robust. The pile of the hind 

 tibia is moderately abundant, oblique and stiff but does 

 not form distinct bristles with the exception perhaps 

 of 1 or 2 weak elements at the apex and the midtibia 

 tends to have 1 or 2 long, quite slender, bristly hairs 

 ventrally. Empodium long and rather stout. 



Wings : The wings are slender and greatly narrowed 

 towards the base. Anal cell widely open, posterior 

 crossvein short or absent. Upper anterior intercalary 

 vein joins the first branch of the medius at or nearly 

 at a right angle. The posterior branch of the third 

 vein almost straight but the anterior branch rather 

 strongly arched and divergent. 



Abdomen: The abdomen is similar to Leptogaster 

 but with a circlet or band of hairs of variable length 

 around the middle of the second tergite. In some 

 species it is rather well developed, in others poorly 

 differentiated. The male superior forceps tapers to 

 a point and is often divergent laterally, expanded 

 apically and notched. The male terminalia have 

 primary, secondary and tertiary penis valves with a 

 medial process immediately below. 



Description drawn from paratypes of Beameromyia 

 lacinia, punicea, and chrysops. 



Subgenus Apachekolos Martin 



Apachekolos Martin, Bull. Amer. Mus. Nat. Hist., vol. 3, p. 

 352, 1957. Type of subgenus : Leptogaster scapularis 

 Bigot, 1878, by original designation. 



A small group of Leptogaster Meigen species in 

 which the female ninth tergite has two narrow, lat- 

 eral lobes forming a notchlike figure. The male su- 

 perior forceps are deeply forked with the lower arm 

 broader and wider than the dorsal prong. The femora 

 tend to be elongate and on the whole a little less cla- 

 vate distally than in Leptogaster in the restricted sense. 

 Five species were placed here by Martin ; Apachekolos 

 tenuipes Loew from the eastern and southern United 

 States, and Apachekolos scapularis, weslacensis, cri- 

 nita and confusio from the southwestern states. 



Genus Tipulogaster Cockerell 



FlGUEE 199 



Tipulogaster Cockerell, Entomologist, vol. 46, p. 214, 1913. 

 Type of genus: Leptogaster badius Loew, 1862, by orig- 

 inal designation. 



These flies differ from Leptogaster Meigen prima- 

 rily in the long, third antennal segment, which is quite 

 slender and attenuate and more than twice the com- 

 bined length of the short basal segments. The style 

 is not unusually long and, in fact, is comparatively 

 short in proportion to the length of the third segment. 

 The distal fork of the fourth vein is comparatively 

 close to the medial crossvein so that the upper ante- 

 rior intercalary vein is but little longer than the dis- 

 cal crossvein. In the type of genus of Leptogaster 

 this fork is closer to the anterior crossvein. Many 

 species of Leptogaster and Psilonyx Aldrich have the 

 venation rather similar on the whole to Tipulogaster 

 badius. 



From exotic genera with a similarly elongate third 

 antennal segment it is separated by the posterior ven- 

 tral encroachment of the lateral metasternum; these 

 2 extensions touch but do not fuse and a membranous 

 area remains behind the postcoxa. Also the third 

 antennal segment is not flattened and the hind femur 

 bears no medial hair flocks. The anterior branch of 

 the cubitus and the posterior branch of the medius 

 are fused for a considerable distance, perhaps twice 

 the extent found in Leptogaster cylindrica. The arms 

 of the superior forceps are of nearly equal width. 

 Primary penis valves situated in a U-shaped config- 

 uration and lying flatly on the dorsal surface of the 

 ninth sternite; between these arms are 2 lobes which 

 bear white hairs on their inner surfaces. Length 14 

 to 16 mm. 



Distribution: Nearctic: Tipulogaster badius Loew 

 (1862) [ = testaceus Loew (1862)]. 



Genus Psilonyx Aldrich 



Figuees 603, 2064 



Psilonyx Aldrich, Proc. U.S. Nat. Mus., vol. 62, p. 5, 1923. Type 

 of genus: Leptogaster annulatus Say, 1S23, by original 

 designation. 



This genus is quite like Leptogaster Meigen, being 

 distinguished by the complete absence of empodium. 

 The fork of the first branch of the medius is distal, 

 opposite the posterior crossvein and no longer than it. 

 Length 10 to 15 mm. 



Head, lateral aspect : The head is similar to Lepto- 

 gaster but a little longer, strongly convex anteriorly 

 and posteriorly with prominent occiput over the middle 

 of the head and weak supraoccipital bristles. The face 

 tends to be greatly reduced by an encroacliment of 

 the eye almost to the point of holopticism and the 

 central anterior facets are very greatly enlarged. Head 

 and antenna otherwise as in Leptogaster. 



