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UNITED STATES NATIONAL MUSEUM BULLETIN 22 4 



Thorax: The thorax is similar to Leptogaster. 



Legs: The hind femur is strongly dilated beyond 

 the middle; on the whole, this pair of legs is some- 

 what less elongate than in many species of Leptogaster. 



Wings : In the wings the anterior crossvein is rectan- 

 gular, entering the discal cell opposite the end of the 

 second basal cell. The end veins of the second basal 

 cell are generally not or but little fused. The third 

 vein forks opposite or even a little before the pos- 

 terior crossvein. 



Abdomen : The abdomen is similar to Leptogaster. 



Distribution: Nearctic: Psilonyx annulatus Say 

 (1823) [=Aisfrw Wiedemann(1828)]. 



Neotropical: Psilonyx macropygialis Williston 

 (1901) ; magnicauda Curran (1934) ; micropygialis 

 Williston (1901). 



Palaearctic: Psilonyx annuliventris Hsia (1949); 

 humeralis Hsia (1949). 



Oriental: Psilonyx nigrlcoxa Hsia (1949). 



Genus Sinopsilonyx Hsia 



Sinopsilonyx Hsia, Sinensia, Academia Sinica, Nanking, vol. 19, 

 p. 27, 1949. Type of genus : Sinopsilonyx tibialis Hsia, 

 1949, by original designation. 



This genus is allied to Psilonyx Aldrich, and I quote 

 the original description : 



Allied to Psilonyx, distinguished by the ernpodia present 

 though rudimentary, the disc of mesonotum shining and bare, 

 the tibia lateraUy flattened and the apical segment of hind tarsi 

 hump-backed. 



Head widely transverse, wider than the thorax ; face very 

 narrow ; mouthedge slightly produced in front and bearing a 

 few weak bristly hairs ; hind head tomentose but without strong 

 postocular bristles ; ocelli placed on a bare elevated knob. 

 Proboscis long, extending out horizontally ; palpi one-segmented. 

 Antennae (Fig. 4, A) closely approximate at the base, not longer 

 than the head ; two basal segments equally short, third segment 

 long-oval, about as long as two basal together ; style linear, 

 about twice as long as the third segment. Collar short and bare. 



Thorax somewhat globular, almost shining and bare; 

 praesutural and supra-alar bristles present ; pleura covered with 

 tomentum. Scutellum small, concealed beneath the scutellum. 



Abdomen very long and slender, dangling downwards, slightly 

 widened at the apex, covered thinly with tomentum and hairs 

 especially on the terminal segments. Genitalia of the male 

 rather knobbed and complex. 



Legs long and thin, the hind femora distinctly clavate, the 

 hind tibiae (Fig. 4, B) dilated in the middle and slightly bi- 

 laterally compressed ; the legs are almost unarmed, but the 

 femora have some subapical bristles, the tibiae have incon- 

 spicuous bristly hairs on the upper-inner side and with long 

 thin spurs. Tarsi with strong bristles at the tip of each of the 

 first four segments; the apical segment (Fig. 4, B) of hind tarsi 

 strongly convex, thickened and slightly longer than basal seg- 

 ment ; the three middle segments equally short and together 

 about as long as the basal. Pulvilli absent, claws long and 

 gently curved. Empodia (Fig. 2, B) rudimentary. 



Wings small, shorter than abdomen ; marginal cell wide open ; 

 anal cell open, long and narrow, but dilated at the middle and 

 convergent to the wing margin ; no small cross-vein. Halteres 

 with an usually long stem. 



Distribution: Palaearctic: Sinopsilonyx tibialis Hsia 

 (1949). 



Genus Mesoleptogaster Frey 



Fiouees 193, 604, 1179, 1187, 1589A-C, 2046, 2054 



Mesoleptogaster Frey, Notulae Entomologicae, Helsinki, vol. 17, 

 p. 40, 1937. Type of genus: Mesoleptogaster fuscatipennis 

 Frey, 1937, by original designation. 



These flies were separated from Leptogaster Meigen 

 by the presence of strong bristles on the outer margin 

 of the hind tibia and the relative length of the third 

 antennal segment which is four times as long as broad. 

 In other respects this genus is quite like Leptogaster. 

 Length 9 to 18 mm. 



Head, lateral aspect : The face is not visible hi profile 

 and the anteriorly placed ocelli only barely visible. 

 Occiput black with greyish white pollen and a scanty 

 row of long, fine, brownish yellow pile on the lower 

 portion. Beginning at the middle above there are 11 

 short, stout, curved bristles set not far from the eye 

 margin. Proboscis subcylindrical, very slightly com- 

 pressed laterally with a low, dorsal ridge only on the 

 basal third. Palpus extremely short, of one segment. 

 Antenna shorter than the head and slender; first two 

 segments quite short, third long, strongly attenuate 

 from near the base with a slender style as long as the 

 segment. 



Head, anterior aspect : Face below antenna an eight- 

 eenth of head width and strongly divergent below. 

 The face with no pile, very little pubescence, and with 

 1 pair of long, slender, bristly hairs above epistoma 

 and another pair of weaker hairs. Front and vertex 

 only slightly divergent. Vertex deeply excavated. 

 Ocellar protuberance quite small and low with slant- 

 ing sides and without pile or bristles. The anterior 

 eye facets are greatly enlarged but over a very small 

 central medial area. 



Thorax: The mesonotum rather high, strongly 

 abrupt in front but gently convex. It is approxi- 

 mately of the same height and shape as Leptogaster 

 Meigen with the medial portion more prominent and 

 raised into a gently rounded ridge on the anterior as- 

 pect of the mesonotum. Humerus polished and bare, 

 with 2 minute bristly hairs. Mesonotum polished and 

 with almost no pile. There is a scanty row of dorso- 

 central bristles, a small patch of pile in front of the 

 notopleuron, and a wide, greyish white, micropubescent 

 band of pollen from the suture to the humerus. Bris- 

 tles present as follows: 1 very stout, moderately long, 

 black notopleural, 1 still longer, equally stout, supra- 

 alar, none on postalar and 5 pairs of moderately long, 

 stout, black bristles on the scutellar margin. Scutellar 

 disc flattened, micropubescent, with a very few, short 

 setae. Posterior portion of mesonotum gently sloping 

 and not steep as in Psilonyx Aldrich. Color of mesono- 

 tum dark reddish sepia with obscure, wide, black, sub- 

 medial stripes and an obscure posterior medial stripe. 

 The posterior two-fifths of the mesonotum, including 

 the postalar, and laterally to the suture, are all greyish 



