14. LEPTOG ASTER 749 



from its position Osten Sackcn called it an intra-alar bristle ; faint traces exist of 

 dorso-ccntral bristles and of the metaplenral fan. 



Abdomen very elongate and very slender, almost without pubescence or bristles 

 except as usual along the sides of the hindmargin of the basal segment. Genitalia 

 of the male rather "well developed • ovipositor ending bluntly. 



Legs long and rather thin, tlie hind pair longest, and the hind femora and 

 tibia) more or less clavate. Pubescence absent, and any bristles very inconsi)icuous ; 

 there are however a few subapical bristles on the posterior femora and the usual 

 postero-ventral bristly hairs on the anterior tibiie, besides the usual terminal tibial 

 spurs and the usual circlet at the tip of each tarsal joint except the last. Claws 

 remarkably long (fig. 404) and not much curved ; pulvilli absent or minute, but the 

 empodium developed like a strong but shorter middle claw. 



Wings with a venation distinguished by the long and narroAv cubital fork-cell 

 and posterior cells, and by the almost parallel-sided open anal cell ; the shape of the 

 discal cell is also peculiar because the upper veinlet is emitted long before the end 

 of the cell, and consequently the seco)id posterior' cell is unusually long and pointed at 

 its base ; small cross-vein absent or present, even in different individuals of the same 

 species. Squamae small and bare. 



The Lcptngastrince as now restricted bear a similar relationship to the 

 rest of the Asilida: as the Systropince do to the Bomhylidw, but with more 

 numerous connecting forms. The two last characters given in the 

 diagnosis must be taken together in order to separate the subfamily from 

 the rest of the Dasypocjonince, many of the latter having very elongate 

 claws and abortive pulvilli but at the same time the alula well (or fairly 

 well) developed, while others have the alula and hind-angle obsolete but 

 the claws and pulvilli normal. In cases of doubt the Leptogastrince can 

 be further distinguished by the rather long antennal style, the limited 

 chsetotaxy (almost but not quite paralleled in Stenobasis, etc.), and the 

 peculiarly pointed base of the long narrow second posterior cell. 



Leptogastcr is the only Palsearctic genus of this subfamily. 



14. LEPTOGASTER. 



Leptogaster Meigen, Illig. Mag., ii., 269 (1803). 



Exceedingly lanky almost bare flies of moderate size and of 

 greyish yellow or blackish grey colour, with short wings and 

 very much elongated hind legs. 



Head widely transverse, wider than the thorax ; face and f rons narrow near the 

 antennae but the face considerably widening downwards and the frons upwards ; no 

 facial knob, but the front mouth-edge slightly produced and bearing a thin mouth- 

 beard ; chin and jowls almost bare ; lower part of the back of the 

 head with a thin postocular ciliation, but the upper part with a 

 row of strong postocular bristles ( = the festoon) ; irons triangular, 

 sunk between the eyes and practically bare, but with faint traces 

 of bristles on the orbits ; ocelli on a bare elevated knob ; collar 

 short and bare. Proboscis fairly long, extending out horizontally ; 

 palpi short and thin, one-jointed. Eyes curved on the inner margin 

 so that they become rather approximate near the antennae. An- 

 tennae (fig. 402) closely approximate at the base, not so long —rt 

 (without the style) as the head ; two basal joints almost equally cyiindHca sf °^zi^ 

 short, and bearing minute bristles ; third joint elongate, long-oval 

 but tapering almost to a point, twice- as long as the two basal joints together, 

 compressed laterally, and bearing a moderately thick {i.e., too thick to be aristiform) 



