1. PACHYG ASTER 65 



of the world, but only one genus {Pachyg aster) is known in Europe 

 and North America. The metamorphoses of many species of Pachy- 

 gaster are well known and are mentioned under each species ; the larvae 

 live in debris under the bark of decaying trees, where they probably 

 feed on the frass of wood-boring Coleoptera. The perfect insects are very 

 sluggish, but may occasionally be found flying in large numbers. 



One European genus. 1. Pachygaster. 



1. PACHYGASTER. 



Pachygaster Meigen, Illig. Mag., ii., 266 (1803). 



Small squat almost bare flies, with a short ovate abdomen. 

 More or less shining black, but with the tibiae and tarsi always 

 mainly pale yellow. 



Head flattened beneath, and consequently .sliort and flat when viewed from 

 in front. Proboscis short and partly withdrawn, but with fairly large sucker- 

 flaps ; iialpi small and inconspiciious. Eyes practically bare, usually touching on 

 the frons in the male (but not in P. orbitalis) but widely separated in the female, 

 very large in both sexes. Antennas short, placed just below the middle of the 

 head when seen in profile ; third joint enlarged, orbicidar, with four slight 

 annulations and a long subterminal arista ; arista usually bearing a very short 

 dense pubescence which has the effect of making it appear thickened except at the 

 extreme tip. 



Thorax proportionately long, slightly broadened l)el)ind, arched, and with a deep 

 transverse suture which is V-sliaped at the middle, while outside and behind the V the 

 disc of tlie thorax is inflated. Pubescence on the disc sliort and rather inconspicuous 

 even though dense. Scutellum long and rather triangular, with a shallow transverse 

 channel before its tip, and without any marginal spines, but extending far beyond 

 the mesonotum. 



Abdomen very short, broader than long and broader than the thorax, ovate and 

 strongly arched, with five obvious segments. Genitalia narrow and usually con- 

 cealed. 



Legs simple ; femora longer than the tibiae ; basal joint of all the tarsi nearly as 

 long as the other four joints together. Pubescence very slight. 



Wings (figs. 91, 94) with a venation rather like that of Beris, but the cubital vein 

 is much shorter and the apparently pentagonal discal cell rests for a much longer 

 space (in fact for about half its length) on the upper branch of the postical vein ; 

 discal cell emitting only two veinlets to the margin from its upper part, because the 

 lower (apparently third) veinlet is really a continuation of the upper branch of the 

 postical vein while tJie normal thiixl veinlet is absolutely missing; cubital vein 

 usually distinctly forked (but not in P. minutissima, fig. 91); discal vein very faint 

 or even imperceptible on its basal part up to the beginning of the discal cell, and 

 its primary upward and downward fork forms an almost flat base to tlie discal cell ; 

 lower branch of the postical vein united to the anal vein well before the wing- 

 margin, and thereby causing the anal cell to be closed and with a long pedicil. 



This genus is the only one of the subfamily which is known to occur 

 in Europe, and is well distinguished from all others (if Neopachyg aster be 

 considered a synonym) by its antennae being placed at about (or but little 

 below) the middle of the head when viewed in profile, and by its short 

 orbicular third antennal joint which bears an almost (though not quite) 

 apical long thin almost bare arista, and by its unarmed scutellum. 



Pachygaster is recorded from almost all Europe (but not by Bonsdorff 

 from Finland), ISTorth America, and Asia (including New Guinea), and 

 according to Austen is represented in the British Museum by a specimen 



E 



