September, 1910.1 197 



39 (34) Halteres yellow. 



40 (43) Hypopygium with one or more conspicuoiis bristles on each side. 



41 (42) First costal division more than double the two others. Not a very minute 



species (1 mm. or more). 

 S 9 . An indoor form of preceding species, differing only in its smaller size 

 and yellow halteres, and sometimes in having a more distinctly pale 

 thorax 1 — 1^ mm. halterata, n. sp. 



42 (41) First costal division not double the other two (about If). A very minute 



species (^ mm. or less). 



t^ 9 . Not unlike preceding species in some respects, bnt mvich smaller and 

 paler : — Thorax from reddish-yellow to dusky red, abdomen black ( ^ ) 

 reddish-grey or brown ( 9 ) ; frons dark grey, sitpra-antennal bristles as in 

 halterata, antennae small and yellow ; wings yellowish, costa less than 

 f wing length, fringe moderately long, 2nd thick vein not incrassated nor 

 its outer branch turned tip abruptly, angle at fork moderate, 1st thin vein 

 not recurved at margin ; legs pale yellow, fore tarsi somewhat short and 

 thick, the metatarsi shorter than the two following joints, tip of hind 

 femora blackish, tibial cilia fine and indistinct ; in the only male before 

 me (taken in cop.) the hypopygium has apparently but a single strong 

 bristle on each side, the ventral plate is small and inconspicuous, the 

 subanal body very large, and the anal organ small and yellow... 



barely -J- mm. niinutissima, n. sp. 



43 (40) Hypopygium without bristles. 



S 9 ■ In size and appearance very like simplex ; but apart from the bare 

 mesopleurse, it differs in having a broader frons, smaller supra-antennal 

 bristles (the tmder pair being almost minute), and a longer and finer 

 arista ; the costa too is longer — | wing length ( J ) and rather more ( 9 ). 

 the fringe only moderately long, the legs yellowish-brown rather than black, 

 the tibial cUia more distinct and the seam deflected outwards a little below 

 the middle instead of being continued straight as in simplex... 



1 — If mm. exigua, n. sp. 



Fasciata, Fall. — A widely distributed species. The male seems 

 to be seldom met with, but the female is not uncommon. On one 

 occasion I came across a swarm (apparently all females) hovering at 

 the roots of an old and half decayed ash tree. Although coming 

 under this Section, it looks out of place among its associates, and 

 bears a much closer resemblance to the meigeni group in Section B, 

 agreeing with it in its yellow colouring, short costal fringe, doubly 

 ciliated tibiae, and in type of hypopygimn — ;characters, especially the 

 last two, which would, I think, justify their inclusion in a separate 

 genus. The relationship to the meijeni group is further shown in 

 that the anterior scutellar bristle is often represented in the female 

 fasciata by a large and coarse hair. 



