1912.] 



99 



Breviseta, n. sp. 



S. Thorax and abdomen black; frons broad, nearly f as wide again as 

 long, dnll and black ; supra-antennal bristles small and approximated the 

 under pan- half the size of the upper,- antennae large, as in alHcans ; arista 

 short and only a little longer than the length of the frons measured up the 

 middle; palpi yellow and with the ordinary ciliation; wings clear, costa not 

 quite reaching wing middle, fringe only moderately long, 1 equal to 2 + 3 

 angle at fork rather large ; legs brownish black, hind femora with moderately 

 long hairs beneath, hind tibiae stout, well arched and with strong bristles • hypo- 

 pygium small and unarmed ; anal organ small and yellowish. Length If mm. 

 By the table it runs down to the neighbourhood of albicans 

 and rata, having bare pleura, yellow halteres, and bristly hind tibis. 

 From both it may be known by the complete absence 'of any pale 

 dustmg on thorax or abdomen; by the large and equal scutellar 

 bnstles (m the other two the anterior bristle in the male is never more 

 than half the size of the posterior one, and often considerably less) • 

 by the angle made by the forking of the 2nd thick vein being fairly 

 large instead of acute ; by the dark, almost black, legs ; and kstly by 

 the short, arista (in rata the arista is full long, but in albicans, with its 

 large antennae, it is only moderately long, yet distinctly longer than in 

 breviseta. 



From emarginata, which also has a short arista, the form of the 

 anal organ is alone sufficient to distinguish it. In breviseta the organ 

 IS of the usual cyHndrical form, but in emarginata it is remarkably 

 flattened, lateraUy, so that it is very narrow from side to side and 

 very deep from above downwards. So unique is the shape that it 

 might weU be supposed due to some extraneous cause, were it not that 

 there are three specimens before me, all with the part precisely similar. 

 Further, the legs are much darker (black) in breviseta, and the tibial 

 ciha stronger; the arista also is longer, being somewhat longer than 

 the frons, whereas in emarginata it is only as long as the frons, besides 

 some other small differences. 



A single male taken at Mainswood, 29/6/11. 



Paludosa. At the time of describing this species I had to confess 

 that I did not know the female. This was the more remarkable, as I 

 could at any time sweep up the male in suitable places, and I must 

 have examined scores only to find them invariably males. EventuaUy 

 my perseverance was rewarded, and on the 3rd of September, 1910, 

 I did at lengt,h sweep up a female at Devereux Pool. It agrees so' 

 weU with the male that no special remarks are needed. 



{To he continued.) 



I 2 



