146 fJ"iy' 



the fringe of long hairs round the posterior edge of the hypopygium 

 is present in any other British species. The female is not so easy of 

 I'eeognition, and without care might be mistaken for the same sex of 

 pleurnlis. It is, however, a larger insect with a longer costa, but a 

 much surer distinction lies in the very abrupt curve at which the first 

 thin vein comes off, a really good and reliable character. 



Altifrons. — In woods from April to Juno, but by no mciins 

 common. Most likely to be confused with the darker forms of 

 variabilis, from which its high and narrow frons, shorter costa and 

 fringe, and smaller size distinguish it. 



Variabilis. — A large and not uncommon species, with strongly 

 tinted wings and large tibial bristles, occurring in the early summer 

 and again in the autumn. 



Pleuralis. — One of our commonest species, and to be found from 

 spring to late autumn in all sorts of localities. In this group with 

 bristly pleurae and yellow halteres the number of closely allied species 

 is somewhat confusing, but the male of pleuralis may be identified at 

 once by its lar^e and strongly bristled hypopygium, which is totally 

 unlike those of its allies but resembles in a remarkable manner that 

 of humilis, the resemblance extending even to the hairiness (in 

 unrubbed specimens) of the last two or three abdominal segments. 



Dii^ersa. - -Oitew swept up in the net along with pleuralis, but by 

 no means as common as that species. It seems to bear much the same 

 relationship to pleuralis as alticolella does to humilis, in each case the 

 male genitalia affording the essential distinctions. 



Subpleuralis. — Common and widely distributed. Closely allied to 

 the two preceding species, from which the shortened second costal 

 divisions and the characters of the hypopygium, besides other smaller 

 differences, serve to distinguish it. It is probably the pulicaria of 

 Meigen and Becker, but not of Fallen. Mr. Collin, when visiting 

 Paris, was kind enough to examine the Phone in Meigen's Collection. 

 I quote from his letter, " As you surmised, species were hopelessly 

 mixed among the types of the smaller insects, hut pulicaria, Fin., may 

 be limited to a species with pale halteres, costa beyond middle of wing 

 and with long cilia, and mesopleurag hairy, indistinct ciliations to hind 

 tibiae, according to a specimen labelled by Becker in Meigen's Col- 

 lection." Subsequently he wrote, "It was only the pulicaria of 

 Meigen that I saw, and Zetterstedt, who had seen Fallen's type, was 

 doubtful if Meigen's pulicaria was the same as Fallen's. According to 

 Zetterstedt, pulicaria has the costa slightly longer than in rufipes, i.e.. 



