1921.] 103 



A northern species taken sparingly by the late Mr. Verrall at 

 Tongue and Lairg (Sutherland) in June, and at Rydal and Winder- 

 mere (Westmorland) in July. Col. Yerbuiy also caught a male at 

 Lochinver (Sutherland) in July 1911. Mr. H. W. Andrews, how- 

 ever, appears to have taken a single male in the Thames Marshes 

 (Kent) on June 11th, 1910. 



4 (3) Arista only pubescent. Thorax darker in front and with only an 



indistinct central stripe. Hind femora with posteroventral long hairs 



*2. surda Zett. 



S • Resembling litorea, but arista much shorter-haired and fronta 

 orbits narrower. Thorax all dai'ker, especially not so grey in front, 

 slightly shining. Abdominal dark patches less distinct and more 

 variable in outline according to the point of view. Leg bristles as 

 in litorea, but often only one posterodorsal bristle to middle tibiae 

 and hind femora with long fine posteroventral hairs on basal half. 



$ . luterfrontalia less distinct than in litorea and not so produced 

 forward. No very distinct occipital grey patch behind ocellar 

 triangle. Thorax darker and five-, rather than three-striped, slightly 

 shining. Abdominal patches still less distinct. Front tibiae with a 

 bristle behind ; hind femora without the long fine posteroventral 

 hairs of the male, but a few shorter very fine hairs can usually be 

 traced about the base, which are absent in litorea. 

 Length 5-6 mm. 



This species appears to be more widespread than litorea. 

 Mr. Verrall caught it at Tongue (Sutherland) in June on the same 

 day as he took litorea, and Col. Yerbury found it at Aviemore 

 (Inverness) and Mr. A. E. J. Carter at Blairgowrie (Perth) in 

 June. It has also occurred at Martham and South Walsham (Nor- 

 folk) in June and July, and at Ringwood and other localities in the 

 New Forest (Hants) also in June and July. A specimen was taken 

 by the late Mr. A. Piffard on the canal-bank at Boxmoor (Herts) in 

 August 1898. It stood in Kowarz's Collection under the name co7n- 

 puncta Wied. 



5 (2) Frons at narrowest part usually but little wider than third antennal 



joint is deep, never more than twice as wide. 



6 (7) Arista subplumose. Wings very nigrescent 



.... denigrata Mg. (v. species 10). 

 This species, though usually having four pairs of postsutural 

 dorsocentral bristles, may occasionally possess only three pairs ; it is 

 therefore included here. A closely allied species, disparYln., should 

 be found in Britain. It is easily distinguished from denigrata by the 

 presence of a distinct posteroventral bristle on middle tibiae, and the 

 absence of posteroventral long bristles to hind femora. 



7 (6) Arista microscopically pubescent. Wings not conspicuously nigres - 



cent. 



8 (9) Middle tibiae usually with a distinct bristle in front at middle. Front 



tibiae with a bristle behind at about middle. Hind tibiae with two 



* Species marked with an asterisk are additions to Verrall's " List of British Diptera." 



