DURHAM DIPTERA. 301 



XXXIV. 489, 



23 (20). Fore femora without the stiff bristles on the inner 



side. 



24 (25). The extreme base of the hind femora, the tip quarter 



of all femora, all tibiae, and the fore and mid 

 metatarsi yellow. (mensurata, Beck., $) 



25 (24). Femora black except the extreme base and tip ; tibiae 



and tarsi all orange except the end joints of the 

 tarsi and the tip of the hind tibiae in the female. 



(inermis, Beck.) 



26 (19). The extreme base of all femora black ; inner side of 



the fore femora with black bristles. 



27 (28). Mid and hind legs all black. {nigrifrontata, Beck.) 



28 (27). Mid and hind legs not all black, at least the tibiae 



orange or red-brown. 



29 (80). Femora broadly orange at their tips, (armillata, Ztt.) 



30 (29). Femora only orange at their extreme tips. 



31 (32). Frons protruding ; arista but little thickened, kneed ; 



fore tibiae orange. (nutans, Beck., $) 



32 (31). Frons not protruding; basal half of arista much 



thickened, not kneed ; all tibiae orange. 

 2209. Amaurosoma tibiella, Ztt. 

 Bishop Auckland, 1 $, May, 1901. 



490. Norellia, Dsv. 



1 (14). Arista plumose. 



2 (3). Femora black ; small grey-brown species without 



dorsal stripes ; tip of the wing slightly clouded. 



(femoralis, Lw.) 



3 (2). Femora all orange, or at most with dark dashes. 



4 (9). Dorsum chiefly grey or grey-brown dusted. 



5 (6). Veins of the wing thick and bordered with brown; 



four distinct dorso-central bristles; anus of the 

 male yellow and black ; lamellae always black. 



(nervosa, Mg.) 



6 (5). Veins of the usual strength, not dark brown and not 



brown bordered ; five dorso-central bristles. 



