150 DURHAM DIPTERA. 



XXIV. 233. 

 9 (10). Fore coxae yellow ; third antennal joint twice as long 

 as broad ; frons silvered. 



1280. Argyra argentina, Mg. 

 Belburn, 1 &, July, 1897; Wearhead, 1 $, August, 

 1901. 



10 (9). Fore coxae grey ; third antennal joint at most one- 



and-a-half times as long as broad. 



11 (12). Frons silvered, only the vertical triangle black ; 



dorsum broadly and brightly silvered. 



(128 1. argyria, Mg.) 



12 (11). Frons black, only silvered at the eye margins ; 



dorsum with only a very faint white shimmer. 



(1282. leucocephala, Mg.) 



237. Porphyrops, Mg. 



1 (2). Arista with a leaf-like knob at the end. 



(1287. antennata, Carl.) 



2 (1). Arista not knobbed. 



3 (14). Male mid coxae with a strong black apical spine. 



4 (7). Face black; hind femora without any praeapical 



bristle. 



5 (6). Outer anal lamellae of male forked ; fore metatarsi thin 



and as long as the next four joints together. 



(1288. spinicoxa, Lw.) 



6 (6). Outer anal lamellae simple; fore metatarsi thin, but 



not longer than the next three joints together. 



(1289. fascipes, Mg.) 



7 (4). Face white ; hind femora with at least one praeapical 



bristle. 



8 (9). Last abdominal segment purplish ; thorax brilliant 



green ; hind femora with two or more praeapical 

 bristles; legs yellow. (1296. elegantula, Mg.) 



9 (8). Last abdominal segment same colour as others ; hind 



femora with one praeapical bristle. 

 10 (11). Third antennal joint longer than the arista ; legs 

 black ; fore metatarsi not club-shaped. 



(1290. nenwrum, Mg.) 



