52 DUBHAM DIPTERA. 



VI. 73. 



11 (10). Abdomen with narrow whitish bands on the hind 



margins of the segments. 



12 (13). All tarsi with white rings. 



458. Cricotopus tremulus, L. 

 Escomb, 1 $, 1 ? , 15-6-99. 



13 (12). Only the mid and hind tarsi with white rings. 



14 (15). Thorax yellow with black stripes. (461. motiator, L.) 



15 (14). Thorax black, unstriped, only a little yellow in front. 



465. Cricotopus annulipes, Mg. 

 Very common at Bishop Auckland in spring. 



16 (9). Mid and hind femora nearly all white. 



466. Cricotopus sylvestris, F. 

 Common at Bishop Auckland in spring. 



74. Orthocladius, v.d. Wulp. 



1 (19). Halteres pale. 



2 (6). Large species, at least 4 mm. 



8 (4) (5). Thorax dark green, shining, stripes black. 



(473. olivaceus, Mg.) 



4 (8) (5). Thorax yellow, stripes brown. 



(476. sordidellus, Ztt.) 



5 (8) (4). Thorax yellow, stripes black. (478. notatus, Mg.) 



6 (2). Smaller species, under 4 mm. 



7 (13). Darkish species. 



8 (12). Size 2-3 mm. 



9 (10) (11). Thorax black with two white lines. 



(472. albolineatus, Mg.) 



10 (9) (11). Thorax black with yellow shoulders. 



(477. frigidus, Ztt.) 



11 (9) (10). Thorax yellow with black or chestnut stripes. 



(471. variabilis, Staeg.) 



12 (8). Size 1 mm. (481. minutus, Ztt.) 



13 (7). Pale or yellow species. 



14 (17) (18). Thorax testaceous and striped. 



15 (16). Abdomen green, or brown, with pale faint bands. 



(474. testaceus, Mcq.) 



