104 DURHAM DIPTERA. 



XVIII. 



4 (3). Hind femora with a black ring or band. Tarsal joints 



yellow with orange ends and black tips. 



(942. guttiventris, Ztt.) 



5 (2). Foot-pads present (VI. 10), or, if absent, then X.5. 



ends in V.4.b.b. (V. 5). 



6 (19). Third antennal joint with a distinctly two-jointed 



short blunt terminal style. 



166. Dioctria, Mg. 

 Life history unknown. 



7 (8). Pleurae with only a slight glistening streak. 



(945. rheinhardi, W.) 



8 (7). Pleurae with a distinct glistening streak. 



9 (10). All femora, and also the fore tibiae black. 



(945. atricapilla, Mg.) 



10 (9). The fore and mid femora at least yellow. 



11 (12). Wings entirely dark brown or black. 



(943. celandica, L.) 



12 (11). Wings clear. 



13 (18). Abdomen black without yellow bands. 



14 (15). Frontal knob large and prominent. 



946. Dioctria rufifies, Deg. 

 Common near streams. Barnard Castle, Harperley, 

 and Bishop Auckland. 



15 (14). Frontal knob small. 



16 (17). Face white. (948. flavipes, Mg.) 



17 (16). Face yellow. (947- baumhaveri, Mg.) 



18 (13). Abdomen with yellow bands. (949- linearis, F.) 



19 (6). Third antennal joint with an indistinctly two-jointed, 



pointed, terminal style, or with a terminal bristle. 



20 (21). Face without any knob. 



167. Isopogon, Lw. (950. brevirostris, Mg.) 



21 (20). Face with a distinct knob. 



168. Lasiopogon, Lw. (951. cinctus, F.) 



22 (1). 0.2. closed (V. 4). 



23 (26). Third antennal joint without either style or bristle 



(III. 18). 



