352 DURHAM DIPTERA. 



XLIX. 598. 



598. Discocerina, Mcq. 



1 (8). Face with only a single row of bristles near the cheeks. 



2 (3). Cheek with a row of 5-6 very fine bristles, in addition 



to the facial bristles. ( 2 593- obscurella, Fin.) 



3 (2). Cheeks without any fine bristles. 



4 (7). Third antennal joint entirely black. 



5 (6). C 2 not more than half as long again as C 3 ; dorsum 



dark grey-brown, matt; 15— 2 mm. 



(2596. pulicaria, Hal.) 



6 (5). C 2 twice as long as C 3 ; dorsum shining olive-brown ; 



3 mm. (plumosa, Fin.) 



7 (4). Third antennal joint reddish brown. 



(2595. calceata, Mg. = 2594. nigrina, Stnh.) 



8 (1). Facial bristles in two rows. 



9 (10). Antennae entirely black ; face with 3-4 bristles in a 



row near the cheeks and a single bristle in a 

 second row. (glaucella, Stnh.) 



10 (9). Antennae orange ; face with two strong bristles in an 

 inner row and 3-6 weaker in an outer row. 



(xanthocera, Lw.) 



602. Hydrellia, Dsv. 



1 (12). Face white or grey. 



2 (5). Palpi black. 



3 (4). Dorsum dark olive or yellowish grey with darker 



stripes in certain lights. (2601. thoracica, Hal.) 



4 (3). Dorsum shining black, unstriped ; V.2, short, bent up 



at its end. (2600. albi'Iabris, Mg.) 



5 (2). Palpi orange. 



6 (7). Wings dusky. (2613. albicefis, Mg.) 



7 (6). Wings clear. 



8 (9). Small dark grey species, 1-1^- mm. 



(2604. discolor, Stnh.) 



9 (8). Larger species, 2-2J mm. 



10(11). Legs with all tarsi, the fore and mid tibiae and the 



tip of the hind tibiae tawny. 



(2605. hydrocotyles, Hal.) 



