DURHAM DIPTERA. 183 



XXVIII. 279. 



6 (7). Abdomen nearly all indeterminately orange. 



Py. granditarsa, Forst. (1494) 



7 (6). Abdomen with only one pair of yellow spots placed 



on the third segment. Py. rosarum, F. (1495) 



8 (5). Abdomen with three or four pairs of reddish, 



yellowish, or bluish spots. 



9 (10). Thorax very dull; front mouth edge very much pro- 



duced. PL manicatus, Mg. (1479) 



10 (9). Thorax shining. 



11 (32). Antennae absolutely without yellowish markings 



beneath the base of the third joint. Abdominal 

 spots quadrate (VII. 11). 



12 (15). Abdominal markings bluish quadrate spots, not 



bands. 

 13(14). Fourth pair of abdominal spots visible; shorter 

 species (7 mm.) with a broader head. 



(148 1. PL dtscimanus, Lw.) 

 14(13). Only three pairs of spots visible; longer species 

 (8^ mm.) with average head. 



PL albimanus, F. (1485) 



15 (12). Abdominal markings yellowish. 



16 (29). Hind legs with at least a dark band on the femora 



and tibia?. 



17 (18). Hind legs almost all black. 



(i486. PL podagratus, Ztt.) 



18 (17). Hind legs with conspicuous pale knees, as well as 



the tip of the tibiae, &c. 



19 (22). Face considerably produced at the mouth. 



20 (21). Abdomen nearly linear. (1480. PL tarsalis, Schum.) 



21 (20). Abdomen ovate. (1482. PL melanopsis, Lw.) 



22 (19). Face not much produced at the mouth. 



23 (26). Paler species, with usually only a slight dark ring on 



the hind femora and tibiae. 



24 (25). Larger species (9 mm.). The dust spots on the side 



of the frons golden and well defined. 



PL scambus, Staeg. (1487) 



