200 DURHAM DIPTERA. 



XXVIII. 302. 



5 (6). Hind tibiae with only the basal third orange. 



(1580. hybridus, Lw.) 



6 (5). Hind tibiae with the basal two-thirds orange. 



1 58 1. Helophilus penduhis, L. 

 Gibside, 1 $, 1896; Hesleden, 3 $, 2 ?, August, 

 1898-99; Wearhead, 1 ?, 21-8-00. ''Killing- 

 worth," C. Robson. 



7 (2). Antennae bright orange red; abdomen by no means 



transparent; moderately large species, 10 mm. 



8 (9). Paler species ; male with a remarkable tuft of hairs 



on a produced wart beneath the base of the hind 

 femora; back of the head with long black hairs 

 overhanging the eyes. (1582. fruteorum, F.) 



9 (8). Darker species ; male with only an inconspicuous 



tuft; back of the head without any long black 

 hairs overhanging the eyes. (1583. versicolor, F.) 



10 (1). Abdomen linear; species generally rather small, 9 mm. 



11 (16). Third antennal joint normal; abdomen with con- 



spicuous lunules ; face produced. 



12 (15). Upper mouth edge produced, but blunt at its tip. 



13(14). Abdominal markings moderately lunulate; back of 

 the head without any dark streak behind each 

 eye. (1584. hinulatus, Mg.) 



14 (13). Abdominal lunules very much bent; back of the head 



with a dark streak behind each eye. 



(1585. transfugus, L.) 



15 (12). Upper mouth edge extremely produced and pointed 



at its tip. (!586. lineatus, F.) 



16 (11). Third antennal joint angulated about its tip on the 



upper side ; abdomen with longitudinal markings ; 

 face scarcely at all produced ; long and narrow, 

 12 mm. (15S7. vittatus, Mg.) 



