204 DURHAM DIPTERA. 



XXVIII. 317. 



317. Sericomyia, Mg. 



1 (2). Abdominal bands dark yellow, and widened at the 



sides ; scutellum blackish. 



1 615. Sericomyia borealis, Fin. 

 The males are common among the heather, but I 

 have never seen a female. " Killingworth and 

 Harnham," C. Robson. 



2 (1). Abdominal bands whitish yellow and narrow at the 



sides ; scutellum reddish. 



16 16. Sericomyia lappona, L. 

 Waskerley, 1 $, 4-6-01. "Killingworth or Harn- 

 ham, one specimen," C. Robson. 



318. Chrysotoxum, Mg. 



1 (4). Third antennal joint nearly as long, or longer than 



the two basal joints together, measured on the 

 inside (III. 46). 



2 (3). Rather large species, 13 mm. Male genitalia large 



and unsymmetrical. ( I 6i7- catitum, Harr.) 



3 (2). Smaller species, 9^- mm. Male genitalia incon- 



spicuous. 



1 7 18. Chrysotoxtim aratahim, L. 

 Hesleden, 2 $, 11, 12-8-99. "Killingworth and 

 Harnham," C. Robson. 



4 (1). Third antennal joint conspicuously shorter than the 



two basal joints together. 



5 (12). Abdomen with four fairly equal "golden bows." 



6 (9). Abdominal bows extending over the side margins; 



wings with no conspicuous dark splash near the 

 costa, after the middle. 



7 (8). Short plump species ; usually the yellow colour 



predominates on the abdomen. 



(1619. octomacidatum, Curt.) 



8 (7). Long elegant species ; usually the black colour on the 



abdomen is conspicuous. (1620. elegans, Lw.) 



