DURHAM DIPTERA. 1 89 



XXVIII. 388. 



23 (22). Stigma yellowish ; thorax shining blue-black ; legs 



mostly orange ; base of femora and ring on hind 

 tibiae dark. 



1 5 19. Syrphus viltiger, Ztt. 

 Gibside, 1 $, 22-8-96 ; Shipley, 1 ?, 27-8-98 ; 

 Hesleden, 1 $, 4-8-99, 1 $, 15-8-99; Harperley, 

 1 ?, 4-8-00; Wearhead, 1 ?, 20-8-01. 



24 (19). Face without any distinct black line, at most a 



darkish knob. 



25 (28). Antennae all black ; third joint not paler beneath. 



26 (27). Pubescence on the frons black ; femora black about 



the base. 



1520. Syrphus grossularice, Mg. 

 Gibside, 3 % August, 1896; Hesleden, 11 ?, August, 

 1899 ; Howick, Northumberland, 2 $, August, 

 1905. It is generally considered a somewhat rare 

 species, but it was common at Hesleden in 1899. 



27 (26). Pubescence on the frons yellow ; femora entirely 



yellow. ( J 5 21 ' diaphanus, Ztt.) 



28 (25). Antennae partly yellow, at least beneath the third 



joint. 



29 (32). Thorax dullish ; pubescence on scutellum black. 



30 (31). Large species, 1 1 mm. Female hind femora all 



yellow. Numerous tiny black bristles on the upper 

 tip half of the hind femora in both sexes. 

 1522. Syrphus ribesii, L. 

 Very common everywhere. 



31 (30). Small species, 10 mm. Female hind femora broadly 



black at base, very few tiny black bristles on the 

 upper tip half of hind femora. 



1523. Syrphus vitripennis, Mg. 

 Said to be equally as common as ribesii, but I have 

 not found it so here, although I may possibly have 

 overlooked it. Harperley, 1 $, 27-5-98; Hesleden, 

 3?, 23, 30, 31-8-99, 1 i, 23-8-00; Wearhead, 

 2 1-8-0 1. 



