390 DURHAM DIPTERA. 



LVII. 663. 



69 (69a). Ocellar knob broad, two-thirds of frons; V.4. strongly 



bent at the base. 



2856. Phora incrassata, Mg. 

 Hesleden, 1 $, August, 1899. 



69a (69). Ocellar knob narrow, half of frons ; V.4. only slightly 

 bent at the base. (2857. carinifrons, Ztt.) 



70 (66). No ocellar knob on the vertex. 



71 (72). V.3. with distinct bristles at its base ; V.4. strongly 



bent at its base ; palpi yellow, (jnordellaria, Fin.) 



72 (71). V.3. without bristles, or its whole length bearing fine 



micro-hairs. 



73 (74) (77). V.4. strongly bent at its base ; whole length of 



V.3. fine haired. {femorata, Mg.) 



74 (73) (77). V.4. at its base only slightly bent, then straight. 



75 (76). Last fore tarsal joint much dilated ; the back of the 



vertex standing up like a half disc on edge, very 

 prominent in the male, rudimentary in the female. 



(co7'o?mta, Beck.) 



76 (75). Last fore tarsal joint not dilated ; vertical hind margin 



normal. (agilis, Mg.) 



77 (73) (74). V.4. gently bent through its whole length. 



78 (79). V.3. straight; hind tibiae with two outer bristles. 



{vitripennis, Mg.) 



79 (78). V.3. distinctly bent and thickened ; hind tibiae without 



outer bristles. -{citreiformis, Beck.) 



80 (1). Frons with an indented centre line; the 2-4 post- 



antennal bristles directed forward and downward ; 

 tibiae without long isolated bristles, at most ciliated. 



81 (84). V.3. not forked. 



82 (83). Four scutellar bristles ; palpi and halteres brown. 



{exemta, Beck.) 



83 (82). Two scutellar bristles ; palpi and halteres yellow. 



(2859. formicarum, Verr.) 



84 (81). V.3. forked. 



85 (101). Thorax entirely yellow or orange. 



86 (89). Costa about one-third of the wing length. 



