Fluke—Syrphidae of Wisconsin. 
219 
31 
38 
32 
33 
42 
34 
28. Hind femora slender, front of female long, narrowed above; the 
cheeks very narrow below the eyes; abdomen often very 
slender ... Baccha (p. 227) 
Hind femora thickened; front not unusually long in female.... 29 
29. Epistoma produced anteriorly, the face in profile deeply concave 
from antennae to tip; third joint of antennae rounded- 
....Sphegina (p. 238) 
Epistoma produced more downward, in profile gently concave; 
third joint of antennae not rounded- Neoascia (p. 239) 
30. Front long, much narrowed above in the female; cheeks very 
narrow, the eyes approaching each other at the lower third 
of the head, wings usually with dark picture; abdomen 
more or less elongate.. .Ocyptamus (p. 228) 
Flies not having the above described assemblage of characters 
31. Mesonotum with distinct yellow lateral margins. 
Mesonotum not with yellow lateral margins... 
32. Abdomen with definite yellow cross-bands. 
Abdomen not with definite yellow cross-bands. 
33. Hind femora extraordinarily thickened. .Syritta (p. 246) 
Hind femora slender... 
34. iSixth abdominal segment in the male as long as the two preced¬ 
ing together, cylindrical; fifth segment of the female one- 
half as long as the preceding. Eupeodes (p. 232) 
Sixth abdominal segment of the male not peculiar; the fifth 
segment of the female one-third or one-fourth as long as the 
preceding ...... 
35. Front very convex; eyes of male with an area of enlarged facets 
above (Lasiopticus) .*Scaeva 
Front not remarkably convex..... 
36. Third longitudinal vein with distinct curvature into the first 
posterier cell; third joint of antennae elongate oval.... 
.Didea (p. 232) 
Third longitudinal vein straight or gently curved; epistoma 
not produced (if produced snout-like, Rhingia). 
37. Males holoptic. ,Syrphus (p. 232) 
Males broadly dichoptic; arista thickened.... *Chamaesyrphus 
38. Mesonotum with median cinerous line; ocelli usually remote 
from the vertex ... 
Mesonotum not with a median cinereous linear stripe. 
39. Hind femora in the male thickened and arcuate, the tibiae 
dilated at the tip .. Toxomerus (p. 237) 
Hind femora simple and straight; tibae not dilated at the 
tip....... Mesogramma (p. 237) 
40. Eyes of male with an area of enlarged facets above; fourth 
segment of abdomen with two median yellow stripes and 
oblique side spots. Allograpta (p. 235) 
Eyes of male not with an area of enlarged facets above; fourth 
abdominal segment not so marked.... 41 
35 
36 
37 
39 
40 
