Couplet 21 (18)
Hind femora each with a dorsal flange of long yellow hairs, reaching
from near base to about three-fourths way to apex; apices or "knees"
entirely black haired; abdominal tergite 4 with yellow hairs
restricted to thin band along anterior margin; a moderately large
(22-27 mm long) fly restricted to Florida . . . . .
Hind femora with black hairs dorsally; apices or "knees" with
a few, scattered very inconspicuous yellow hairs, which cannot
be seen without using a dissecting microscope at over 40X;
abdominal tergite 4 covered with yellow hair, except for a few
black hairs and bristles at the extreme lateral margins; a
medium-sized (15-20 mm long) fly found from the Lake states to
Vermont and North into southern Canada . . . . .