Fluke—Syrphidae of Wisconsin. 229 
Platychirus St. Fargeau and Serville 
(Table of males, adapted from Yerrall) 
1. Front tibiae abruptly dilated at the extreme tip, the basal joint 
of front tarsi exceedingly larger than the other joints, 
front femora with a remarkably coarse ciliation behind on 
almost the whole length, antennae pale beneath the third 
joint ... peltatus 
Front tibiae gradually dilated or dilated soon after the base, 
antennae nearly all black. 2 
2. Front femora with a row of isolated long black hairs behind.. 3 
Front femora without a row of isolated long black hairs behind 4 
3. Front femora with a peculiar long white hair at the base, and 
with about six isolated black hairs behind; front tibiae 
with no kink above; longitudinal and black cross^bands 
of abdomen very narrow . immarginatus 
Front femora without a peculiar long white hair at the base, 
and with about five isolated black hairs behind; front 
tibiae with a kink above; black cross-bands and longi¬ 
tudinal stripe of abdomen broader. scambus 
4. Abdomen with four pairs of abdominal spots. 5 
Abdomen with three pairs of abdominal spots. 7 
5. Front tibiae only slightly dilated, and with the outer angle 
below sharp and very little produced downward; front 
femora without a peculiar long white hair at the base.... 
.. species? 
Front tibiae considerably dilated, and with the outer angle 
below more rounded and produced downward, front femora 
with a peculiar long white hair at the base. 6 
6. Middle femora at the base with a bunch of long dense pile, ab¬ 
domen with a distinct median longitudinal black stripe.. 
. quadratics 
Middle femora at the base without such bunch of long dense 
pile; abdomen with scarcely any black, the median longi¬ 
tudinal stripe being nearly obsolete. perpallidus 
7. Front femora with a few weak black hairs behind; basal ab¬ 
dominal spots small, nearly circular; wings brownish; 
small rather dark species. .hyperboreus 
Hairs behind on front femora mostly yellow, basal abdominal 
spots usually more nearly the size of the second pair; wings 
nearly hyaline; small, narrow, more yellowish spe¬ 
cies . angustatus 
