44 
Length of dried specimens, 2 1/2—3 mm.; wing, 3 1/2—4 
mm. 
Paratype a male, cotypes 3 males and 8 females, all taken at Al¬ 
gonquin, Ill., by Dr. Wm. A. Nason. 
This species belongs to the venustum group. The males are 
easily recognized by the parallel pollinose stripes, whiter and less 
metallic than those of venustum , and not oblique as in that species 
(Figs. 14 and 18), and by the extent of silvery pollinosity on the 
middle and hind tibiae, not merely a basal ring as in venustum . 
The females differ from those of venustum especially in the form 
of the face (Fig. 13) and in the mesonotal pollinosity with deep 
humeral notches. 
S. venustum Say (Figs. 16-22).—This species and S. vittatum 
are together called “the black-fly" in northern latitudes, where they 
are the northern representatives of meridionale and pecuarum in 
the South. Venustum is the species found so disturbing by Agassiz 
in 1850, as described in his “Lake Superior." “Flies exceedingly 
troublesome,'’ says the narrator, under date of August 12, “rising 
in swarms from the blueberry bushes when we touched them. 
* * Having for the first time open ground enough to observe 
their manceuverings, we tried to outrun them, and easily left them 
behind, but in a short time the swarm, like a pack of wolves, and 
guided to all appearance in like manner by scent, came ranging 
up in a body and fell on afresh."* That conditions in that region 
are still the same is shown by an article in the 12th Report of 
the Michigan Academy of Science (1910)!, which says that mem¬ 
bers of the engineering staff of the University of Michigan were 
— r - - - on Douglas Lake, in Cheboygan county, 
1909; and that the opening of the en- 
1 station were postponed for a week 
ft of these pests. The species here 
. well worked out in New 
ti^de at Mum ford on speci- 
mes, she says, made their 
™he first of April, 
water, and these were 
of the larvae in the 
water and in the 
in the Southern 
