32 
especially on the Illinois River at Havana. Submitted to Prof. 
O. A. Johannsen, of Orono, Me., the leading authority on the 
species of this genus in America, it was pronounced new and un¬ 
described. It first came to our notice thru dredgings made from 
the Illinois River at Havana March 25, 1895, appearing in large 
numbers in a collection made with a naturalist’s dredge from the 
bottom of the river near the west shore, in the neighborhood of 
an old railroad bridge. Larvae were found at the'same station 
March 31 and April 8; and both larvae and pupae were taken 
here, and also at Stony Creek, Vermilion county, April 8 and 20. 
Adults were collected at Havana from April 19 to 25, 1910 (be¬ 
ing especially abundant on the 22d), and again June 14; and 
finally a single specimen was caught at the same place October 1. 
April 22 was a windy day, and the flies were assembled on drift¬ 
wood in a swarm; and others were floating on the surface in a 
dense layer covering a small area protected by surrounding logs. 
The dates for the adult show that this is a several-brooded species. 
The following description of S. johannseni is by Mr. C. A. 
Hart. 
Male. —Slaty-black, invested with silvery white hair, rather 
long on the abdomen, becoming blackish on the anterior coxse, the 
second palpal joint, and the posterior face of the fore femora, 
moderately dense on the mesonotum and legs. Eyes contiguous, 
the lower halves sharply differentiated as usual, their facets hardly 
1/3 the diameter of those of the upper halves. Antennae and palpi 
black, antennae with minute silvery pubescence. 
Mesonotum with rather dense short silvery pubescence, that on 
disk with a faint golden tint. In certain lights three longitudinal dark 
lines are traceable—a pair distant about one-third the width of the 
mesonotum, curved broadly outward near middle, and a median line 
between them. Scutellum with longer hairs directed medially; 
metanotum lustrous, slightly brownish, with microscopic pubescence. 
Abdomen with somewhat sparse silvery pubescence, longer ante¬ 
riorly, especially on the sides of the first segment. Legs with silvery 
white pubescence arising from minute black points, the hairs in some 
lights slightly fuscous, and distinctly blackish on the posterior side 
of the fore femora. Surface beneath the pubescence yellowish fus¬ 
cous; cox?e mostly black; tips of femora, basal and apical thirds of 
fore tibioe and basal and apical fourths of middle and hind tibire 
black, the lines of separation sharply defined, the dark ends on the 
tibioe connected by a dark line along the extensor surface; tarsi 
black, the base of the fore metatarsus sometimes, the basal half 
of the middle metatarsus, all but the extreme base and apex of the 
hind metatarsus, and often more or less of the second segment 
