1913] 
Burrill: Lake Michigan Swarms of Chironomids 
61 
liar in that it did not hover over the walk but over the south grass 
edge of the walk. Still more remarkable was the position the 
swarm took — quite nearly vertical in a peculiar wall-like forma- 
tion out over the grass edge. At times they arose in the air 
about twelve feet or three and a half meters, but usually remained 
at a four to eight-foot level, or about two meters. Few midges 
came within a foot of the ground. There were thicker nuclei 
here and there as if these smaller swarms had formed the living 
wall. For some acres about, I could find no other swarms on 
other walks or over the lawn except two small ones near the 
walk on Linden Drive and about seventy-five paces from the 
main swarm. A sweep of the net gave only males. Frequently 
a midge left the swarm, soaring higher southward until he came 
to rest in the linden trees. No regular motion of the swarm could 
be unravelled though most of the midges were oriented to a slight 
draft from the south. 
Some of the students helped me watch this swarm, whose sound 
was inaudible to me, and found the individual flights so irregular 
that it was a marvel how the swarm kept so definitely in the 
wall-like formation. The only way to discover the irregularity 
of flight is to keep one’s eyes fixed on some individual silhouetted 
against the sky for as long as possible, since observation of the 
swarm as a whole deceives one into thinking the flight much more 
regular than it is. When one student ran through the wall of 
midges, they swayed out over the walk as if disturbed, but they 
swung back into the wall position without the bounding higher 
already referred to in Schuster’s paper. In another swarm near 
the Dairy power-house, the reverse happened, as they bounded 
up from the sweep of the net. 
By 8 p.m. there were no more midges to catch, the temperature 
fast falling below 60° F. On June 7, following a cold spell, the wall 
became more like an irregular box hedge, 14 feet high (4 meters) 
in places, and on this occasion leaning at an angle of 10° to 15° 
towards the South, whence came a light breeze. It was still cold 
but moderating, thus inhibiting flight by 8 p.m. Caught only 
males again from the swarm east of the Dairy power-house as 
before. 
