64 Bulletin Wisconsin Natural History Society [Vol. 11, Nos. 1-2 
burg (1883, Die Insekten nach ihrem Schaden und Nutzen. Leip- 
zig u. Prague, p. 232, Die Chironomidae oder Zuckmiicken) de- 
scribed a swarm which flew from 4 to 9 p.m. I have described in 
a recent paper a late summer swarm of C. plumosus which flew 
till after midnight. Related forms must vary similarly since Ain- 
slee (1907, Jan. Notes on the Swarming of a Species of Crane 
Fly ( Trichocera bimaculata)) noted some crane flies swarming from 
sunset until over an hour later, when they seemed to be dancing 
in perhaps larger numbers at a temperature of 45° F. This was 
November 2, 1906, by the Potomac River, Washington, D. C. 
At Madison in 1912, the flight was over by 8:30 p.m., May 29; 
by 8 p.m., May 30; was in a sporadic shape at 7 p.m. on the colder 
days of June 2, 3, 5 and 6; and was over by 8 p.m.; June 4 and 
7, the latter two days being times of large swarms. The real 
controlling factor will probably reveal itself when some observer 
studies the dew-point temperature or the minimum temperature 
at which flight is tolerable. If any observer shall seek further 
along this line of argument, and cares to correlate with my notes, 
he can procure complete weather records for my observation per- 
iod from the Government Weather Bureau Station at Milwaukee, 
only 6 miles away, or at the University weather station (for 1912), 
only one-eighth mile away. Although offered their complete rec- 
ords, I have purposely refrained from encumbering the paper 
with more than brief summaries of weather changes, since I enter- 
tain the theory that midges react more to localized influences or 
stimuli. For the same reason I have omitted complete lists of 
insects caught. 
ANNUAL OCCURRENCE 
Taschenberg (ib. p. 233) notes that in dry years midge swarms 
almost disappear. 1910 and 1912 were wet Mays in Wisconsin. 
I have noted that the statements of residents about Lake Winne- 
bago, Wis., indicate that midges are quite inconspicuous in some 
years (: recent paper on C. plumosus Burrill, q. v.). Swarms of 
plumosus seldom last over a week, but of the little black midge 
most commonly noted in these observations, the period extended 
over a month. Further deductions on annual duration are hardly 
safe because of insufficient data at present. 
