130 MOSQUITOES OF NORTH AMERICA 
where they, especially towards evening, flock together in dancing swarms and 
tempt the females to come up by the noise of their wing-beats. 
“When a female comes up into this dancing cloud it is chosen by a male and 
the two separate themselves from the rest, while the male swarm continues the 
dancing with uninterrupted music at varying heights in the air.” 
The swarming of Aédes spencerit has also been observed by Knab, on the Sas- 
katchewan prairies. This is described in Smithsonian Miscellaneous Collec- 
tions, volume 50, part 4, pages 542-544. 
“ Adults of this species first appeared active on May 30 and a few came to 
bite. They were first noted in numbers on June 5, a warm, sunny day follow- 
ing four days of cold, cloudy weather. They came drifting before the wind, and 
during calm intervals were very annoying. At 10.45 a. m., on a rise of ground 
west of the town, the highest rise on that part of the prairie, a swarm of about 
50 males gathered above my head. They emitted a high-keyed piping sound, 
swinging backward and forward and swaying sidewise, all the time facing the 
wind. With every gust of wind they were scattered toward the ground, only to 
reassemble when the wind decreased. When I passed the place again, at 12.45 
p. m., the males were still in evidence, although much interfered with by the 
wind. The same day, at 5.30 p. m., another swarm of males was observed in the 
upper part of a ravine, where the slopes were gentle. They were going through 
rapid evolutions, darting forward and upward and dropping back again, but 
without unison. When disturbed by the wind their flight became more rapid, 
and sudden gusts caused them to fly to the ground. Several pairs were seen 
flying off in copula, and once the female was observed approaching the swarm 
from beneath. There was a second swarm of males farther down the ravine, 
about half way up the slope, and, like the other, at the margin of the shrubbery 
filling the bottom of the ravine. In this case a swarm of very small Chironomids 
was mixed with the lower part of the swarm. In crossing an open field in the 
river valley at 6.30 p.m. a swarm of males formed over my head and, following 
me, increased to the number of perhaps two hundred. They disappeared when 
I approached the woods on the edge of aravine. This experience was repeated in 
the field beyond, and upon nearing the edge of the woods the swarm again de- 
parted and could be seen in the middle of the field. Several days of cold and 
cloudy weather followed, during which the mosquitoes remained quiescent. 
After the heavy rain of the previous night, the afternoon of June 9 was warm 
and sunny and the mosquitoes exceedingly abundant and active. At 6.30 p. m. 
I walked toward the river with a companion. As soon as we had left the town 
the female mosquitoes began to rise out of the grass and alight upon us. There 
was a brisk breeze blowing and the mosquitoes settled on the leeward side of our 
bodies, and a cloud of them followed us, keeping for the most part about our legs. 
These clouds increased rapidly and became very aggressive as we passed down 
into the valley, where we came upon a cloud of males on the open prairie. When 
we approached them they formed in two swarms over our heads. My companion, 
being the bulkier man, attracted a much larger swarm. We thus each had two 
swarms of mosquitoes about us; the one, of females, kept about the lower part of 
our bodies, while the other one, of males, kept above our heads. Several copula- 
tions were noted. Upon entering a ravine the males all left us and only a part of 
the females followed. Upon emerging on the other side of the ravine a new 
swarm of females quickly gathered, and shortly we came upon another large 
swarm of males, which again concentrated above our heads in separate swarms. 
It was now 7 o’clock, but still bright daylight at this season of the year. The 
swarms of males I judged to contain many hundreds, if not a thousand, indi- 
viduals. These swarms, in close formation, followed us up the long hill and 
