SWARMING OF ANOPHELES 127 
regarding the mating habits in the genus Anopheles, the following notes are 
offered. Much to his surprise the writer found that the males of Anopheles 
iota as do those of Culex, although the behavior in the two forms is quite dif- 
erent. 
“The observations were made on Plummers Island (Maryland) in the 
Potomac River, about ten miles above Washington. Near the highest part of 
the island is a ledge of rock forming an open space surrounded by the woods on 
three sides. The side towards the river is open, save for a couple of small trees 
at the edge, and terminates in a nearly perpendicular cliff. On October 7, 
shortly before 5 o’clock, the writer visited the spot to enjoy the sun-set. The 
ledge is about sixty feet above the water and on its highest part, where some tufts 
of tall grass grow in a crevice of the rock, was a swarm of dancing Diptera. The 
swarm was directly over the tufts of grass, its base seven or eight feet from the 
ground, the apex five or six feet higher. Although in appearance and action 
quite unlike Culex pipiens (observed on previous occasions) they were recognized 
as mosquitoes by the prominent palpi and the plumed antennz. With a sweep 
of the net fifteen were secured and proved to be males of Anopheles punctipennis. 
Their appearance in flight differed from pipiens mainly by the position of the 
legs which were held straight behind and close together. The palpi and antenna, 
directed straight forward, also appeared much more prominent than in pipiens, 
which, together with the much longer legs, extending out behind, gave them a 
very characteristic appearance. 
“ Tn their actions, too, they differed markedly from pipiens. The swarm was 
small, composed of less than a hundred individuals, and was not as compact as 
the swarms of pipiens. The movements of these males were far more free and 
varied than those of pipiens which constantly repeat the same circumscribed 
movements. The Anopheles flew about in the swarm in a circling upward or 
downward ‘ corkscrew ’ course. Their movements were more rapid than those of 
pipiens and often irregular; single individuals would at times leave the swarm, 
and cutting a wide circle, return into it. Sometimes these stray individuals 
would fly for a short distance with a peculiar rapid zig zag motion—a series of 
short sidewise jerks—and then return with the ordinary steady flight. In spite 
of these varied evolutions the mosquitoes showed a tendency to face in one 
direction, presumably towards the wind, although the evening was perfectly calm 
and there was no breeze apparent. As it began to darken the males began to 
leave the swarm one by one, flying upward, either into surrounding trees or more 
often they would disappear into the sky. On this evening copulation was not 
observed and from the following observations it may be assumed that union only 
takes place during the early part of the swarming. 
“ Although stormy and cold weather intervened, the following Sunday proved 
fine and the ledge on the island was again visited. Shortly before 5 o’clock, 
with the sun still shining but near the horizon, a few males were found already 
assembled and engaged in their circling flight above the grass-tufts. Others 
came from different directions and joined the swarm and by sunset it consisted 
of perhaps sixty or seventy mosquitoes. It was difficult to follow the movements 
of single mosquitoes but it seemed that in circling about they described a figure- 
of-eight—sometimes on a plane, or ascending and descending. At 5.15 a pair 
was seen falling out of the middle of the swarm, grappling each other as they 
fell. They had not dropped far below the swarm when union was effected, and, 
swinging out in opposite directions, still united they drifted slowly away towards 
the ground. Within ten minutes six pairs were seen to drop out of the swarm 
and copulate in this manner but after that no more. Three of the pairs were 
captured in the net; one pair tested in the bottom of the net about a minute, 
then separated and flew out; the other two pairs remained united even after 
