122 MOSQUITOES OF NORTH AMERICA 



the plumed antennae of the males to be clearly distinguished and it appeared that 

 the swarm was composed wholly of males. Once a female was seen to dash into 

 the midst of the swarm and emerge on the other side united with a male. The 

 insect-net was swept through the swarm a number of times. At each stroke the 

 mosquitoes would disperse somewhat but returned at once to their former posi- 

 tion and continued their dance, and there was no perceptible diminution of their 

 numbers. An examination of the captures showed 897 males and four females. 

 This count includes the female observed passing through the swarm, as narrated 

 above, and it is obvious that the other three females in the capture are not to be 

 considered as members of the swann. They may have entered the swarm un- 

 noticed in the manner described, or they may even have been hovering about out- 

 side of it. The observations of T. IT. Taylor (in Miall & Hammond, The Harle- 

 quin Fly) show a like condition in Chironomus. On a still evening his captures 

 from a swarm were 700 males, no females. On a windy evening, when the swarm 

 was thrown more or less into disorder by the breeze, a capture of 4300 specimens 

 included 22 females. 



" Upon turning to leave the mosquito-swarm another one was discovered close 

 by, hovering over and about a corn-stoock. The swarm extended about half way 

 down the side of the stook and kept on the south side of it, the mosquitoes all 

 facing northward. Although there was no perceptible breeze it was thought 

 that the attitude of the mosquitoes was in response to a current of air and sub- 

 sequent observations confirmed this supposition. It was but seldom that one of 

 the mosquitoes alighted on the corn, and as in the cloud first observed, all ap- 

 peared to be males. A round of the field showed that each corn-stook had its 

 swarm of mosquitoes, and furthermore, single stalks that remained standing 

 had small swarms dancing over them — sometimes of only six or eight individuals 

 — and the bushes and small trees on the edge of the field had their swarms. In 

 every case the mosquitoes faced northward and the swarm kept on the south 

 side of the object of attraction. Always the mosquitoes gathered over some 

 promiment object such as a tree or a projecting branch, a bush, a corn-stook or a 

 person. In this last case the swarm would move with the person and the only 

 way to get rid of it was by passing under some taller object where the swarm 

 would then remain. 



" On the following evening at five o'clock the field was again visited. Upon 

 approaching the region of the creek swanns of mosquitoes were noted over every 

 tall object — at the tops of telephone-poles, orchard-trees and shrubbery. On a 

 very tall elm, standing alone in a pasture, a swarm was dancing before a project- 

 ing branch. In the corn-field the swarms were found, as on the evening before, 

 over every prominent object and as the writer entered the field a swarm im- 

 mediately began to form over his head. This time, however, the position of the 

 swarms in relation to the objects was the opposite of the evening before— the 

 mosquitoes v/ere now all facing soutliAvard and they kept on the north side of the 

 objects. The trees on the south side of the field, some of them 25 or 30 feet high, 

 had immense clouds on their north sides. As on the evening before, there was 

 no perceptible breeze but the drift of smoke showed that there was a current of 

 air from the south. Station was taken near the row of trees bordering the field 

 and some swanns dancing before projecting limbs kept under observation. Re- 

 peatedly females were seen to issue from the foliage, dash into the swarm, and 

 emerge united with a male. When in copula the male and female face in oppo- 

 site directions, their bodies in a horizontal plane; the female dragging the male 

 after her.* The pair (or rather the female) would fly upward for a while and 



* " Goeldi (Os mosquitos no ParS, 1905, p. 74, pi. I, fig. 3a) describes and figures the copula- 

 tion of Stegomyia calopus. In that species the male clings to the under side of the female." 



