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mosquitoes is especially dependent upon meteorological conditions. It is most con- 

 spicuous towards evening, more especially after calm fine days; on windy days it 

 may take place, but then only in sheltered places behind large trees, buildings etc. 

 In the swarms the mosquitoes are almost always directed facing the wind. Of great 

 interest is the old narrative of Wahlberg (1847 p. 257), relating to the mating 

 habits of the mosquitoes of the far North. Undoubtedly it deals with one of the 

 Aedini, most probably with A. nigrijies. He says that travellers, as known well, are 

 attacked by immense numbers of female mosquitoes, but that for a long time it 

 was quite an enigma to him where the males were to be found. A clergyman then 

 told him, that the females were often found upon the surface of the lakes, beaten 

 down by rain and wind in such endless numbers that when blown ashore, they 

 formed thick wind rows. Wahlberg then observed, that no males were to be found 

 near the ground, just where the females in immense numbers tormented him and 

 his fellow-travellers. But from high up in the air he heard a loud singing noise 

 which was found to be produced by immense swarms of mosquitoes dancing in 

 separate flocks. These swarms being examined they were found to consist almost 

 exclusively of males. This indicates that the males of the Culex, like those of Chi- 

 ronomids and some other non-biting gnats, keep to themselves in a higher stratum 

 of the air, where they flock together in dancing swarms, more especially towards 

 evening, and tempt the females to come up by the noise of their wingbeats. 



During recent years I have often had an opportunity to observe the mating 

 habits of our mosquitoes; more especially those of C. pipiens, 0. cantans, 0. com- 

 munis, Anopheles maculii>ennis and A. bifurcatus. I shall here only dwell upon the Culicines. 



In the latter part of September small clouds of males of C. pipiens may be 

 observed on fine autumn evenings everywhere round Hillerod. On five successive 

 evenings I have observed the swarms in my garden. The swarms always consisted 

 of males only; they always stood in sheltered places, commonly behind a large 

 lime tree; the mosquitoes always faced the wind which was very slight. The swarm 

 was formed about six o'clock, and was still hovering after it was so dark that I 

 could see nothing. The single individuals were flying up and down, commonly at 

 the same rather slow speed, but suddenly it could be observed how the whole 

 swarm got into the greatest excitement, all the males now flying at a much higher 

 speed. The swarm almost invariably stood in the same place, but I got the im- 

 pression that now and then some of the males left the swarm and settled on the 

 leaves of the lime; at all events many males were sitting here. The shape of the 

 swarm was that of a column, commonly about two or three meters high and one 

 meter thick. The height from the ground was about Wxe or six meters. I observed 

 the mosquitoes by means of a Zeiss (power x S). I estimate the number of animals 

 from some hundreds at about six o'clock, to some thousands when the swarm was 

 largest, at sunset between seven and eight. In the course of these two hours I saw. 

 most probably about fifty times, larger and darker mosquitoes direct their way from 

 the outside into the swarm. I could observe the females about two or three meters 



I). K. D. Vidcnsk. Selsk. Skr.. nalurvidensk. og matbem. Aft!. S. Raekke, VII, 1. 20 



