Observations on the swarming of mosquitoes were conducted in the flood plain forest of South Yamal (67 degrees N.L.). The individuals of A. communis made 83 to 94% of the swarming males. Their number in swarms varied from 30 to 800 specimens. The dynamics of the swarming males number depends on the rate of their emergence from the pupae. At the mass emergence the number of swarming males was 3 times higher though the increase in the general size of the population was negligible. Synchronization of the swarming time of males was also favoured by warm windless weather.