Swarming is a requisite for mating in populations of Aedes communis and Ae. stimulans in Maine. Swarming can be induced in a large, walk-in cage in the laboratory by proper control of humidity, temperature and light. The act of mating appears to be controlled by the behavior of the females and is usually completed during flight. Receptive females may vary in age from 5 to 12 days. The physiological conditions that give rise to receptive females are unknown. Field studies suggest that numerous univoltine Aedes species swarm and mate under similar conditions.