Abstract
Mass flight activity of the apple leafminer Phyllonorycter ringoniella was observed in the field to explore whether it was associated with mating. Flight activity started around the time of sunrise. About 15 min later, small swarms joined to become a larger, and denser swarm. This lasted about half an hour before the insects dispersed. Although female moths were present in the tree crown throughout the day, they did not participate in the swarms, which were composed of only males. The swarms actively responded to the females that were present among the branches as well as those that were experimentally offered to them to test their response. Mating usually occurred on leaves. Mating began only while the male moths were massively and densely swarming, and lasted about 1 h at the most.
