Abstract
Mass flight activity of Phyllonorycter ringoniella was observed early in the morning soon after sunrise from 16 to 20 September 1999. The number of moths in a swarm varied from about 30 to 50. Swarms were composed of only males, possibly because the observations were conducted late in the season when all the females had finished ovipositing, and their numbers had decreased. The male moths were flying in a repeated, wave-like movement close to the canopies of some apple trees. The observations indicated that the mass flight activity was not dependent on the presence of female moths, but was controlled by male-specific circadian rhythms.
