Dusk mating flight in the swift moth, Endoclita excrescens(Butler)(Lepidoptera: Hepialidae).

Abstract

Laboratory-reared and wild adults of Endoclita excrescens (Butler) showed a mating flight at dusk. They began to fly soon after sunset and stopped flying at the beginning of darkness both in the cage and in the field (a forest in Chiyoda Town, Ibaraki Prefecture, Japan) during the period from 1 June to 20 October 1998. It is suggested that their flight activity is closely related to light intensity. Usually, the males began their flying about 4 min prior to the female flight. Mean flight period of the males per night was about 15 min in the cage and about 7 min in the field. For the females, it was about 10 min in the cage and 2 min in the field. The flight behavior of males was strikingly different from that of the females. The males flew swiftly and often showed a swinglike pendulum flight but the females did not. The males flew around a branch of a particular tree in a particular spot and sometimes formed a small group consisting of 2 to 4 individuals. Although no actual copulation was recorded, all other phases in the mating behavior were observed.