Territorial behaviour in Platycnemis echigoana Asahina at sunflecks in climax deciduous forests (Zygoptera: Platycnemididae)

Diurnal change in territorial behaviour at a sunlit point in a stand (sunfleck) was studied by observation in climax forests of Urabandai, Fukushima Pref., Japan. The number of patrolling flights of a male occupying a sunfleck increased towards noon and decreased afterwards. The flight height above the perching site was around 50 cm, including a round-trip flight along the periphery of the sunfleck. Hovering above the perching point was also observed. During a patrolling flight males did not encounter conspecific males, females or other insects, so that such a flight may be understood as a display of the occupation of the sunfleck. Encounters with conspecific males mainly occurred when the male was perched at the sunfleck. The number of fight encounters was high until noon, while non-aggressive encounters increased in the evening. High success rate in capturing prey occurred in the evening. Males moved out from among sunflecks in the morning, but stayed at one sunfleck in the evening. The habitat of P. echigoana in relation to its territorial behaviour is also discussed.