Territorial behaviour of the African libellulid Orthetrum julia Kirby (Anisoptera)
Odonatologica , Volume 9 - Issue 1 p. 75- 99
The observations were carried out on a colony of the pale montane form of O.j. falsum Longf. (8 April – 4 June, 1977) at Naisi, Zomba Mountain, southern Malawi. 277 dd and 13 99 were given unique numbers on the wings which enabled recognition without subsequent recapture, and the positions of territorial dd were recorded accurately each time the colony was visited. The most frequently seen individuals showed the greatest consistency of localization. This indicates that the most frequently seen individuals were superior in territorial defence and hence tended to return most often to a chosen area. Whereas a territory might measure up to 10 m in diameter, the central zone, where the insect spent 75% of its territorial time, would be only about 2.5 m2, or less. Many territories were much smaller than 5 m in diameter. The outer zone territories of neighbouring insects often overlapped. In the late afternoon, the highly structured territorial system broke down and many widely ranging dd were observed to invade the colony area. In the mornings the territories tended to be occupied as soon as they were in partial or full sunlight. The territorial dd spent 5-13% of their time in flight, depending on weather conditions. About 60% of all territorial flights were aggressive and 20% were feeding flights. 99 occurred at the breeding sites at any time during the territorial period, but observed matings took place 10.13-14.45 hrs. The mean copula duration was 29.5 sec. Usually the 9 oviposited in the d’s territory immediately after copulation there and was attended by him, hovering over her. The mean survival for mature dd was 9.0 days and maximum observed survival was 51 days.
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