Some aspects of territoriality in Orthetrum coerulescens (Fabricius) (Anisoptera: Libellulidae)

A colony of O. coerulescens was observed in southern England during July, 1980. Detailed analyses of territoriality were carried out by noting the type, duration and temporal distribution of 1323 territorial flights of 7 adult males. Territorial attachment varied according to age and from individual to individual. Up to 14 territories (7-16 m in length; mean 10.5 m were established along 154 m of small stream. Territorial males spent between 4 and 19% of their time in flight (mean 13%). Territorial flight activities were complex and often incorporated a number of different components. The dominant flight activities involved feeding (53% of flights and 12% of flight time), patrolling (40% and 61%) and aggression (17% and 18%). Aggression and patrolling were frequently associated as combined activities. Feeding, if combined, was mostly linked with patrolling. About 75% of feeding. 33% of patrolling and 25% of aggressive flights were unassociated with any other components. The mean durations of uncombined feeding, aggressive and patrolling flights were 2.7. 12.0 and 17.8 sec respectively. Other night components (minor changes of position; stabilizing; disturbance; various types associated with reproductive behaviour) collectively comprised only 7% of the total night time. Territoriality often commenced at about 10.30 BST, but was weather determined. Patrolling and aggressive (lights were at a maximum around 12.30 hr, whereas feeding was maximised early in the morning territorial period and from 16.00-17.00 hr. Copulatory activity was observed on nine occasions (12.42-17.50 hr), when copulations ranged from 5 sec to nearly 25 min, with a mean of 7 min 11.5 sec. Mature non-territorial males ("wanderers") were seen frequently on occupied territories.