Density-dependent behaviour in Aeshna cyanea (Müller) males at the mating place (Anisoptera: Aeshnidae)

Marking experiments showed that under high male density conditions the behaviour of A. cyanea males is strongly territorial; when male density is low, long-range patrol flights without territorial attachment are observed. It is suggested that this variable behaviour is an adaptation to fluctuations in male density which maximizes mating chance.