Observations were carried out at a stream in the Western Transvaal, Republic of South Africa. 104 6 were given unique colour combinations which enabled recognition without recapture. The positions of males were recorded at each visit. Males established new territories each day but occasionally occupied the same territory for 2 or 3 days. Conspecific males were excluded from the territories but tandem pairs were allowed to oviposit. Detailed analyses of territorial behaviour were carried out by noting the type, duration, outcome and temporal distribution of 165 flights by 2 adult d. Males spent between 12.1% and 14.3% of their territorial occupation in flight (mean 13.3%). Flight activities consisted of patrolling (44.8% of all flights, 58.2% of total flight time and 23.3 flights/h), shifting flights (24.9%, 8.6% and 14.3 flights/h), and investigatory flights towards movements (30.3%, 33.3% and 15.4 flights/h). The mean durations of patrolling, shifting and investigatory flights were 12.2, 2.9 and 18.2 s respectively. The (light season was from mid-September 1989 to mid-June 1990.