During territorial behaviour, aggressive attacks among heterospecific odon. 3 3 are common and may cause a separation of niches, based on the preferred sites for territorial defence. Here, territorial behaviour and the characteristics of territories in <Jdof Erythrodiplax media, Micrathyria catenata and M. hesperis are described and their territorial fidelity, capturing and marking of <3 3 are discussed. In all spp. studied, there was a clear distinction among the microhabitats defended as territories. In both Micrathyria spp., 3 3 seem to defend territories with defined resources. In E. media, the defended resources are less evident. Its 3 3 are highly aggressive and show high territorial fidelity but, apparently, they lose the territory if they stay away from water for at least one day.