Adult male Odon. spp. and related environmental variables were recorded around a farm dam in South Africa. Although the species-environment correlation was low at the microhabitat level, it was stronger at the larger spatial scale of biotope. Microhabitats were classified on the basis of species that preferred sunlit or shaded conditions. This confirms results from earlier studies on adult dragonfly assemblages at both still and running waters. Thermoregulatory requirements of species were important in determining the presence of adults in microhabitats. Microhabitat overlap between congenerics was low, suggesting the influence of past competition. Some spp. had much narrower Eltonian niches than others, and similarly there were various degrees of tolerance to changes in conditions. The stenotopic spp., being sensitive to certain conditions were therefore better indicators of changing microhabitat or biotope conditions. The implications of these findings for conservation are discussed, and it is suggested that a wide range of plant physiognomy and hence also wide differences in thermal conditions are created to cater for a variety of rare, stenotopic spp., as well as abundant, eurytopic ones.