Territorial and courtship displays and their relation to male ornamentation were examined in 11 spp. in N Borneo. Males of all spp. were territorial, guarding a small area of oviposition substrate and attempting to mate with ovipositing females. Most spp. exhibited a ritualized threat display, in which males faced each other and displayed the terminal markings on their wings. In the genus Libellago there was a pronounced stationary wing display, in which the outstretched forewings were held completely still for about a second. This behaviour did not occur in L. hyalina which lacks markings on its wings. Apart from L hyalina, some form of courtship occurred in all spp. for which information was available, typically involving the male swinging to and fro in a semicircle to the side of the female, while displaying and vibrating his pruinescent legs. Variations included display of various markings on wings and abdomen, probably associated with species recognition, and in Rhinocypha aurofulgens, standing on the substrate during courtship, a modification probably associated with loss of pruinescence on the legs in this spp. Interspecific interactions were frequently intense, and probably have been important in the evolution of displays. An outline of possible evolutionary relationships among display elements is suggested.