The reproductive activity of two Pseudagrion species in the same habitat (Odonata : Coenagrionidae)

The reproductive activity of two closely related species, Pseudagrion massa icum Sjostedt and P. salisburyense Ris was examined relative to environment al factors. The abundance of both species was positively correlated, sugges ting a weak influence of interspecific competition. The most important abio tic factor influencing the activity of the two species was cloud cover. Mal es of the two species showed a strong spatial separation in perching positi on relative to vegetation type, perch height and distance to the banks. The proportion of males actively engaged in reproduction rose significantly wi th time of day but was independent of total male density and the relative i mportance of either patrolling or perching behaviour. Males of both species were found to be non-territorial, which is exceptional for the genus Pseud agrion. This is discussed relative to high territory retention costs at hig h dragonfly densities.