The circadian flight activity of mosquitoes breeding in septic tanks in Jos, central Nigeria, was studied using exit and entry traps. The pattern of peak activity in Culex quinquefasciatus, Culex horridus and Culex cinereus leaving septic tanks was the same between males and females. Aedes aegypti left the tanks earlier than any of the Culex species. There was a difference in time and pattern of peak activity between sexes in this species. Also, a significant difference in peak activity between females of different physiological states was noted in Cx. quinquefasciatus.
