Nocturnal riceland mosquito populations in southern Louisiana were monitored using nonbaited CDC miniature light traps. A mixed population of Anopheles quadrimaculatus, An. crucians, Psorophora columbiae and Culex salinarius adults was collected in a livestock occupied barn. Highly variable numbers of all 4 species were trapped in areas away from the barns. Species density at any given trap location was not related to trap location, type of habitat surrounding the trap or brush density near the trap. Captures of anophelines were not affected by moonlight, whereas trap collections of culicines were lower on moonlit nights. Mean numbers of anophelines captured at night in traps exhibited a linear function of trap distance from the barn, with higher catches at locations farther from the barn. No such function was observed for culicines.