Emergence patterns of Culex mosquitoes at an experimental constructed treatment wetland in southern California

The emergence patterns of mosquitoes inhabiting a 0.1-ha experimental wetla nd in southern California were monitored using emergence traps during the l ate summer and autumn of 1996. Culex erythrothorax was the largest contribu tor to emerging populations, comprising 94% of the total emerged adults wit h an average emergence rate of 59 adults/day/m(2). None of the Culex specie s exhibited a pattern of emergence associated with water depth (range: 5-60 cm). Culex quinquefasciatus and Cx. tarsalis did not show a pattern of eme rgence associated with the inflow-outflow gradient; however, Cx. erythrotho rax emerged in higher numbers along a transect at the middle of the wetland than from near the inflow and outflow. Additionally, the number of emerged Cx. erythrothorax was positively correlated with the density of vegetation below emergence traps. The comparatively large number of adults emerging f rom the middle of the wetland was most likely caused by a trade-off between an increasing gradient of resource abundance and a decreasing gradient of toxic compounds from the inflow to the outflow of the small wetland.