The spatial distribution and preadult mortality patterns of 4 cohabiting species of Aedes mosquitoes were studied in a temporary vernal pool at Mt. Carmel, CT, from March to May 1990. The dominant species was Ae. stimulans (79.9%), followed by Ae. canadensis (10.7%), Ae. excrucians (7.5%) and Ae. cinereus (1.9%). First instar larvae of all species aggregated at the edge of the pool and then dispersed to deeper regions as they matured. Larval mortality was high, and the majority occurred during the first stadium (80.9% for Ae. canadensis, 88.9% for Ae. excrucians, 89.1% for Ae. stimulans and 90.0% for Ae. cinereus). A predatory chaobrid, Mochlonyx cinctipes, was implicated as the major mortality factor affecting larval populations.