Citrus groves in Indian River County in Florida, irrigated by crown-flooding, have provided an extensive new habitat for the mosquitoAedes vexans(Meigen).Eggs are laid mainly under tree canopies at the crowns of citrus grove furrows and require inundation as a hatching stimulus. Normal rainfall provides insufficient water depth in the furrows to hatch many eggs, but crown-flood irrigation hatches large numbers. Therefore, irrigation during periods of drought stimulates mosquito production.