Neochetina eichhorniae Warner has four generations per year in southern Louisiana. The adult sex ratio (males to females) in the field was 1:1, and adults, larvae, and pupae overwintered. Population intensities as high as 8 weevils per plant were observed in August 1980. Adult weevil longevity averaged 57.8 ± 9.6 days under laboratory conditions. Oviposition occurred mainly at night, and an average of 2.8 ± 0.4 eggs were deposited per 24 h. Most eggs were deposited on the lower leaf surfaces. Larvae eclosed in ca. 8 days and completed larval development in ca. 41 days when reared under laboratory conditions. Pupation was not observed in the laboratory but occurred on the upper root system of the plant just below the water surface in the field. The number of feeding scars per day was not significantly different between sexes. Mating frequency was 50% greater at night than during the day. Adult feeding preference was upper leaf surface, lower leaf surface, and leaf petiole, respectively. Patasson sp. (Hymenoptera: Mymaridae) were reared from weevil eggs on one occasion.