The adult rice water weevil (Lissorhoptrus oryzophilus) is small (about 1/8 inch or 3mm long). It resembles the cotton boll weevil and other snout beetles. The adult rice water weevil feeds between the veins of rice leaves, leaving behind whitish scars. Even when the adult cannot be found, these scars indicate their presence. Rarely does this type of damage cause economic damage.

Shortly after emerging from overwintering sites, the adults mate. They overwinter in wooded areas or debris near rice fields. In Louisiana, as many as three generations may be produced. Female adult rice water weevils lay eggs at or below the water line. The adults can often be found swimming or well below the water line, especially if it is excessively hot or cold. Free water is necessary for egg laying and hatching.