Toxicity of Rose Bengal to Various Instars ofCulex pipiens quinquefasciatusandAedes triseriatus

Abstract

Treatment of water containing mosquito larvae with rose bengal and subsequent exposure to visible light causes mortality within hours. The light-initiated mortality is a function of dye concentration and exposure time. The larvae of the Culex species are more susceptible to rose bengal than the larvae of the Aedes species, i.e., 4th-instar Aedes LT 50 values were from 5–10 times higher than those for Culex over all concentrations. Earlier instar larvae exhibited a higher degree of response to rose bengal than the later instars. First-instar larvae are up to 20 times more quickly killed than 4th-instar larvae. Physiological and morphological abnormalities occurred resulting from larval treatment with rose bengal which appeared to involve the improper formation of chitin in the pupal stage.