Abstract
Susceptibility of Culex quinquefasciatus larvae from seven islands (Okinawajima, Agunijima, Miyakojima, Ishigakijima, Iriomotejima, Yonagunijima and Minamidaitojima), Okinawa Prefecture, to eleven insecticides was tested in 1989. The LC_<50> values of malathion (and resistance ratio as compared with a susceptible strain of Ogasawara Is.) in these strains were high, ranging from 0.111ppm (resistance ratio : 7.4) in the Ishigakijima strain to 1.838ppm (122.5) in the Miyakojima strain. These strains were, however, susceptible to the other ten insecticides, viz. p, p'-DDT, seven organophosphates, propoxur (a carbamate) and permethrin (a pyrethroid).
