Laboratory Studies on the Reactions of Simulium Larvae to Insecticides

III. The Reactions of Simulium damnosum Larvae to Dieldrin

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  • Liberian Institute of the American Foundation for Tropical Medicine, Inc., Harbel, Liberia


Under laboratory conditions a 1-hour exposure to Dieldrin produces a 24-hour mortality of 100 per cent in full grown Simulium damnosum larvae at various concentrations down to 0.001 parts per million. Dieldrin (HEOD) in acetone was effective less than a 20 per cent emulsifiable concentrate tested. Although 0.001 ppm produces such a high mortality, the efficiency of the insecticide falls off rapidly below that point, and there is no appreciable effect after a 1-hour exposure to 0.0002 parts per million. In comparing the best results obtained with Dieldrin—in emulsion form—with the best results obtained with DDT—in acetone—Dieldrin appears to be effective at concentration at least 10 times lower than with DDT.