The Behaviour and Mortality of Anopheles maculatus and Culex fatigans in experimental Huts treated with DDT and BHC

Abstract

In untreated huts, A. maculatus fed at all hours of the night and the majority left the huts before 8 a.m. Large numbers of culicines (mostly Culex fatigans) were recovered; about 80% were blood fed. Residual deposits of DDT at 200 mg. and BHC at 40 mg. gamma isomer per sq. ft. were both effective for 12-16 weeks against A. maculatus. With DDT, 63% initial, and 83% 24-hour mortalities were recorded over 16 weeks. With BHC the initial mortality dropped from 100% in weeks 1-4 to 19% in weeks 12-16; the 24-hour mortality, almost 100% for weeks 1-10, was still 88% for weeks 12-16. DDT apparently had little effect on the feeding of A. maculatus; with BHC there was a reduction in the percentage fed. DDT was relatively non-lethal to C. fatigans, but had a marked irritant effect on them. BHC killed all C. fatigans which entered for 2 weeks. BHC was repellent to mosquitoes. Mansonia uniformis was susceptible to DDT and BHC residues.