RESUMO
The genetics and mechanism of malathion resistance in the adults of An. stephensi [BAN-S], Was studied. Nine successive generations of malathion selection in the adults resulted in an increase in LTSO of about 3-fold. The crossing experiments indicated that the resistance is inherited as partially dominant character with no indication of sex linkage. The results of back-crosses suggested that probably more than one genetic factor are responsible for malathion resistance. Synergist study with TPP and PB indicated that the involvement of carboxyesterase as the main resistance factor in An. Srephensi. The cross- resistance spectrum of malathion resistance with pirimiphos- methyl, DDT and dieldrin were studied in the selected strain. The results did not show any relationship between resistances to malathion, DDTand pirimiphos- methyl. Dieldurin test on the selected and uselected strains showed that malathin resistance could increase dieldrin resitance