[Variation in organophosphate and carbamate insecticide resistance in relation to esterase activity in Culex (c.) quinquefasciatus Say, 1823 (Diptera: Culicidae)].

We determined the existence of the resistance mechanism by means of the esterase enzymes in a Culex (C) quinquefasciatus stock established in the laboratory. Bioassays were performed with insecticides such as malathion and temephos (organophosphoric) and propoxur (carbomate); two cycles were completed during one year. Resistance to malathion was higher. The presence of esterase enzymes in this stock was determined by using synergits and starch gel and paper filter electrophoresis techniques.