Studies on organophosphate-resistance and esterase activity in the mosquitoes of the Culex pipiens group. I.

Study on the relations between diazinon-resistance and esterase activity in Culex pipiens pallens larvae was carried out by the thin layer electrophoresis developed by Ogita. Esterase activity of the 4th instar larvae revealed by β-naphthylacetate hydrolysis was separated into 4 bands. Diazinon-resistant colonies showed marked higher E_2 and E_3 esterase activities than susceptible strain. The E_2 or E_3 esterase has an ability to hydrolyse phenylacetate and methyl-n-butyrate, but not acetylcholine.