Characterization and comparison of general esterases from two field populations of the oriental migratory locust, Locusta migratoria manilensis （ Meyen ） （ Orthoptera： Acrididae） from Shanxi Province

General esterases in two field populations of the oriental migratory locust, Locusta migratoria rnanilensis (Meyen),respectively from Yongji and Linyi, Shanxi Province, were characterized and compared. No distinct difference was detected in banding patterns of general esterases between the two populations, when α-naphthyl acetate was used as substrate in nondenaturing polyacrylamide gel electrophoresis (PAGE) . Nevertheless, the general esterase activities in the Yongji population were 1.81- and 1.20-fold higher, respectively, than those of the Linyi population when α-naphthyl acetate and α-naphthyl butyrate were used as substrates. Increased esterase activity in the Yongji population might be correlated to several additional esterase bands detected with non-denaturing PAGE. Inhibition studies showed that 84.94% and 91.47% of esterases were Btype in Yongji and Linyi population, respectively. The Linyi population appeared to be more susceptible to malaoxon than the Yongji population. We estimated that such differences might be attributed to the different control practices for locusts in the two areas.