Abstract
Relations between esterase activities in the third-instar larvae from various silkworm strains (94 strains) and their Sumithion-susceptibilities were described in this paper. Interstrain difference in activity of esterase hydrolysing β-naphthylacetate was correlated with Sumithion-susceptibility of each strain, i.e., the silkworm strain showing higher activity of esterase was generally less susceptible to Sumithion. Agar-gel electrophoretic study revealed that the esterase of the third-instar larva was separated into six bands which hydrolyze β-naphthylacetate. Of these six bands, the E_3-esterase with medium mobility was most commonly detected in the larvae from higher susceptible larvae. When Sumithion was topically applied to the larvae, the esterase was found on electrophoretic pattern as a temporary change of mobility and disappearance of some specific esterase-bands.
