Penetration and fate of methomyl and its oxime metabolite in insects and twospotted spider mites.

The penetration and fate of methomyl and its oxime metabolite, methomyl oxime or S-methyl N-hydroxythioacetimidate, were examined in house flies (Musca domestica Linnaeus), face flies (Musca autumnalis De Geer), black cutworm larvae (Agrotis ipsilon (Hufnagel), and twospotted spider mites (Tetranychus urticae Koch). Generally, penetration and metabolism of methomyl-1-14C were rapid in insects and spider mites although differences in rates among the different test organisms were observed. Metabolites from methomyl included CO2, methomyl oxime, and several unknowns. Penetration and metabolism of methomyl oxime-1-14C also were rapid in insects. Metabolites from methomyl oxime included a small amount of CO2 and several unidentified compounds. Organosoluble metabolites from methomyl oxime generally displayed similar chromatographic behavior as those from methomyl. Methomyl was hydrolyzed to its oxime metabolite, which, apparently, was further metabolized to 14CO2 presumably via a Beckmann rearrangement reaction.