A series of novel N-tert-butyl-N'-thio[1-(6-chloro-3-pyridylmethyl)-2-nitroiminoimidazolidine]-N,N'-diacylhydrazines were synthesized by the reaction of chlorosulfenyl(N-tert-butyl-N,N'-diacylhydrazines) with 1-(6-chloro-3-pyridylmethyl)-2-nitroiminoimidazolidine (imidacloprid) in the presence of sodium hydride. Their larvicidal activities were evaluated. All of them exhibited insecticidal activities against Oriental armyworm and bean aphids. Toxicity assays indicated that at higher concentrations (200 mg L(-1)) the title compounds can kill aphids as fast as the parent imidacloprid in 2 h, whereas at lower concentration (10 mg L(-1)), the title compounds can induce a premature, abnormal and lethal larval moult after 3 days of treatment, like the parent diacylhydrazines.