Nilaparvata lugens and Sogatella furcifera are two primary planthoppers on rice throughout Asian countries and areas.Neonicotinoid insecticides,such as imidacloprid (IMI),have been extensively used to control rice planthoppers and IMI resistance consequently occurred with an important mechanism from the over-expression of P450 genes.The induction of P450 genes by IMI may increase the ability to metabolize this insecticide in planthoppers and increase the resistance risk.In this study,the induction of P450 genes was compared in S.furcifera treated with IMI and nitromethyleneimidazole (NMI),in two planthopper species by IMI lethal dose that kills 85％ of the population (LD85),and in N.lugens among three IMI doses (LD15,LD50 and LD85).When IMI and NMI at the LD85 dose were applied to S.furcifera,the expression changes in most P450 genes were similar,including the up-regulation of nine genes and down-regulation of three genes.In terms of the expression changes in 12 homologous P450 genes between N.lugens and S.furcifera treated with IMI at the LD85 dose,10 genes had very similar pattes,such as up-regulation in seven genes,down-regulation in one gene and no significant changes in two genes.When three different IMI doses were applied to N.lugens,the changes in P450 gene expression were much different,such as up-regulation in four genes at all doses and dose-dependent regulation of the other nine genes.For example,CYP6AY1 could be induced by all IMI doses,while CYP6ER1 was only up-regulated by the LD50 dose,although both genes were reported important in IMI resistance.In conclusion,P450 genes in two planthopper species showed similar regulation pattes in responding to IMI,and the two neonicotinoid insecticides had similar effects on P450 gene expression,although the regulation was often dose-dependent.