The multicopper oxidase (MCO) family of enzymes includes laccases, ascorbate oxidases,bilirubin oxidases and a subgroup of metal oxidases.On the basis of a bioinformatics investigation, we identified 7 genes encoding putative multicopper oxidase proteins in the genome of the brown planthopper (BPH), Nilaparvata lugens (Hemiptera: Delphacidae).MCO1 and MCO2 are conserved,while others diverse in insects.Analysis of developmental and tissue-specific expression patterns revealed the following: NIMCO2 was mainly expressed in the integument, and its expression peaked periodically during molting;NIMCO3 was an ovary-specific MCO gene with a high expression level only at the adult stage;N1MCO4 was a salivary gland-specific MCO gene that was expressed at all developmental stages;N1MCO5 only had short-term expression in the middle of the fourth instar stage and was expressed mainly in the gut;N1MCO6 had a developmental expression pattern similar to that of N1MCO2 and was expressed in most N.lugens tissues;and NIMCO1 was expressed in most N.lugens tissues except for the testis, whereas N1MCO7 was mainly expressed in the gut and the Malpighian tube.BPHs injected with double-stranded RNA (dsRNA) targeting N1MCO2 failed to pigment and sclerotize,were colorless and soft-bodied and subsequently died in a short time.Lethal phenotypes were also observed in insects challenged by dsRNA targeting NIMCO6.However, no observable morphological or internal structural abnormality was obtained in the insects treated with dsRNA for N1MCO1, N1MCO3,N1MCO4, NIMCO5 or N1MCO7.