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Ecdysteroids play an important role in regulating diverse physiological processes in arthropods,such as molting,metamorphosis,reproduction and diapause.Ecdysteroids mediate the response by binding to a heterodimeric complex of two nuclear receptors: the ecdysone receptor and the ultraspiracle (USP).To investigate the role of USP in development of the Asian gypsy moth (Lymantria dispar),a USP cDNA was obtained from the transcriptome of L.dispar and verified by PCR.In-depth profiling of transcript levels of L.dispar USP-1 (LdUSP-1) at different developmental stages and over time in third-instar larvae and different tissues isolated during the third-instar stage of L.dispar was then carried out.Transcript levels of LdUSP-1 were relatively high before 72 h in the third-instar larvae after ecdysis and in the adult male.The function of LdUSP-1 in molting was analyzed by knock-down of LdUSP-1 in third instar larvae using RNA interference.Silencing of LdUSP-1 significantly downregulated the transcript level of E75,an ecdysone-inducible gene,and of Sad,a Halloween gene.In addition,the duration of the third-instar stage was slightly shortened and larval mortality increased after the LdUSP-1 knockdown.