ecdysone receptor holocomplex A heterodimeric complex containing the products of the insect genes Ecdysone receptor (EcR) and ultraspiracle (usp). Binding of ecdysone promotes association between the two subunits, and the receptor complex then initiates molting and metamorphosis by binding DNA and regulating the transcription of target genes. GO:0008230 cellular_component RNA polymerase II transcription regulator complex