Receptor for ecdysone. Binds to ecdysone response elements (ECRES). Heterodimer of USP and ECR. Only the heterodimer is capable of high-affinity binding to ecdysone. A peak level expression is seen in the fat body of previtellogenic female mosquitos at one and two days after eclosion, levels fall three-fold at three days posteclosion. Transcripts exhibit dramatically different patterns of expression after blood meal-triggered activation of vitellogenesis in the fat body. Isoform B is highly expressed and reaches its peak at 4 hours pbm (post blood meal). Isoform A peaks at 16-20 hours, when isoform B expression is lowest. Belongs to the nuclear hormone receptor family. NR1 subfamily.