Receptor for ecdysone. Binds to ecdysone response elements (ECRES). May play a role in the implementation of the choriogenic program at the end of vitellogenesis. Heterodimer of ECR and CF1. It is present in constant amounts in follicular cells throughout vitellogenesis but disappears transiently at the onset of choriogenesis and reappears during the later stages of choriogenesis. Belongs to the nuclear hormone receptor family. NR1 subfamily. It is uncertain whether Met-1 or Met-61 is the initiator.