Orphan receptor possibly involved in the regulation of genes in the ecdysteroid cascade. Additional isoforms seem to exist. Isoforms differ in their N-termini. Both isoforms first expressed in stage-2 larvae and then highly expressed during larval and pupal molts. Only isoform E75A is expressed at the time of pupal ecdysis. Expression is induced by 20-OH-ecdysone which initiates and coordinates the molts. Lacks the first zinc-finger. Belongs to the nuclear hormone receptor family. NR1 subfamily.