Insect ecdysone receptors are currently better characterized than those from other arthropods, and mimics of ecdysteroids are used commercially as caterpillar-selective insecticides.

[3] This in turn leads to the activation of many other genes, as evidenced by puffing of polytene chromosomes at over a hundred sites.

Ultimately the activation cascade causes physiological changes that result in ecdysis (moulting).

Based on sequence homology considerations,[6] some researchers reserve the term USP for the EcR partner from lepidopteran and dipteran insects, and use RXR in all other instances.

Its natural ligand remains uncertain, and USPs appear to be locked permanently in an inactive conformation.