The steroid hormone,20-hydroxyecdysone,hereafter referred to as eedysone,controls the expression of vast networks of genes during insect development and reproduction.We have cloned and characterised full-length cDNAs encoding both EcR and USP subunits for ecdysone receptors from insect pests spanning three orders:the cotton bollworm Helicoverpaarmigera (Lepidoptera),the Australian sheep blowfly Lucilia cuprina (Diptera) and three members of the Hemiptera,the peach aphid Myzns persicae,the silverleaf whitefly Bemesia tabaci and the green vegetable bug Nezara viridula.The cDNAs have been placed into expression vectors and transfected in to CHO and CV 1 mammalian cells along with reporter genes functionally linked to ecdysteroid responsive promoters.The ability of the receptors to activate reporter genes in response to insect ecdysteroids and phytoecdysteroids has been studied.The responses of our cloned ecdysone receptors to different ligands will be discussed.