Fig. 8. Effects of 20-hydroxyecdysone (20E) or the ecdysteroid agonist tebufenozide (RH-5992) on sensitivity to ecdysis-triggering hormone (ETH) in freshly ecdysed fifth-instar larvae or isolated abdomens. (A) Injection of 20E (arrowhead) induced sensitivity of isolated abdomens to ETH within 1–2 days. The initial ETH treatment (arrow) triggered pre-ecdysis (PE) behaviour, but subsequent peptide injections 1 and 2 days later failed to induce this behaviour (No PE). (B) Repeated injections of 20E into isolated abdomens followed by ETH treatment 2 days later always resulted in pre-ecdysis contractions (PE). (C) Injection of tebufenozide (5 µg) into intact ecdysed larvae induced the production of new cuticle and sensitivity to ETH within 1–2 days. These larvae responded to ETH injection with pre-ecdysis and ecdysis behaviour (PE+E). See text for details. Numbers refer to days after ecdysis into the fifth-instar larva.