Fig. 7. Natural and peptide-induced ecdysis behavioural sequences of pharate pupae. (A) Natural behaviour was initiated by weak and occasional pre-ecdysis contractions (stippled line), which became gradually stronger. After apparent pre-ecdysis contractions for 1 h, animals initiated strong ecdysis peristaltic movements to shed the old cuticle in 10-12 min. Injection of pre-ecdysis-triggering hormone (PETH) induced pre-ecdysis behaviour for 30-60 min, which was then followed by ecdysis movements. Injection of intact animals or isolated abdomens with ecdysis-triggering hormone (ETH) induced the same pre-ecdysis contractions, but latency to the onset of ecdysis was generally shorter (25-44 min). As injected animals could not shed the old cuticle, strong ecdysis contractions lasted for up to 1 h (stippled lines). (B) Shaded areas and arrows indicate dorsoventral, leg and proleg contractions during pre-ecdysis induced by PETH or ETH injection. (C) Following pre-ecdysis, both peptides induced strong anteriorly directed ecdysis peristaltic movements (black arrowheads), which caused rupture of the old cuticle behind the head and moved it posteriorly with attached larval spiracles and trachei (white arrowheads).