ETH^25b homozygotes or ETH^25b/Df(2R)196 animals exhibit an ecdysis deficiency phenotype. Almost all die with a double vertical plate suggesting death at ecdysis. These animals show a shrunken body appearance, thick trachea and partial ecdysis of old cuticle both exteriorly and within the tracheal system. This is called a 'buttoned-up' phenotype, describing an inability to extricate old mouthhooks and vertical plates from the new sclerotized structures. Tracheal collapse and inflation of new trachea are also delayed for ~1.5 hours in mutant and pre-ecdysis behaviours are completely absent. In the absence of these events 'ecdysis-like' behaviour occurs early, around the dVP stage with a large variation among individuals. This differs from wild-type ecdysis behaviour in several respects. First, normal forward thrust movements to plant the old mouthparts in the substrate are absent. Instead, animals engage in swinging head movements, and repeated extensions and retractions of the mouth. Second strong backward thrust movements, which normally result in separation of the spiracles and ecdysis of tracheae, are also absent. Although some backward movements are observed, animals are unsuccessful in detaching the old spiracles and tracheal linings. Some turning behaviour resembling forward escape is observed. These ecdysis like behaviours are repeated on an irregular basis for 1 to 3 hours. Some time after the occurrence of delayed tracheal collapse and inflation, ecdysis lie behaviours become more like normal ecdysis. The majority (78%) are able to move through an anterior dorsal opening on the old cuticle that appears after repeated ecdysis movements (unlike in wild-type where the opening is created by the removal of the old mouthparts). A small fraction (~2%) of larvae undergo successful ecdysis and development through the second instar but all succumb following ecdysis failure at the 2nd to 3rd instar transition. ETH^25b individuals rescued by the injection of ETH^1.cPa at the dVP stage, have a normal ecdysis behavioral sequence, but 25% of ETH^25b flies fail to successfully shed the old cuticle.