Homozygotes die at various times from the very end of embryogenesis to the pupal stage. Most homozygous embryos hatch. Unhatched eggs contain fully formed larvae which are capable of head movement but do not hatch and eventually die. Hatched larvae show normal behaviour just after hatching, but movement slowly diminishes. Many animals that die during larval stages have double cuticles (judging from the number of mouth hooks). Larvae that survive to the third instar become incapable of movement by the end of this stage, cannot climb vial walls and die, but are capable of becoming pupae if transferred to wet paper. Z-disc-like structures are mostly normal in first instar homozygous larvae. However, striated muscle patterns of second instar larvae are heavily disrupted.