Embryonic and larval development is normal in mutant animals. Gas bubble formation is on schedule. However the displacement of the bubble appears abnormal and animals fail to complete head eversion. Random bubble displacement continues for several hours and internal pulsions can be detected for several days. A few animals develop further and show a striking cryptocephalic phenotype in which eye pigmentation is evident within the thorax. The larval mouthparts remain attached to the imaginal head structures. In these animals, although the abdominal cuticle is formed at pupation, segment differentiation, as seen by bristle formation, does not extend beyond the proximal abdominal segments.