Development arrests at very early stages in most embryos preventing cuticle formation. The remaining eggs support cuticle formation but have a reduction or complete absence of segmentation. Posterior spiracles are always present. Limited zygotic rescue, 10% survive to adulthood. Double mutants with tor unalters the percentage of late lethal embryos, double mutants with trk reduces late lethality to 10% and double mutants with fs(1)M31901 yield embryos that develop cuticle.
Wild type fertile revertants can be generated by P-element excision.