A hole is seen in the blastoderm layer below the pole cells in embryos. The ventral furrow is extended posteriorly. Segments A8 to the telson are deleted. Segments A5 to A7 are expanded. Some twisting of the germband is seen. Labral and acron-derived structures are deleted. There is cell death in the head and tail region. Cephalic furrow and anterior midgut invagination are shifted anteriorly.
Eggs derived from homozygous females cellularise normally but become abnormal at gastrulation; the cephalic furrow is shifted forward, the posterior midgut is missing and the germband forms to the posterior end of the embryo. The embryos lack anterior head structures and structures posterior to segment A7 (the labral segment and telson).