Homozygous clones in the outer proliferation center (OPC) neuroepithelium are small and composed of only a few cells. The cells retain columnar neuroepithelium cell morphology. Some of the mutant cells are extruded from the neuroepithelium and basally enter the medulla cortex. These extruded cells change morphology and become rounded or irregular in shape.
Lethality occurs during the first and second larval instars.
P{lacW} not verified as causing the lethality.