Mutation causes abnormal trichome differentiation. Mutants exhibit visible disc abnormalities: discs are small. Clones induced in wild type discs are abnormal: clones are generated at a lower frequency than expected, they are small and have a significantly elongated shape along the proximodistal axis. Clones in the wing run preferentially along the veins or close to them and have non-autonomous effects on the proliferation of neighbouring territories, leading eventually to a reduction in wing size.