Mitotic clones on the ventral wing surface cause wing bubbles. Embryos exhibit normal epidermis and resultant secreted cuticle, defects lie in internal tissues. Somatic muscle detach and round up. Gut morphogenesis is defective: anterior midgut does not become a slender tube and only two fat gastric caecae are formed. The ventral nerve cord does not fully condense.
Class 0 mutation.