Mutant mushroom body neuroblast clones generated in newly hatched larvae and examined in the wandering third instar overextend processes from the calyx, with processes sometimes extending as far as the axon lobes. Overextended processes from the calyx are also seen in the adult. Mutant mushroom body neuroblast clones show a reduction in cell number compared to control clones, with the reduction being more pronounced in adult clones. These clones contain neither α or α' dorsal lobes.