Homozygous larvae never form puparia. Mutant larvae have smaller imaginal discs than normal (the maximum size is smaller than the size of wild-type late second instar discs) which cannot differentiate into adult structures when injected into metamorphosing normal larvae. The eye-antenna, leg, wing, haltere and genital discs are abnormal. Late second instar mutant wing discs and eye-antenna-brain complexes injected into wild-type adult females grow slightly in in vivo culture, but do not reach the size of wild-type early third instar discs, and are unable to differentiate into adult structures when injected into metamorphosing normal larvae. Wings discs from early third instar wild-type larvae injected into late second or early third instar mutant larvae grow almost as much as control wild-type discs injected into wild-type larvae. These discs can differentiate when injected into metamorphosing larvae.