No mnd¹/mnd³⁵ animals are found after the 2nd to 3rd instar larval stages. Strong allele. In mutant brains, the ventral ganglion is slightly smaller than that of wild-type. The brain lobes of the mutants are severely reduced (less than 50% of the diameter of wild-type brain lobes).

Homozygous larvae never form puparia. Mutant larvae have smaller imaginal discs than normal (the maximum size is larger than the size of wild-type late second instar discs but smaller than the size of wild-type young third 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 decrease in size for the first 3 days, after which they are no longer detectable. Mutant cells are found in structures derived from all the imaginal discs in mixtures of wild-type and mutant embryonic cells cultured in vivo and then transplanted into larvae. Wings discs from early third instar wild-type larvae injected into late second or early third instar mutant larvae show reduced growth compared to control wild-type discs injected into wild-type larvae. These discs can differentiate when injected into metamorphosing larvae.