Homozygotes are sterile. Semi-lethal. Heteroallelic In(3)Msu¹/In(3)Msu² flies are recovered at 4% of the expected value. Male heteroallelic escapers are recovered at about 50% the rate of female escapers. Modifies the phenotype of w^a such that a mottled stripe of brilliant red at the posterior of the eye. In(3)Msu¹/In(3)Msu² escapers act as strong suppressors of w^a and also recessive enhancers of synaptic-dependent gene expression at w. Testes of w^a, In(3)Msu¹ also show increased pigmentation with respect to w^a. In(3)Msu¹/In(3)Msu² enhances the zeste effect of z¹, w^zl, producing white eyes, but has no effect on z¹, w^zm.

Homozygous lethal. Rare homozygous adult escapers display a rough eye phenotype. Adult retina and ocelli are devoid of photoreceptors. Pigment cell lattice has random distribution of pigment cells and interruptions to the pattern.