Hemizygous embryos hatch with normal cuticles. No transformation of anterior segments toward abdominal segment A8 is seen. These larvae are smaller than wild-type and attain the second instar with approximately a 24 hour delay. Most of the larvae die several days later without undergoing a second moult. All the major imaginal discs are smaller than in wild-type larvae. Almost all second instar larvae have melanotic pseudotumours. Areas of melanisation are seen touching the imaginal hindgut ring and hindgut. Mitotic figures and metaphase chromosome morphology of larval brain squashes do not show striking anomalies.
Homozygotes die as first or second instar larvae. mxcG9/mxc22a-6 females lay many small eggs with a thin chorion and small dorsal appendages that collapse after oviposition. mxcM1/mxcG48 females have reduced viability and do not lay eggs. Some egg chambers contain the normal number of nurse cells, but oogenesis appears arrested before stage 7-8. Egg chambers degenerate in older flies. mxcG46/mxcG48 females have reduced viability, rudimentary gonads and do not lay eggs. The sheaths of the somatic cells that organise the ovarioles are still present and all structures derived from genital imaginal disc appear similar to wild-type.
Homozygotes die at the embryonic/larval interface. Most mxcG48 heterozygotes with mxc1 or mxcSO die in the third instar with blood cell tumors.