In nab^G26 embryos, thoracic neuroblast 3-3 (NB3-3T) shows delayed quiescence and prolonged proliferation. (This is also true of many other thoracic neuroblasts in mutant first instar larvae.) Consequently, NB3-3T generates additional EL neurons.

Homozygotes die as first to second instar larvae. The larvae appear uncoordinated, have slow muscle contractions and initiate fewer movements than wild type. nab^G26/Df(3L)GN19 animals die during the first to second larval instars. The larvae initiate fewer movements than normal and have slow muscle contractions. nab^G26/nab^A23 animals survive larval development, and most of them pupate. Most of the pupae eclose, although about 20% are unable to completely escape the pupal case and become trapped. The eclosed adults appear morphologically normal and show grooming behaviour. However, when they try to walk they are extremely uncoordinated and fall often, and if they land on their backs, a few of the adults are able to right themselves with considerable difficulty. The adults do not fly or jump and die within 24-48 hours of eclosion, presumably from an inability to feed. nab^e310/nab^G26 animals generally die during the first to second larval instar, although about 5% pupate. These pupae appear morphologically normal when examined outside the pupal case, but they never eclose, although weak movements are seen. Homozygous embryos lack 1-4 EL (eve lateral) neurons in a subset of abdominal segments. The mean number of EL neurons per abdominal hemisegment is 7.3 in homozygous embryos compared to 8.1 in wild-type embryos, and the number of abdominal hemisegments with less than 7 EL neurons is 17.94% in homozygous embryos, compared to 7.68% in wild-type embryos. Homozygous clones in the eye are moderately reduced in size compared to wild-type clones. Homozygous clones induced in a Minute background in the eye appear grossly normal and populate more than 80% of the eye.