Mutant embryos show an overproduction of muscle founder cells.

Before delamination of the SI neuroblasts, medial, intermediate and lateral regions of the neuroectoderm can be detected in homozygous embryos. Only slight differences in cell size can be detected in the ventral neuroectoderm (VNE) compared to wild-type. However, morphological changes are visible in the basal regions of the VNE; in contrast to wild type, where only single basally enlarged cells can be detected, whole groups of cells become larger basally in homozygous embryos. The enlarged cells also do not shrink during stage 9 as occurs in wild-type embryos, rather more and more cells become enlarged until almost all cells of the VNE have increased in size and eventually become neuroblasts.

Single cells from wild-type embryos transplanted into the ventral neurogenic region of Df(3R)Delta-FX3 host embryos give rise to neural cells.

Heterozygotes show a 'delta' phenotype and confluence of wing veins 2 and 5.

Embryos exhibit few, if any, fused muscles. The unfused, birefringent fibres, have a random pattern of fine fibres apparently radiating out from small fragments of dorsal cuticle. The birefringent is clearly correlated with the expansion of the CNS and PNS, and the loss of epidermis and the degree to which myoblast fusion occurs. Where myoblast fusion fails conspicuous clusters of mesodermal cells are formed and if epidermal territories are expanded cells in these clusters may be recruited to fusion.

Homozygotes die as embryos. Surface of the CNS at 20 hours almost completely lacks investing cells. Islands of neural lamella and associated sheath cells are observed but no continuous barrier cell layer. There are few glial profiles among the abundant neuron cell bodies within the ganglion and among neurons in the neuropile.

Post-transcriptional control of AS-C expression is suppressed, all cells expressing RNA accumulate protein.

The expression of the Df(3R)Delta-FX3 phenotype is modified by the presence of ASC loss-of-function mutations.

Fusion of tarsal segments: 2-4 tarsal segments fuse together forming a single segment without boundaries visible.

Homozygotes die as embryos with an extreme embryonic neurogenic phenotype.