Observed in two clusters of cells, one in each brain hemisphere towards the optic precursor region at the first instar larval stage. By third instar stage, very strong expression is seen in the inner optic focus, which extends laterally as a stripe toward the outer optic anlagen. Strong expression is seen in clusters of cells in the central brain and the subesophageal ganglion. Moderate expression levels are seen along the margin of the ventral ganglion.

Strong expression of ScerGAL4^SG26.1 is detected in the larval optic focus in 0hrs APF pupal brains, which is seen to expand by 6hrs APF, with strong expression in the inner optic anlage. At 0hrs APF, ScerGAL4^SG26.1 is expressed in a few clusters of cells located in the central brain. By 13hrs APF the expression domain in the inner optic anlage enlarges, particularly towards the outer optic anlage, and the small clusters of cells in the central brain continue to express ScerGAL4^SG26.1. By 24hrs APF ScerGAL4^SG26.1 is expressed in the developing medulla and lamina plate, and becomes more intense by 63hrs APF but reduces by the end of pupation.