Schematic representation of Notch reporter E(spl) mδ0.5 expression during photoreceptor differentiation. Expression is initiated in R3 and R4 of the 5-cell pre-cluster and becomes restricted to R4 as Notch activity resolves. Light orange indicates photoreceptors with R3 in light green and R4 in dark green. MF marks the morphogenetic furrow, boxed region indicates the region shown in B. 