Figure 1: Schematic representation of development of the nervous system in the third instar Drosophila larval brain. During postembryonic neuroblast development, the brain of Drosophila can be divided into the paired optic lobes (OL) at the lateral surface of the two hemispheres, the central brain (CB), located medially to the OL, and the ventral nerve cord (VNC). The type I neuroblasts are the most abundant in the CB and VNC. The type II neuroblasts are located on the dorsomedial surface of the hemispheres.