Expression of Ubx in the ventral CNS of first instar and late third instar larvae. (A) Dorsal projection showing Ubx expression (red) in parasegments (PS) 5 and 6. (A’) Transverse projection at the indicated level in PS6. (B,C) Optical sections at the level of the adult-specific lineages (B) and of the larval neurons (C). (B’) Transverse projection showing the level of the optical sections and the uniform expression in the larval neuron layer around the neuropil (np) and the variable staining of the adult-specific lineages. Blue: elav; np: neuropil; PS: parasegment; Ubx: Ultrabithorax.