Neuronal diversity is essential for the formation of complex and correct neuronal circuits. During brain development, various types of neuronal populations are produced from different progenitor pools to produce neuronal diversity that is sufficient to establish functional neuronal circuits. Thus, multiple progenitor pools produce different subsets of neuronal populations to contribute to the neuronal diversity. However, the molecular mechanisms that specify the identity of each progenitor pool remain obscure. Here, we show that Wnt signaling is essential for the specification of the identity of progenitor pools in the Drosophila visual center. In the medulla, the largest component of the visual center, different types of neurons are produced from two progenitor pools: the outer proliferation center (OPC) and glial precursor cells (GPC). However, we found that OPC-neurons are produced in the GPC at the expense of GPC-neurons when Wnt signaling is suppressed in the GPC. In contrast, GPCs are ectopically formed when Wnt signaling is ectopically activated; consequently, GPC-neurons are ectopically produced in the OPC. These results suggest that Wnt signaling is necessary and sufficient for the specification of identity of the progenitor pools. We also found that Homothorax (Hth), which is temporally expressed in the OPC, is ectopically induced in the GPC by suppression of Wnt signaling and that ectopic induction of Hth phenocopies the suppression of Wnt signaling in the GPC. Since β-catenin signaling specifies progenitor pool identity in the developing mammalian thalamus, evolutionarily conserved Wnt signaling may specify the identity of progenitor pools in mammalian and fly brains. .