A detailed examination of thedistribution of EcollacZ^per.P expressing cells within the adult brain wasmade. Expression was detected in the ocelli, the photoreceptor cells, andthroughout the central brain and the optic ganglia. The detailed locationsof expressing cells were described. The EcollacZ distribution patternmatches the pattern of per protein expression qualitatively but therelative expression levels in different cells does not always correspond.Double staining with an antibody to elav which recognizes only neuronswas used to determine the nature of the EcollacZ^per.P staining cells. Thecells in the ocelli and eyes, the lateral cells, and the dorsalmost cortexcells were shown to be neurons. The staining cells located at the marginsof the cortex and neuropil in the optic lobes and the central brain, thecells within the lamina and central brain neuropil, and the cells in theinner chiasm are not neurons and are thought to be glia.