A second group of prominent neuropil glia are astrocytes which were visualized via alrm-GAL4 driver (Doherty et al., 2009) combined with UAS-GFP. Interestingly, it appears that alrm-GAL4 marked as GFP-positive the same giant glial cells in the medulla that were also labeled via ensheathing glia NP6520-GAL4 driver. PER was again detected in these cells at ZT22 (Figures 6A,B) with the average signal lower in old flies (not shown). This suggests that these cells share features of both ensheathing and astrocyte glial cells.