Little is known about clock-controlled output processes in Drosophila glia. In the lamina of the fly visual system, glial cells show rhythmic changes in volume coordinated with the volume changes in the photoreceptor-contacting interneurons (Gorska-Andrzejak, 2013). These rhythmic changes in structure coincide with the rhythmic expression of the α-subunit of the sodium pump, Na+/K+-ATPase, which is in high abundance in glia and its rhythmic expression is per-dependent, as per01 mutants lack rhythmic expression of this subunit (Gorska-Andrzejak et al., 2009). A recent study implicates glial cell oscillators in the control of Gclc, a rhythmically expressed component of the rate-limiting enzyme in glutathione synthesis (Chow et al., 2016). This study reported that pan glial knockdown of the circadian clock gene cycle via loco-GAL4>cycRNAi was sufficient to significantly decrease rhythmicity of Gclc expression (Chow et al., 2016).