Cover legend: Giant fiber neurons of Drosophila melanogaster injected with Lucifer yellow (magenta) and Neurobiotin (blue), in animals with GFP expression in auditory axons driven by the engrailed gene (green). Neurobiotin is retrogradely transferred across gap junctions from the giant fiber into a subset of the auditory axons (cyan). Perturbation of engrailed leads to changes in synaptic connectivity. Below are shown heads of animals with engrailed-driven GFP expression. For more details, see the article by Pézier et al. (pages 11691–11704).