Fig. 3. DiI staining of the psc neurone. (A) Central projections of the psc neurone in an untreated specimen. The neurone is formed by a single robust axon (arrowheads) entering the CNS via the dorsal wing nerve and exhibits the stereotypical features previously described for this neurone. (B) The psc neurone following unilateral ablation of the dorsal and lateral groups of sensory neurones. The neurone shows disruption to its structure at the point of entry (black arrow), as well as repeatedly crossing the midline (arrowheads) to form the posterior process (white arrows). (C) An unusual example of the psc neurone central projection following unilateral ablation of dorsal and lateral clusters. In this example, the psc has entered the CNS ectopically via the metathoracic nerve (arrows) and has formed an elaborate central projection in which elements of the normal psc projection can be recognised. Scale bar: 30 µm.