Fig. 3. Late expression of scute (sc) and asense (ase) in the pupal thorax of Calliphora vicina. After fusion of the two heminota along the midline, sc is re-expressed in the pupal thorax 29 hours after pupariation. Expression is initially widespread, and is excluded only from the sites of the prospective sutures, before becoming restricted to individual microchaete precursors by 31 hours after pupariation (A). scute is re-expressed in the macrochaete precursors (B: enlargement of the boxed area in A; macrochaete precursors are indicated by arrowheads) in the immediate vicinity of which down-regulation of sc in neighbouring cells is particularly clear. By 33 hours after pupariation, ase expression can be detected in microchaete precursors (C), and by 51 hours after pupariation, 22C10 staining reveals that axonogenesis has been initiated (D).