(A) Representative confocal images of stage 17 embryonic heads highlighting the expression of Dfd (purple), Myosin in muscles (blue) and FasII in axonal projections (green) in control (elav>RFP) animals and in animals with reduced Dfd expression in neurons (elav>DfdRNAi) or in muscles (Mef2>DfdRNAi) or both in both tissues (elav;Mef2>DfdRNAi). The single channels for the projections (FasII staining) of MN2a and/or MN3 to the MHE, MHD or LR muscles of an early stage 17 Drosophila embryo are shown. Asterisks highlight the location of MN2a and MN3, respectively. MN2a is identified by the FasII expressing axonal projection emerging from a Dfd expressing MN, which normally innervates the Dfd expressing MHE muscle (as shown in the elav>RFP control), while MN3 is identified as the MN underneath MN2a, which normally innervates the MHD muscle (as shown in the elav>RFP control). The panel on the right side represents a schematic drawing of the confocal image shown on the left side, summarizing the innervation of the anterior muscles (LR, MHE, MHD) by projections emerging from MN2a (magenta) or MN3 (cyan) in control and perturbation conditions. 