In the juliform millipede Nopoiulus kochii (Gervais, 1847) (Blaniulidae), the eighth and the ninth pair of trunk appendages are typical legs since their first appearance in the III post-embryonic instar and so remain in the IV instar (A, D, G), and only turn into short, scale-like appendages with the moult to the V instar (B, E, H). With a further moult, the millipede, now in its VI post-embryonic instar, becomes an adult with two pairs of bulky, complex gonopods (C, F, I). (A-C) External morphology. SEM, scale bar 300 μm. (D-F) Esoskeletal and endoskeletal components. Projection at maximum intensity of serial pictures collected with Confocal Laser Scanning Microscope, soft tissues digested with KOH 10%, cuticle stained with Blue Evans 0.005%, scale bar 200 μm. (G-I) Internal anatomy. Para-midsagittal paraffin sections (7 μm), Mallory's triple stain, scale bar 200 μm. Arrow pairs point to the eighth and ninth pair of trunk appendages, as walking legs (A, D, G) or scale-like appendages (B, E, H).