Larval stages ofA. simplex(Rudolphi, 1809, det. Krabbe, 1878) andP. decipiens(Krabbe, 1878), infecting marine teleosts from New Zealand waters are described and compared morphometrically to pre‐adult and adult stages.A. simplexlarvae were positively identified using adults obtained from in vitro cultivation. Some morphometric variations compared to overseas descriptions are noted; the main differences being the small size ofA. simplexlarvae and the long intestinal caecum inP. decipienslarvae and adults from New Zealand waters.