Abstract
A study published in 2016 reported on an undescribed species of Apatemon (Strigeidae) from New Zealand that was previously well known from its larval stages. Only a single specimen from a mallard duck was available at the time, which was described and given the provisional name Apatemon sp. "jamiesoni". Specimens also obtained from a spotted shag were not in good enough condition to form the basis of a new species description. A black-backed gull has since been discovered with specimens of this strigeid, their identity confirmed by genetic similarity, allowing formal description and naming of this species. This paper provides a description of the new specimens from the black-backed gull, along with a comparison with the specimens from other bird hosts, reprises some data from Blasco-Costa et al. (Parasitol Res 115:271-289, 2016) and presents formally the name Apatemon jamiesoni n. sp. This species differs from all other species of Apatemon in its small size, particularly that of the ovary and testes. It is most similar to A. jamesi from which it differs in the size of the oral and ventral suckers.