A new vagrant eriophyoid mite species, Setoptus tsugivagusn. sp. Chetverikov (Eriophyoidea, Phytoptidae, Nalepellinae, Nalepellini), is described from the needles of the western hemlock, Tsuga heterophylla (Rafinesque) Sargent (Pinaceae) in Vancouver, Canada. The new species can be distinguished from all other members of Setoptus by a distinct pattern of several short longitudinal ridges on the posterior half of the prodorsal shield. Elements of the anal secretory apparatus (ASA) were observed in adults of S. tsugivagusn. sp., suggesting that the ASA is present in both major phylogenetic lineages of Eriophyoidea (Eriophyidae s. l. and Phytoptidae s. l.). Therefore, this structure could be a synapomorphy for all Eriophyoidea. We briefly discuss the function and morphological variety of the ASA in Eriophyoidea. D2 28S rDNA sequences of four nalepelline species were obtained: Boczekella reticulataBagnyuk 1987 (GenBank accession number MK124605), Nalepella tsugifoliaeKeifer 1953 (MK124606), Setoptus piniBoczek, 1964 (MK124607), and S. tsugivagusn. sp. (MK124608). Molecular phylogenetic analyses of D2 28S rDNA sequences of the mites of the subfamily Nalepellinae confirmed monophyly of the tribe Nalepellini and retrieved Setoptus and Nalepella as polyphyletic. Additionally, our data indicate that 28S rDNA sequence KF782472.1, previously reported to be Trisetacus ehmanni Keifer 1963 by Li et al. (2014), belongs to another species of the genus Trisetacus, possibly T. quadrisetus (Thomas), and the sequence KF782471.1, previously reported to be Trisetacus sp., might belong to T. juniperinus (Nalepa). We also discuss the systematics of nalepellines and their host association with conifers.