Svalbard is a singular region to study biodiversity. Located at a high latitude and geographically isolated, the archipelago possesses widely varying environmental conditions and unique flora and fauna communities. It is also here where particularly rapid environmental changes are occurring, having amongst the fastest increases in mean air temperature in the Arctic. One of the most common and species-rich invertebrate groups in Svalbard is the mites (Acari). We here describe the characteristics of the Svalbard acarofauna, and, as a baseline, an updated inventory of 178 species (one Ixodida, 36 Mesostigmata, 43 Trombidiformes, and 98 Sarcoptiformes) along with their occurrences. In contrast to the Trombidiformes and Sarcoptiformes, which are dominated in Svalbard by species with wide geographical distributions, the Mesostigmata include many Arctic species (39%); it would thus be an interesting future study to determine if mesostigmatid communities are more affected by global warming then other mite groups. A large number of new species (42 spp.) have been described from Svalbard, including 15 that have so far been found exclusively there. It is yet uncertain if any of these latter species are endemic: six are recent findings, the others are old records and, in most cases, impossible to verify. That the Arctic is still insufficiently sampled also limits conclusions concerning endemicity.

Here we present the first records of Denheyernaxoides from North America: D. americanus, collected from coniferous litter, soil, and moss in Nova Scotia, Canada. These new records significantly expand the known distribution of the species. Denheyernaxoides americanus is redescribed to include Canadian specimens and to rectify discrepancies in the species’ description identified during examination of the holotype. The deutonymph of D. americanus is also described. Sequences, representing a 658 bp region of the mitochondrial cytochrome c oxidase subunit I (COI), were obtained from representative specimens collected in Canada. Comparison of these sequences with those from the Barcode of Life database (BOLD) suggests that a second species of Denheyernaxoides may occur in British Columbia, Canada. A revised key to world species of Denheyernaxoides is provided.