Is the Japanese Oribatid Mite Euphthiracarus foveolatus Aoki, 1980 (Acari: Euphthiracaridae) a Junior Synonym of E. cribrarius (Berlese, 1904)?

Abstract

Two similar species of oribatid mites, Euphthiracarus foveolatus and E. cribrarius, have different distributions, with the former being endemic to Japan and the latter being a widespread Eurasian species that has not been reported from Japan. Recently the distinction between these species has become questionable, due to a mistake discovered in the original description. Also, new collections of E. foveolatus from Japan have shown it to be variable in morphology, and this variability overlaps in some ways with that of European populations of E. cribrarius.
In this paper, we examine the morphological variability of E. foveolatus and reconsider its distinctness from E. cribrarius, which seems to be its closest relative. Studied specimens of the latter were from Norway, the type country. Despite some overlapping characters, the Japanese and Norwegian specimens are distinguishable in two obvious ways. First is the ratio of lengths of aggenital setae (ag₁/ag₂); that of E. foveolatus is five or more times greater than the ratio in E. cribrarius. Second is that E. foveolatus lacks three leg setae that are present in E. cribrarius: one unnamed seta on tarsus II, v' on genu III and v' on genu IV. Thus, we feel these species are distinct and the names are not synonyms.