A new mite species Fagacarus absalom sp. n. (Astigmata: Acaridae) from the Eastern Palearctic, with 18 rRNA molecular barcodes

The genus Fagacarus (Acari: Acaridae) characterized by long pectinate dorsal setae and heavily sclerotized and ornamented idiosoma is unmistakably recognizable in the subfamily Rhizoglyphinae. Mites of this genus live inside fallen tree trunks and have been only occasionally collected. However, it is increasingly likely that these mites are more widespread than previously believed. The single described species, Fagacarus verrucosus, is known from the USA (Indiana and Michigan); two undescribed species were reported from North America (Colorado) and the Western and Eastern Palearctic. The deutonymphal stage of Fagacarus is known, but it has never fully described. The paper presents description of a new species, Fagacarus absalom sp. n., based on adults and deutonymphs found in the Russian Far East. The new species differs from F. verrucosus by the length of seta d IV (female) and solenidia (σ II) of legs, the shape of posterior apodemes II in adults and pseudanal setae ps1-2 and the dorsal crista of tarsus IV in males. The uncorrected 18S rDNA genetic distance between F. absalom sp. n. and F. verrucosus is 1.52%, which is sufficient to delimit the two species based on this slowly evolving nuclear gene.