Definition of callunae species group in the genus Stigmaeus (Acari: Prostigmata: Stigmaeidae) with description of a new species from Russia and preliminary molecular phylogeny based on COI sequences

The callunae species group of Stigmaeus (Acari: Stigmaeidae) is created for 14 species. The female and male of S. crypticus sp. nov. are described from Western Siberia and Ural. The female of Stigmaeus callunae Evans, female and male of S. macroposbus Liang and Hu are recorded from Russia for the first time and redescribed based on material from Russia. Stigmaeus burjaticus Khaustov is considered a suspected junior synonym of S. longisetosus Liang and Hu; S. boshroyehensis Khanjani et al. and S. ayyildizi Dönel and Doğan are suspected junior synonyms of S. creber Barilo; S. pseudoangustus Stathakis et al. is suspected to be a junior synonym of S. angustus Dönel and Doğan. A preliminary phylogenetic analysis based on COI sequences is conducted for the first time on 21 Palaearctic species of Stigmaeus. A key to species of callunae species group is also provided.