Redescription of Dermacentor everestianus Hirst (Acari: Ixodidae), a parasite of mammals in mountains of China and Nepal with synonymization of D. abaensis Teng and D. birulai Olenev.

Examination of extensive Dermacentor Koch, 1844 holdings stored in several major tick collections allowed us to re-evaluate the taxonomic content of Dermacentor everestianus Hirst, 1926 and redescribe all of its parasitic stages in detail for the first time. Examination of the type specimens of Dermacentor abaensis Teng, 1963 , a species treated as valid by most workers, and Dermacentor birulai Olenev, 1927 , a species some recent authors considered as valid, led us to the conclusion that they are junior synonyms of D. everestianus. The relation of D. everestianus with some other species in the genus is questionable and warrants further studies. From possibly sympatric Dermacentor species, the adults of D. everestianus can be distinguished by the following combination of characters: intensive ivory colored ornamentation of conscutum and scutum, absence of brown patches on lateral fields of conscutum in the male, long and narrow dorsal prolongation of spiracular plates, short cornua, short dorsal spur on trochanter I, and absence of large ventral spur on distal ends of genua and tibiae II-IV. Nymphs of D. everestianus can be distinguished by numerous setae on alloscutum (>48 pairs), large spiracular plates with their longitudinal diameter exceeding that of sclerotized ring around anal valves, moderate lateral projections of basis capituli with blunt apices situated slightly posterior to the midlength of basis capituli dorsally, relatively large auriculae, relatively short, narrowly rounded at apices spurs on coxae I with internal spur being shorter than external and moderate triangular spur on coxae IV; while larvae can surprisingly easily be distinguished from those of other species found in the region by greatly elongated posterior portion of scutum where eyes are situated just posterior to the midlength of scutum. So far, D. everestianus is found only in China and Nepal, where the adults were collected from domestic and wild ungulates while the immature stages were recorded from lagomorphs and rodents.