The arrenurid water mites of Madagascar (Acari, Hydrachnidia, Arrenuridae)

A survey is given of the arrenurid water mites recorded from Madagascar. While former data published in bibliography derive mostly from standing waters, we include here numerous new records mainly from springs and running waters, collected in 2001 and 2011. A new genus, Volobibikely gen. nov., is defined for Volobibikely primum sp. nov., a species from a spring in Central Madagascar. A total number of 18 further new species is described, 17 in the genus Arrenurus: Arrenurus (Arrenurus) ambrensis sp. nov., A. (Arrenurus) bispatulatus sp. nov., A. (Arrenurus) crenophilus sp. nov., A. (Brevicaudaturus) tandroka sp. nov., A. (Megaluracarus) ambohitra sp. nov., A. (Megaluracarus) concavoides sp. nov., A. (Megaluracarus) felix sp. nov., A. (Megaluracarus) uncipetiolatus sp. nov., A. (Micruracarus) aethes sp. nov., A. (Micruracarus) brunneus sp. nov., A. (Micruracarus) dobomponina sp. nov., A. (Micruracarus) mandrarensis sp. nov., A. (Truncaturus) cuspidipes sp. nov., A. (Truncaturus) delocercus sp. nov., A. (Truncaturus) gigas sp. nov., A. (Truncaturus) porphyrus sp. nov., A. (Truncaturus) riparius sp. nov.; and one in the genus Wuria, W. ferrumequorum sp. nov. The female of Arrenurus geniculatus Koenike, 1898 is described for the first time. Arrenurus (subgen.?) vigorans Koenike, 1898, described from a deutonymph, is considered a ‘species incerta’.
Arrenurus (A.) capensis Thor, 1902, previously known from continental Africa, is reported for the first time from Madagascar. New geographical records are given for the already known species Arrenurus (A.) dentifer Lundblad, 1946, A. (A.) frustrator Koenike, 1898, A. (A.) obliquus Koenike, 1898, A. (A.) rudiferus Koenike, 1898, A. (A.) geniculatus Koenike, 1898, A. (A.) voeltzkowi Koenike, 1898, and Wuria milloti Gerecke, 2004. In total, the number of arrenurids known from Madagascar grows from 23 to 43 species (not taking in consideration the females ‘incertae sedis’ mentioned in the following).
A survey is given of the documentation of Madagascan arrenurids. As large parts of the island are still completely uninvestigated, large numbers of undescribed species can still be expected. Additional females recorded as singletons from various parts of the island, probably representatives of further distinct species, are briefly characterized. They could belong to species known in the male sex only, or species new to science. A key is presented for all known arrenuroid species from Madagascar.