Hydrachna denudata Piersig, 1896

Davids, Kees, Sabatino, Antonio Di, Gerecke, Reinhard, Gledhill, Terence & Smit, Harry, 2005, On the taxonomy of water mites (Acari: Hydrachnidia) described from the Palaearctic, part 1: Hydrachnidae, Limnocharidae and Eylaidae, Zootaxa 1061, pp. 36-64 : 40

Hydrachna denudata Piersig, 1896

Species incerta

Discussion: The holotype female of this species (locus typicus: Germany, Leipzig, Großzschocher) is missing. The original description, without illustrations, does not provide useful information on diagnostic characters. Figures published in the literature ( Koenike 1909, K. Viets 1936, Sokolow 1940, several illustrations published later copied after these authors) are based only on a slide in the collection of Koenike (now lost, erroneously cited as " Hydrachna denudata Koen. [...] Koenikes Type, Prp. 942" by K.Viets 1936, p. 60) and on a specimen from Russia deposited at ZISP; a description of the deutonymph was given by Láska (1955). All records of adult specimens published since the first description from Central Europe (exclusively females) are not documented in museum collections. K.Viets (1936) attributed to this species the following combination of diagnostic characters: integument with pointed papillae; frontal area lacking sclerite platelets; medial margins of Cx­3/4 forming an obtuse angle; lateral eye capsules with a short and large medial apodeme; gnathosomal rostrum strongly curved and by far longer than the base. However, following Sokolow (1931), in the frontal area both pre­ and postocularia are associated with sclerite platelets. In view of the lack of a type specimen, there is no chance for resolving the problems of dissenting interpretations. Therefore the species must be considered a species incerta.