Hydrachna processifera Koenike, 1903

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 : 49

Hydrachna processifera Koenike, 1903

Syn.: Hydrachna perpera Koenike, 1908 , nov. syn.

Material examined: Hydrachna perpera , holotype female, SMNH 952, Leipzig ( Germany); Italy, Sicilia I 8, I 538, 1/0/2; Sardegna I 351, Lago Baratz, 0/0/1 ( Gerecke 1991); I 390, Flumendosa at Villasalto, 1/3/0 (new record); Hydrachna vaillanti K. Viets holotype male SMF 7160, Algeria, Sahara central, coll. Vaillant.

Discussion: The original description of H. perpera reports the presence of two paired small dots, but without detail about their location. In the type specimen (mounted in toto, with details of the frontal area hardly visible) these sclerites can be identified as the muscle attachment sclerites located medially from the postocularia. The gnathosoma is mounted in transverse position, but it is clear that the gnathosomal rostrum is not particularly elongated and that the palp segments are rather robust. From all points of view, this specimen agrees with H. processifera and should be treated as a junior synonym of that species. This point of view is corroborated by the fact that it was recorded occurring together with H. inermis , possibly a further synonym of H. processifera (see there).

Hydrachna vaillanti K. Viets, 1951 is very similar to H. processifera from most points of view (shape of frontal sclerites, coxae and palp ­ the chelicerae are missing). A possible diagnostic difference is found in the male genital field (minor in dimensions, anterior indentation more elongated, extending over 1/3 of the genital field L). This difference might be an individual aberration. The taxonomic state of H. vaillanti should be clarified with a study of population variability.