Genus Hydrogamasus Berlese, 1892 Hydrogamasus Berlese, 1892c: 5. Hydrogamasus.— Vitzthum, 1931a: 142; 1943: 756; Baker & Wharton, 1952: 73; Ryke, 1962b: 160; Hirschmann, 1966b: 7; Lee, 1970: 64. Hydrogamasus (Hydrogamasus).— Hirschmann, 1966b: 10. Type species: Gamasus littoralis G. & R. Canestrini, 1881, by subsequent designation (Berlese, 1903a). Berlese (1892c) described the genus Hydrogamasus to include two species, Gamasus littoralis G. & R. Canestrini, 1881 and H. giardi (Berlese & Trouessart, 1889). Berlese (1903a) then designated G. littoralis as the type species of Hydrogamasus. However, Oudemans (1902b) felt that G. littoralis was a junior synonym of G. salinus Laboulbene, 1851. Vitzthum (1943), Baker & Wharton (1952), and Ryke (1962b) also said that G. littoralis is a junior synonym of G. salinus. Lee (1970) then found that G. littoralis is not a synonym of G. salinus. He placed G. littoralis in the Ologamasidae as the type species of Hydrogamasus, and G. salinus in Pergamasus (Parasitidae). Oudemans (1936, page 163) also found that G. salinus was correctly placed in Pergamasus. The type species of Hydrogamasus is therefore Gamasus littoralis, as originally designated by Berlese (1903a).

Published as part of Castilho, Raphael C., Silva, Edmilson S., De, Gilberto J. & Halliday, Bruce, 2016, Catalogue of the family Ologamasidae Ryke (Acari: Mesostigmata), pp. 1-147 in Zootaxa 4197 (1) on page 84, DOI: 10.5281/zenodo.168445