Hydrachna is a genus of mites in the family Hydrachnidae, the sole genus of the family. There are more than 80 described species in Hydrachna. Larvae of this genus are known to be parasites of water beetles such as Eretes griseus by attaching to the back of the thorax and abdomen. These water mite larvae are also hosts of Callicorixa, Corixa, Cymatia and Sigara species, although Sigara falleni has been described as "immune" to these mites, and Cymatia coleoptrata and Sigara striata also gain this "immunity" after a few years of interaction.
Species
These 87 species belong to the genus Hydrachna:
- Hydrachna analis <small>Viets & K.</small>
- Hydrachna approximata <small>Halik, 1940</small>
- Hydrachna baculoscutata <small>Crowell, 1960</small>
- Hydrachna batorligetiensis <small>Szalay, 1953</small>
- Hydrachna bilobata <small>Halik, 1940</small>
- Hydrachna bimaculata <small>Koenike</small>
- Hydrachna bisignifera <small>Viets & K.</small>
- Hydrachna brehmi <small>Szalay, 1955</small>
- Hydrachna bulgarensis <small>K.Viets, 1940</small>
- Hydrachna canadensis <small>Marshall, 1929</small>
- Hydrachna comosa <small>Koenike, 1896</small>
- Hydrachna conjecta <small>Koenike, 1895</small>
- Hydrachna conjectoides <small>Lundblad, 1947</small>
- Hydrachna cordata
- Hydrachna crenulata <small>Marshall, 1930</small>
- Hydrachna cronebergi <small>Koenike, 1897</small>
- Hydrachna cruenta <small>Muller, 1776</small>
- Hydrachna curtiscutata
- Hydrachna danubialis <small>Laska, 1964</small>
- Hydrachna denudata <small>Piersig, 1896</small>
- Hydrachna distincta <small>Koenike, 1897</small>
- Hydrachna dorsoscutata <small>Viets & K.</small>
- Hydrachna eugeni <small>K.H.Viets, 1911</small>
- Hydrachna extorris <small>Koenike, 1897</small>
- Hydrachna geographica <small>Muller, 1776</small>
- Hydrachna georgei <small>Soar, 1908</small>
- Hydrachna globosa <small>(De Geer, 1778)</small>
- Hydrachna goldfeldi <small>Thor, 1916</small>
- Hydrachna guanajuatensis <small>Cook</small>
- Hydrachna halberti <small>Soar, 1908</small>
- Hydrachna hamata <small>Lundblad, 1947</small>
- Hydrachna hesperia <small>Lundblad, 1934</small>
- Hydrachna heterophthalma <small>Viets & K.</small>
- Hydrachna hormuzakii <small>Husiatinschi, 1937</small>
- Hydrachna hungerfordi <small>Lundblad, 1934</small>
- Hydrachna hutchinsoni <small>Lundblad, 1934</small>
- Hydrachna incognita <small>(Wainstein, 1976)</small>
- Hydrachna inermis <small>Piersig, 1895</small>
- Hydrachna inversa <small>Walter, 1927</small>
- Hydrachna juncta <small>Walter, 1926</small>
- Hydrachna laceriscuta <small>Lundblad, 1941</small>
- Hydrachna leegei <small>Koenike</small>
- Hydrachna levigata <small>Koenike, 1897</small>
- Hydrachna levis <small>Williamson, 1913</small>
- Hydrachna linderi <small>Lundblad, 1947</small>
- Hydrachna longiscutata
- Hydrachna lupus <small>Wainstein, 1976</small>
- Hydrachna magniscutata <small>Marshall, 1927</small>
- Hydrachna marita <small>Wainstein, 1966</small>
- Hydrachna marshallae <small>Lundblad, 1934</small>
- Hydrachna microscutata <small>Marshall, 1929</small>
- Hydrachna miliaria <small>Berlese, 1888</small>
- Hydrachna miyazakii <small>Uchida, 1937</small>
- Hydrachna multipora <small>Cook, 1967</small>
- Hydrachna mysorensis <small>Cook, 1967</small>
- Hydrachna mystomirabilis <small>Habeed, 1954</small>
- Hydrachna neocaledonica <small>Smit, 2002</small>
- Hydrachna nonlamellata <small>Viets & K.</small>
- Hydrachna novaehollandica
- Hydrachna oculoscutata <small>Smit, 2002</small>
- Hydrachna orientalis <small>Thon, 1905</small>
- Hydrachna paludosa
- Hydrachna palustris <small>Smit, 1992</small>
- Hydrachna papilligera <small>K.H.Viets, 1919</small>
- Hydrachna perpera <small>Koenike, 1908</small>
- Hydrachna piersigi <small>Koenike, 1897</small>
- Hydrachna processifera <small>Koenike, 1903</small>
- Hydrachna queenslandica
- Hydrachna rectirostris <small>Viets & K.</small>
- Hydrachna rhopaloidea <small>K.H.Viets, 1942</small>
- Hydrachna rotunda <small>Marshall, 1930</small>
- Hydrachna rubicunda <small>K.H.Viets, 1930</small>
- Hydrachna schneideri <small>Koenike, 1895</small>
- Hydrachna similans <small>Marshall, 1928</small>
- Hydrachna simulans <small>Marshall, 1928</small>
- Hydrachna sistanica <small>Pesic, Smit & Saboori, 2012</small>
- Hydrachna stipata <small>Lundblad, 1934</small>
- Hydrachna tasmanica <small>Lundblad, 1947</small>
- Hydrachna tchadensis <small>Smit, 1994</small>
- Hydrachna tenuissima <small>Viets, 1935</small>
- Hydrachna testudinata <small>Cook</small>
- Hydrachna trilobata <small>Viets & K.</small>
- Hydrachna triscutata <small>Lundblad, 1947</small>
- Hydrachna valida
- Hydrachna ventrifissa <small>Viets & K.</small>
- Hydrachna vulpes <small>Wainstein, 1976</small>
- Hydrachna williamsoni <small>Soar, 1908</small>
References
Further reading