The taxonomic status of the water mite genera Todothyas Cook and Parathyas Lundblad – supplement to Di Sabatino et al. (2009)

The taxonomic placement of Parathyas Lundblad, 1926 as a separate monotypic genus was questioned by Tuzovskij (2007) who demonstrated the absence of significant apomorphic character states in larvae and arranged the type species in the genus Thyas Koch, 1836. Özdikmen (2006) reported on the homonymy of Thyas Koch, 1836 ["1835", err. Özdikmen] with Thyas Hübner, 1824 (Lepidoptera), and proposed Acerbitas nom. nov. for Thyas Koch, 1836. However, he incorrectly applied the rules of the International Code of Zoological Nomenclature: as stated by Di Sabatino et al. (2009), if this taxon is maintained separate from Parathyas, the first available name for Thyas Koch, 1836 is Todothyas COOK, 1974. Considering that there are no significant differences in larval and adult morphology - dorsal setae on P-4 of adults, for Di Sabatino et al. (2009, p. 4) the main reason to distinguish Parathyas from Todothyas, may also be found in Todothyas bruzelii and T. pachystoma (see Tuzovskij 2007) - there is no evidence to accept the taxonomic placement of the two taxa as separate units. Therefore, due to preoccupation of the name Thyas, all water mite species previously attributed to this genus have now to be placed under Parathyas. In this scenario, Parathyas displays a rather wide variability of characters states, with Parathyas thoracata (Piersig, 1896), P. primitiva (Lundblad, 1934) from India, and P. suber (Gerecke, 1996) from Andalusia differing from other species in the presence of variously-shaped frontal shields (Di Sabatino et al. 2009), but probably not forming a monophyletic species group. The puzzle-like pattern of character combinations among species of the genus does furthermore not support a subgeneric subdivision on the base of fusion, or not, of acetabula 2+3 to the medioposterior genital flap margins. As first proposed, with a question mark, by K.O.Viets (1987), and then confirmed, but without an explicit statement, by Tuzovskij (2007), no subgenera can be accepted within the former genus Thyas. Thyas Koch, 1836, Todothyas Cook, 1974 and Acerbitas Özdikmen, 2006 are synonyms of Parathyas Lundblad, 1926. Finally, Di Sabatino et al. (2009, p. 22) erroneously reported “Sperchon (Hispidosperchon) hibernica Halbert, 1944” instead of Sperchon (Hispidosperchon) hibernicus Halbert, 1944.