The diagnostic characters are reassessed and defined for the genera Lychas C. L. Koch, 1845, Mesobuthus Vachon, 1950, and Olivierus Farzanpay, 1987 (the latter is restored from synonymy with Mesobuthus). Four new genera are described: Aegaeobuthus gen. n. (type species Buthus gibbosus Brullé, 1832), Afrolychas gen. n. (type species Isometrus burdoi Simon, 1882), Janalychas gen. n. (type species Lychas srilankensis Lourenço, 1997), and Spelaeolychas gen. n. (type species Isometrus hosei Pocock, 1891). Type species are designated for subgenera Lychas (Distotrichus) Tikader & Bastawade, 1983 (type species Isometrus nigristernis Pocock, 1899), Lychas (Alterotrichus) Tikader & Bastawade, 1983 (type species Scorpio mucronatus Fabricius, 1793), and Lychas (Endotrichus) Tikader & Bastawade, 1983 (type species Isometrus scaber Pocock, 1893). All these three subgenera are now in synonymy with Lychas C. L. Koch, 1845. Lychas kaimana Lourenço, 2011 is synonymized with Lychas shelfordi (Borelli, 1904). Taxonomic position of Lychas timorensis Lourenço, 2018, which is a member of Lychas variatus (Thorell, 1876) complex, is discussed. The species and subspecies of Mesobuthus Vachon, 1950 are discussed, with seven subspecies elevated to species level: Mesobuthus afghanus (Pocock, 1889), stat. n., M. bogdoensis (Birula, 1896), stat. n., M. haarlovi Vachon, 1959, stat. n., M. iranus (Birula, 1917), stat. n., M. mongolicus (Birula, 1912), stat. n., M. persicus (Pocock, 1899), stat. n., and M. thersites (C. L. Koch, 1839), stat. n. Taxonomic changes are supported by 182 figures including the first published photographs of the syntypes of Olivierus hainanensis (Birula, 1904), stat. n., comb. n. and O. przewalskii (Birula, 1897), comb. n.

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