EN
Platytrombidium fasciatum (C. L. Koch, 1836) and Atractothrombium sylvaticum (C. L. Koch, 1835) are redescribed. Characteristics of larvae, deutonymphs and adults as well as the data on biology are provided. The status of Atractothrombium Feider, 1952, earlier synonymized with Platytrombidium Thor, 1936, is restored, based on the characters discovered in larvae and postlarval forms. The revised diagnoses of both genera are proposed. Data on habitat specificity, phenology, developmental times and parasitic associations of larvae are given. Females of P. fasciatum and A. sylvaticum from which larvae were obtained by experimental rearing, are designated as neotypes. Platytrombidium ornatum (Kramer, 1896) syn. nov., P. insulanum (Oudemans, 1901) syn. nov., P. vagabundium (Berlese, 1903) syn. nov., P. trispinum (Berlese, 1910) syn. nov., P. quadrispinum (Berlese, 1910) syn. nov. and P. albofasciatum (Berlese, 1912) comb. nov. are considered synonyms of Platytrombidium fasciatum (C. L. Koch, 1836). Atractothrombium simulans (Berlese, 1910) comb. nov. and Cylindrothrombium arnolfi Haitlinger, 1998 syn. nov. are considered synonyms of Atractothrombium sylvaticum (C. L. Koch, 1835). Thrombidium [sic!] tectocervix (Oudemans, 1903) (originally described as Hydrarachna [!]) is transferred to Atractothrombium. Platytrombidium belairense Gabryś, 1999 syn. nov. is regarded as objective junior synonym of Foliotrombidium ornatum Womersley, 1945. Generic affiliation of Empitrombium littorale (Michener, 1946) and E. dictyostracum (Vercammen-Grandjean and Cochrane, 1974) is maintained. Cylindrothrombium Feider, 1955 is retained a synonym of Platytrombidium Thor, 1936.