Hydrochus elsjeae Makhan 1994: 40 Hydrochus obscurus Sharp Taxonomy of water beetles in the genus Hydrochus Leach, 1817, from Bolivia, Brazil and Paraguay (Coleoptera: Hydrochidae) Perkins, Philip D. Zootaxa 2021 2021-06-28 4994 1 1 93 3N67G Makhan Makhan 2021 [151,489,1683,1710] Insecta Hydrochidae Hydrochus Animalia Coleoptera 43 44 Arthropoda species elsjeae stat. nov.      Hydrochus elsjeae Makhan 1994: 40   Hydrochus obscurusSharp; Oliva (1996), incorrect synonymy by Oliva    Originallydescribed from Bolivia, based on one male. Only the holotypehas been examined in this study.   Remarks.I have examined the holotypeof  H. elsjeaeMakhan, including the male genitalia (ZMHB). Oliva (1996)synonymized  H. elsjeaeMakhanwith  H. obscurusSharp. However, this is undoubtedly incorrect as the male genitalia of the two markedly differ. Among the most obvious differences is that the male genitalia of  H. elsjeaehas large pseudoparameres, whereas  H. obscuruslacks pseudoparameres. Labels on the holotypeof  H. elsjeaeare: “Bo- livien 750m/ Prov. Sara II-06 / J. Steinbach S.V. // Zool. Mus. Berlin // Hydrochus elsjeae/ det. D. Makhan / 1994 // [red] Holotype// Hydrochus obscurus Sharp 1882det. A. Oliva 1996// HABITUS/GENIT. DIGITAL IMAGES captured 2019 P.D. Perkins”. [151,1335,1852,1879] Bolivia Originally 43 44 1 1 holotype