Taxonomic revision of African water beetles in the genus Ochthebius Leach (1815) subgenus Aulacochthebius Kuwert (1887) (Coleoptera: Hydraenidae) Author Perkins, Philip D. text Zootaxa 2023 2023-01-17 5228 5 501 546 journal article 10.11646/zootaxa.5228.5.1 1175-5326 7543172 88FE61B0-65C6-4E22-8E18-B34BA534302C O. (Aulacochthebius) plicicollis Fairmaire Figs. 2 , 31 Ochthebius plicicollis Fairmaire 1898: 223 . Differential diagnosis. Similar in size (ca. 1.40 mm ) to O. (A.) tenuipunctus ; distinguished therefrom by the longer and deeper midlongitudinal impression of the pronotum, and by the aedeagus. Discussion. Both species of Malagasy O. ( Aulacochthebius ) , O. (A.) perlaevis (Perkins) and O. (A.) plicicollis Fairmaire , are typical species of the O. (A.) tenuipunctus Group, very smooth dorsally. The aedeagi of both species differ in the shape of the main-piece from that of other members of the group. O. (A.) plicicollis is known from only a few localities in Madagascar ( Fig. 29 ); whereas O. (A.) perlaevis is widely distributed on the island ( Fig. 32 ).