Contribution to the knowledge of the subgenus Tenuibaetis Kang & Yang 1994 (Ephemeroptera, Baetidae, Baetis s. l.) Author Kluge, Nikita Department of Entomology, Saint Petersburg State University, Universitetskaya nab., 7 / 9, Saint Petersburg, 199034, Russia. Website: http: // insecta. bio. spbu. ru Author Srinivasan, Pandiarajan PG and Research department of Zoology, the American College, Madurai- 625002, India Author Sivaruban, T. 0000-0001-8997-9355 PG and Research department of Zoology, the American College, Madurai- 625002, India & sivaruban 270 @ gmail. com; https: // orcid. org / 0000 - 0001 - 8997 - 9355 sivaruban270@gmail.com Author Barathy, S. Department of Zoology, Fatima College, Madurai- 625018, India Author Isack, Rajasekaran 0000-0002-9952-4335 PG and Research department of Zoology, the American College, Madurai- 625002, India & iceisack 143 @ gmail. com; https: // orcid. org / 0000 - 0002 - 9952 - 4335 iceisack143@gmail.com text Zootaxa 2023 2023-05-02 5277 2 201 258 http://dx.doi.org/10.11646/zootaxa.5277.2.1 journal article 54348 10.11646/zootaxa.5277.2.1 83b6de69-6f04-4fa6-8c14-88d961694991 1175-5326 7889695 73ED69F3-3887-460D-86DE-C9F1302C8EC3 1. Baetis ( Tenuibaetis ) ursinus Kazlauskas 1963 ( Figs 22–43 ) Baetis ursinus Kazlauskas 1963: 585 (larva); Kluge 1983: 70 (♁ imago, larva); Kluge 1995: 17 ( type specimens). Baetiella ursina : Waltz & McCafferty 1987: 563 . Baetis ursinus ursinus : Novikova 1991 : figs 18–30 (larva). Baetis ( Baetis ) ursinus ursinus : Kluge 1997b: 194 (larva). Baetis ( Rhodobaetis ) ursinus : Jacob 2003: 120 . Baetis ( Tenuibaetis ) ursinus : Kluge 2022: 166 (subimago). Material examined ( ZIN ). Holotype : Irkutsk province , stream falling in river Angara 2 km upstream Zajarsk , 9. VII .1955 : parts of larva . Other material: RUSSIA : Khabarovskiy Kray : railway station Bira , 8. IX .1980 , coll. N. Kluge : L-S-I♁. Primorskiy Kray : river Ussuri near Bulyga-Fadeevka and Breevka , 1–12. VIII .1980 , coll. N. Kluge : L-S-I♁, 3 L-S♁, 3 L-S ♀ , 5 larvae ; Lazovskiy natural reserve, stream Sukhoy , 23. VIII .1980 , coll. N. Kluge : L-S/I♁. Ussuriyskiy natural reserve, river Komarovka , 22. VIII .1983 , coll. T . Vshivkova : 1 larva ; same locality, 27–28. VIII .1980 , coll. N. Kluge : L-S-I♁, L-S-I ♀ ; area of natural reserve «Kedrovaya Pad’» including river Narva , 13–26. VII .1980 , coll. N. Kluge : L-S-I♁, 2 L-S♁, 16 larvae ; river Barabashevka near Barabash , 15. VII .1976 , coll. N. Sinitshenkova & V . Zherikhin : 1 larva . MONGOLIA : river Orkhon WE Bulgan , 16–20. VIII .1997 , coll. N. Kluge : L-S-I♁, 8 larvae ; river Ider-Gol 40 km downstream Jargalt , 25. VIII .1997 , coll. N. Kluge : 1 larva ; basin of river Selenga , 19. VIII .1997 , coll. N. Kluge : L-S♁; river Orkhon near Kharkhorin , L-S♁, L-S-♁, 1 larva . Additional descriptions Larva . CUTICULAR COLORATION ( Figs 24–29 ): Described and figured by Novikova (1991 : figs 18–30); pronotum with lighter sigilla on darker background ( Fig. 28 ; Novikova 1991 : figs 18–19). HYPODERMAL COLORATION: Not expressed. SHAPE AND SETATION : Labrum of medium proportions ( Fig. 22 ; Kluge 1983 : fig. 41). Mandibles as in original description ( Kazlauskas 1963 : figs 21–22). Labial glossae, paraglossae and palp as in original description ( Fig. 23 ; Kazlauskas 1963 : fig. 23). Hind protoptera present (as in Fig. 2 ). Two-channel setae forming row along outer side of femur (including two subapical setae) elongate, blunt, distally widened and flattened ( Fig. 31 ; Kluge 1983 : fig. 43). Stout setae on anterior side of femur two-channel, from moderately long to short ( Fig. 31 ). FIGURES 22–30. Baetis ( Tenuibaetis ) ursinus , larval exuviae (24–29, one and the same magnification). 22, labrum; 23, maxilla and labium; 24, abdomen, 25–27, middle and hind legs; 28, half of pronotum and mesonotum; 29, head; 30, paraproct. FIGURES 31–32. Baetis ( Tenuibaetis ) ursinus , larval exuviae of fore leg. 31, part of femur; 32, part of tibia. Abbreviation: 2-can, two-channel setae. FIGURES 33–41. Baetis ( Tenuibaetis ) ursinus . 33, subimaginal exuviae of half of mesonotum; 34, hind wing of male; 35, hind wing of female; 36, male imago and its spread abdomen; 37–38, its fore and middle legs; 39–40, their subimaginal exuviae (the same magnification); 41, female imago. Tibia of each leg with small, stout two-channel setae on inner side and along patella-tibial suture; stout setae on outer side of tibia extremely small, with length subequal to cuticle thickness ( Fig. 32 ), more numerous on middle and hind tibiae, sparser or absent on fore tibiae. Denticles on posterior margins of terga I–X bluntly triangular ( Kluge 1983 : fig. 44; Novikova 1991: 17 ). Denticles on posterior margin of sternum small and irregular, present only on sternum IX , sometimes also on sterna VIII and VII ; in male, row of denticles not interrupted by protogonostyli; paraproct with denticles on most part of inner margin ( Fig. 30 ). Paracercus significantly smaller than cerci ( Fig. 24 ; Kazlauskas 1963 : fig. 20). Subimago . CUTICULAR COLORATION:Head colorless,antennae brown.Pronotum light brown.Mesonotum with ochre, light brownish and dark brown areas ( Fig. 33 ). Thoracic pleura and sterna with light brownish and dark brown areas (as in Fig. 215 ). Legs of all pairs with femur colorless, tibia and tarsus brownish ( Figs 39–40 ). Abdominal terga I– VIII light brownish, darker laterally; terga IX –X colorless (as in Fig. 172 ). Cerci light brown. HYPODERMAL COLORATION: As in imago. Imago, male ( Figs 34, 36–38 ). Described by Kluge (1983) . Middle and hind tarsi with 2 apical spines (on 1st+2nd and 3rd segments). Gonovectes bent under right angle, brown; sterno-styligeral muscle vestigial ( Figs 42–43 ). Imago, female ( Fig. 41 ). Head and thorax ochre with brown. Wings slightly tinged with brownish. Hind wing narrower than in male ( Fig. 35 ). All tarsi with 2 apical spines (fore tarsus on 2nd and 3rd segments, middle and hind tarsi on 1st+2nd and 3rd segments). Abdominal terga ochre medially, brownish laterally; sterna uniformly lighter ochre. Dimension. Forewing length 4–5 mm . Distribution. East Siberia, Mongolia and Russian Far East. Comments. Larva from Korea described and figured by Bae & Park (1998) under the name ́Baetis ursinus » does not belong to this species, since it has no V-shaped blank on mesonotum, has colorless fore protoptera and different coloration of abdominal terga; these authors referred to the publication by Kluge (1983) where male imago was described, but stated that ́Male adult. Unknown».