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 10.11646/zootaxa.5277.2.1 1175-5326 7889695 73ED69F3-3887-460D-86DE-C9F1302C8EC3 8. Baetis ( Tenuibaetis ) octomaculatus sp. n. ( Figs 15–19 , 242–278 ) Etymology. Allusion to eight contrasting dark brown maculae on abdominal terga in all stages of both sexes ( Figs 248 , 266, 267, 270, 271 ). Material examined. Holotype : L-S-I ♀ {specimen [XVIII](2) 2015}, THAILAND , Pai , river Moei , 14.II.2015 , coll. N. Kluge & L. Sheiko. Paratypes : the same place, date and collectors: 2 L-S-I ♀ , 1 S♁, 30 larvae ; river Pai , 11.I.1998 , coll. Grigorenko : 1 L/S ♁; Mae-Sae , 15–19. II .2015 , coll. N. Kluge & L. Sheiko : 2 larvae ; Erawan National Park , 2–4. II .2015 , coll. N. Kluge & L. Sheiko : 1 S-I♁, 1 S-I ♀ , 9 I♁, 2 larvae . Descriptions Larva . CUTICULAR COLORATION: Head brown ( Figs 243, 246 ). Pronotum brown, with sigilla slightly darker than background; mesonotum and fore protoptera brown, with diffusive blanks ( Fig. 242, 245 ). Thoracic pleura brownish, sterna colorless. Legs with darker and lighter brown areas; fore femur with wide oval proximal blank ( Figs 253–255 ). Abdominal terga vary from nearly uniformly brown to more or less contrasting; tergum IV either nearly as dark as others ( Fig. 247 ), or colorless laterally ( Fig. 244 ). Caudalii uniformly brown. HYPODERMAL COLORATION: In young and mature larvae of both sexes, abdominal terga II – III and VI – VII with pair of contrasting dark brown maculae; these and other abdominal terga with dark brown line on posterior margin ( Fig. 248 ). SHAPE AND SETATION : Labrum of medium proportions ( Fig. 249 ). Mandibles— Figs 250–251 . Maxilla and labium— Fig. 252 . Hind protoptera present ( Figs 17–19 ). Stout two-channel setae forming row along outer side of femur (including two subapical setae) elongate, blunt, distally widened and flattened ( Figs 253–255 ). Anterior-apical margin of femur with small, pseudo-bifurcate setae, as on tibiae ( Fig. 257 ). Stout setae on anterior side of femur mostly elongate, distally widened and rounded, varying from large to small ( Figs 253–255 , 257–258 ). Tibia of each leg with pseudo-bifurcate setae on outer side, smaller and sparser on fore leg ( Fig. 259 ), larger and denser on middle and hind legs ( Fig. 260 ). Stout setae along patella-tibial suture two-channel, short, distally widened and rounded ( Figs 259–260 ). Denticles on posterior margins of all abdominal terga I–X well-developed, short and blunt ( Figs 261–263 ). Denticles on posterior margin of sternum triangular, present on sternum IX ( Fig. 264 ), fewer on sternum VIII ; in male row of denticles not interrupted by protogonostyli. Paraproct with pointed denticles ( Fig. 264 ). Tergalius I much smaller than others ( Figs 244, 247 ). Paracercus significantly smaller than cerci ( Fig. 247 ). Subimago . CUTICULAR COLORATION: Head colorless, antennae brown. Pronotum with light brown and colorless areas. Mesonotum mostly light brownish ( Fig. 265 ). Thoracic pleura and sterna with light brownish and dark brown areas (as in Fig. 215 ). Legs brownish ( Fig. 274 ). Abdominal terga and sterna light brownish. HYPODERMAL COLORATION: In both sexes, abdominal terga mostly ochre; terga II – III and VI – VII with pair of contrasting dark brown maculae; these and other abdominal terga with dark brown line on posterior margin ( Fig. 271 ). Imago, male ( Figs 266, 272 ). Head light brown. Antennae light brown. Turbinate eyes with facetted surface orange, stem ochre. Thorax brown. Forewing with membrane entirely colorless; veins ochre or brown; pterostigma with few oblique cross veins and disconnected vein fragments. Hind wing diminished, colorless, with short and non-hooked costal projection, with 2 longitudinal veins ( Figs 15–16 ). Legs either uniformly ochre ( Fig. 273 ), or with diffusive reddish markings. Middle and hind tarsi with 2 apical spines (on 1st+2nd and 3rd segments). Abdominal terga II – III and VI – VII with pair of contrasting dark brown maculae and brownish-ochre area between them; these and other abdominal terga with dark brown line on posterior margin; terga IV – V mostly light ochre, tergum VIII mostly brownish-ochre, terga IX –X lighter ochre ( Figs 266, 272 . Cerci ochre. Gonostyli ochre; 1st segment slightly narrowing toward apex; 3rd (terminal) segment short, often truncate ( Fig. 277 ), sometimes clavate ( Fig. 276 ). Gonovectes sharply bent, light brownish. Sterno-styligeral muscle vestigial ( Fig. 277 ). Imago, female ( Figs 267, 270 ). Head ochre. Thorax ochre. Hind wing much smaller than in male ( Fig. 18 ). 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 mostly ochre; terga II – III and VI – VII with pair of contrasting dark brown maculae; these and other abdominal terga with dark brown line on posterior margin ( Figs 267, 270 ). FIGURES 242–248. Baetis ( Tenuibaetis ) octomaculatus sp. n . 242–247, exuviae of female larvae: 242, 245, half of pronotum and mesonotum; 243, 246, head; 244, 247, abdomen; 248, young larva to show hypodermal coloration (242–244, holotype). FIGURES 249–252. Baetis ( Tenuibaetis ) octomaculatus sp. n. 249, labrum (holotype); 250–251, left and right mandibles; 252, maxilla and labium. Dimension. Forewing length 4 mm . Distribution. Thailand . Comparison. The new species differs from other known species by peculiar hypodermal coloration which is well-expressed in all stages of the both sexes, i.e. with eight dark brown maculae, by a pair on the abdominal terga II, III, VI and VII. By greatly diminished hind wings of female, the new species resembles B . ( T .) parvipterus ; it differs from B . ( T .) parvipterus , besides the hypodermal coloration, by very long stout setae on anterior surface of femur.