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 5. Baetis ( Tenuibaetis ) kaltenbachi sp. n. ( Figs 146–183 ) Etymology: This new species is named after Dr. Thomas Kaltenbach (UNIL, Department of Ecology and Evolution, Switzerland ) for his incredible contribution to the systematics and phylogeny of Baetidae . Material examined ( AMC ). Holotype : L-S-I♁, INDIA , Tamil Nadu state , Madurai , river Vaigai , 12.XII.2022 , coll. P. Srinivasan , R . Isack ( AMC ; new species register number 268) . Paratypes : the same locality, and collectors, 28–31.VII.2021 : 1 L-S-I♁, 1 L-S-I ♀ , 15 larvae ( AMC ; new species register number 269) . Larva. CUTICULAR COLORATION: Pronotum with brown and colorless areas, with sigilla lighter than background; mesonotum with brown and colorless areas; fore protoptera colored with yellowish ( Fig. 149 ). Thoracic pleura brownish, sterna colorless. Legs mostly colorless, tarsus with outer side brownish ( Figs 150–152 ). Abdominal terga with contrasting brown and colorless areas; terga IV – V mostly colorless, with pair of brown maculae submedially; terga IX –X mostly colorless ( Figs 146–148 ). Caudalii uniformly colorless. HYPODERMAL COLORATION: Abdominal terga with reddish or yellowish markings visible through colorless areas of cuticle ( Figs 146–147 ). SHAPE AND SETATION : Labrum of medium proportions ( Figs 154–155 ). Labium— Figs 156–158 . Hind protoptera present (as in Fig. 40 ). Stout two-channel setae forming row along outer side of femur (including two subapical setae) elongate, blunt, distally widened and flattened ( Fig. 165–166 ). Stout setae on anterior side of femur two-channel, varying from long to short ( Figs 165, 167 ). On each leg, stout setae on outer side of tibia pseudo-bifurcate; stout setae along patella-tibial suture partly pseudo-bifurcate, partly two-channel ( Figs 163–164 ). FIGURES 146–153. Baetis ( Tenuibaetis ) kaltenbachi sp. n .. 146–147, mature female and male larvae; 148–153, larval exuviae: 148, abdomen; 149, half of pronotum and mesonotum; 150–152, fore, middle and hind legs; 153, paraproct (148–153, holotype). Denticles on posterior margins of all terga I–X short and blunt ( Fig. 159 ). Denticles on posterior margin of sternum bluntly triangular.Tergalius I much smaller than others ( Fig. 148 ). Paracercus significantly smaller than cerci. Subimago . CUTICULAR COLORATION: Head colorless, antennae brown. Pronotum colorless. Mesonotum with ochre, light brownish and dark brown areas ( Fig. 177 ) Thoracic pleura and sterna with light brownish and dark brown areas (as in Fig. 215 ). Legs with femora lighter, tibiae and tarsi darker ( Figs 175–176 ). Abdominal terga I– VIII medially nearly colorless, laterally diffusively darkened; terga IX –X entirely light ( Fig. 172 ). FIGURES 154–159. Baetis ( Tenuibaetis ) kaltenbachi sp. n . , larval exuviae (holotype). 154–155, labrum; 156–158, labium; 159, posterior margin of abdominal tergum I. FIGURES 160–168. Baetis ( Tenuibaetis ) kaltenbachi sp. n . , larval exuviae (holotype). 160–162, femora of fore, middle and hind legs; 163–164, tibiae of fore and middle legs; 165, fragment of fore femur; 166–167, fragments of mid femur; 168, claw. FIGURES 169–180. Baetis ( Tenuibaetis ) kaltenbachi sp. n . 169–170, male imago; 171, female imago; 172, subimaginal exuviae of abdomen; 173–174, fore and middle legs of male imago; 175–176, their subimaginal exuviae; 177, subimaginal exuviae of half of mesonotum; 178, hind wing of male imago; 179, the same, female; 180, blunt microlepides on fore tarsus of male subimago (169–170, 172–178, 180, holotype). HYPODERMAL COLORATION: As in imago. Imago, male ( Figs 169–170 ). Head ochre. Antennae ochre. Turbinate eyes with facetted surface red, stem ochre with orange. Pronotum ochre with reddish maculae, prosternum whitish with reddish. Mesonotum mostly ochre, mesopleura ochre with reddish markings, mesosternum whitish with furcasternal protuberances gray-brown. Forewing with membrane colorless, veins ochre; pterostigma with few oblique cross veins and disconnected vein fragments. Hind wing full-sized, colorless, with short and non-hooked costal projection, with 2 longitudinal veins ( Fig. 178 ). Legs ochre with diffusive light reddish marking on distal part of femur ( Figs 169, 173–174 ). Middle and hind tarsi with 2 apical spines (on 1st+2nd and 3rd segments).Abdominal terga I– IV and IX –X mostly whitish, terga V – VIII mostly brown; terga II – III and V – VIII with reddish-brown maculae laterally; all terga I–X with reddish or brown band bordering posterior margin and not reaching lateral margins ( Fig. 169 ). Abdominal sterna mostly whitish, with gray-brown lateral areas, most extensive on sternum VIII and least extensive on sternum IV ( Fig. 170 ). Cerci ochre. Gonostyli ochre; 1st segment relatively narrow, nearly parallel-sided; 3rd (terminal) segment short and truncate ( Figs 181–183 ). Imago, female ( Fig. 171 ). Coloration of head and thorax similar to that of male. Abdominal terga ochre, with reddish-brown lateral maculae and band bordering posterior margin. Hind wing narrower than in male ( Fig. 179 ). All tarsi with 2 apical spines (fore tarsus on 2nd and 3rd segments, middle and hind tarsi on 1st+2nd and 3rd segments). FIGURES 181–183. Baetis ( Tenuibaetis ) kaltenbachi sp. n . , genitalia of male imago (holotype). Dimension. Forewing length 4 mm . Distribution. Southern India . Comparison. The new species differs from other species by peculiar hypodermal coloration of male imaginal abdomen, which is sharply different on terga II–III, IV, V–VIII and IX–X ( Fig. 169 ).