Contribution to the study of Epeorus Eaton, 1881 (Ephemeroptera: Heptageniidae) from India Author Vasanth, M. 0000-0003-4446-4889 Zoological Survey of India, Southern Regional Centre, Santhome High Road, Chennai- 600028, India. & University of Madras, Chepauk, Chennai- 600005. & vasan 071994 @ gmail. com; https: // orcid. org / 0000 - 0003 - 4446 - 4889 vasan071994@gmail.com Author Selvakumar, C. 0000-0002-4296-5682 Department of Zoology, The Madura College (Autonomous), Madurai- 625011, Tamil Nadu. & selvaaa 06 @ gmail. com; https: // orcid. org / 0000 - 0002 - 4296 - 5682 selvaaa06@gmail.com Author Subramanian, K. A. Zoological Survey of India, Southern Regional Centre, Santhome High Road, Chennai- 600028, India. Author Sivaramakrishnan, K. G. 0000-0002-6332-0349 Flat No 3, Door No 7, Gokulam Apartment, Gokulam Colony, West Mambalam, Chennai- 600 033, India. & kgskrishnan @ gmail. com; https: // orcid. org / 0000 - 0002 - 6332 - 0349 kgskrishnan@gmail.com Author Sinha, Bikramjit 0000-0002-9904-4964 Zoological Survey of India, Arunachal Pradesh Regional Centre, Senki Valley, Itanagar- 791113, Arunachal Pradesh, India. & sinhabj @ gmail. com; https: // orcid. org / 0000 - 0002 - 9904 - 4964 sinhabj@gmail.com text Zootaxa 2021 2021-06-25 4991 3 499 522 journal article 10.11646/zootaxa.4991.3.4 1175-5326 5042522 842EA450-A680-4D5D-9723-C1D7CCE13E5D Epeorus ( Caucasiron ) psi Eaton, 1885 ( Figs 102–116 ) Material examined: 12 larvae , INDIA , Arunachal Pradesh , West Kameng district , Dirang , Showda village , Dirang river , 27.32675 N , 92.23180 E , 1877 m , 13.iii.2018 , coll. Bikramjit Sinha [ZSI/ SRC-I /E-295] ; 18 larvae , Arunachal Pradesh , Lower Dibang valley district, Roing , Iphipani river , 28.18728 N , 95.84094 E , 488 m , 04.iv.2016 , coll. Santabala & Party [ZSI/ SRC / I/E-306-308] ; 4 larvae , Arunachal Pradesh , West Kameng district , Sangti valley , Khechalu , KhendoRong (stream), 27.420841 N , 92.269538 E , 1790 m , 12.iii.2018 , coll. Bikramjit Sinha [ZSI/ SRC-I /E-322] ; 2 larvae , India , Arunachal Pradesh , West Kameng district , Dirang , Chakpa village , Chakpar Rong (stream), 27.420265 N , 92.21811 E , 1749 m , 11.iii.2018 , coll. Bikramjit Sinha [ZSI/ SRC-I /E-328] . FIGURES 102–107. Larva of Epeorus ( Caucasiron ) psi 102 . Dorsal view; 103 . Ventral view; 104 . Labrum; 105 . Hypopharynx; 106 . Right mandible; 107 . Left mandible. FIGURES 108–116. Larva of Epeorus ( Caucasiron ) psi 108 . Maxilla; 109 . Labium; 110 . Foreleg; 111 . Midleg; 112 . Hindleg; 113 . Claw; 114 . Gill I; 115 . Gill V; 116 . Gill VII. Description: Mature larva: Body length 14 mm , cerci 16 mm . General colour brown ( Figs 101–102 ). Head: Body slightly convex dorsally. Frontal and lateral margins of head expanded, ( Fig. 102 ). Labrum rather small with hair-like setae dorsally and laterally; 2 times as wide as long, antero-lateral margins rather angulate; shallow excavation medially, anterior margin almost straight ( Fig. 104 ). Hypopharynx pale brown, lingua with anterolateral lobes; superlinguae slightly expanded ( Fig. 105 ). Mandible with scattered setae along molar area; incisor well developed; outer incisor longer than inner incisor ( Figs 106–107 ). Maxilla as in Fig. 108 . Labium: glossae with U-shaped separation; paraglossae slightly expanded laterally; apical segment of palp acutely pointed, dorsal surface with dense row of comb setae ( Fig. 109 ). Thorax: Pronotum brown; mesonotum dark brown anteriorly and a pair of lateroparapsidal sutures inside curved posteriorly ( Fig. 102 ). Legs: yellowish brown; femora with rounded medial hypodermal femur spot; joint of the femur and tibiae dark brown; outer margin of tibiae of all legs with dense row of long setae ( Figs 110–112 ). Claw with 2 denticles ( Fig. 113 ). Abdomen: Abdominal terga pale brown, abdominal terga with overturned letter Ψ on terga V–VIII; sterna II–VII with a pair of black slanting streaks and a brown line medially ( Fig. 103 ); segments I–IX medially with small hair-like setae along the mid-dorsal line. Posterolateral margins of segments I–VII with short and blunt extension ( Figs 102–103 ). Sterna pale brown with a pair of black slanting streaks and median black line ( Fig. 103 ). Gills: gill I very large, greatly extended beneath abdomen ( Figs 103 , 114 ); costal rib of gills II–VII with short thumb-like projection ( Figs 115–116 ); gill VII meets beneath body with short fibrilliform gills ( Fig. 116 ). Cerci dark brown. Adult: Description provided by Eaton (1885). Diagnosis: Epeorus ( Caucasiron ) psi can be identified by the following combination of characters: (i) femora with rounded medial hypodermal spot ( Figs 110–112 ); (ii) claw with 2 denticles ( Fig. 113 ); (iii) abdominal terga with overturned letter Ψ on terga V–VIII; sterna II–VII with a pair of black slanting streaks and a brown line medi- ally ( Fig. 103 ). Distribution: India ( Himachal Pradesh and Arunachal Pradesh ) Nepal and Taiwan . Remarks: The larval description of Epeorus (C.) psi from Nepal was provided for the first time by Braasch (1980) . Unfortunately, it is inaccurate and poorly illustrated with schematic drawings. An improved description is given herein which enables its inclusion is the subgenus Caucasiron as per the following diagnostic features provid- ed recently in Hrivniak et al . (2020a) . 1. Coloration of abdominal terga, including overturned letter Ψ on abdominal terga V–VIII ( Fig. 103 ). 2. Coloration of abdominal sterna, including slanting streaks on sterna II–VIII ( Fig. 103 ). 3. Medial hypodermal femoral spots ( Fig. 110–112 ). 4. Claw with 2 denticles ( Fig. 113 ). 5. Shape of gills II–VII ( Fig. 114–116 ) with an outer thumb-like projection.