A new species of Ephoron Williamson, 1802 (Ephemeroptera: Polymitarcyidae) from Thailand Author Techakijvej, Chotiwut PhD Degree Program in Environmental Science, Environmental Science Research Center, Faculty of Science, Chiang Mai University, Author Sareein, Nattawut 0000-0003-4167-8902 Environmental Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand. & https: // orcid. org / 0000 - 0003 - 4167 - 8902 Author Hwang, Jeong Mi 0000-0003-4743-4474 Korean Entomological Institute, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Korea. & https: // orcid. org / 0000 - 0003 - 4743 - 4474 Author Bae, Yeon Jae 0000-0001-7810-5409 Korean Entomological Institute, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Korea. & Department of Environmental Science and Ecological Engineering, Graduate School, Korea University, Seoul 02841, Korea. https: // orcid. org / 0000 - 0001 - 7810 - 5409 Author Phalaraksh, Chitchol Environmental Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand. & Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand. text Zootaxa 2021 2021-06-15 4985 3 392 402 journal article 5696 10.11646/zootaxa.4985.3.6 ac091d94-86ff-45b9-9eb3-a00c8b173096 1175-5326 4956267 D0116147-5733-4276-9DC8-95FBE3762BD8 Genus Ephoron Williamson, 1802 Ephoron Williamson, 1802: 71 [ Type species: Ephoron leukon Williamson, 1802 ]. Polymitarcys Eaton, 1868: 84 [ Type species: Ephemera virgo Olivier, 1791 ]; synonymized by Spieth (1940) . Eopolymitarcys Tshemova, 1934: 240 [ Type species: Eopolymitarcys nigridorsum Tshemova, 1934 ]; synonymized by Edmunds and Traver (1954) . Diagnosis. The adults present wings whitish and hyaline, hindwings are well-developed with numerous cross veins and intercalaries. Forewings with a strong convex vein running parallel to CuP, attached to CuA. Hindwings have a blunt costal projection. In males, hindwings have a long intercalary vein between RA and RS (autapomorphy) ( Kluge 2004 ). Forelegs of males are developed, whereas mid- and hind legs are poorly developed. Male forceps with 4 segments, caudal filament is reduced. In females, all legs are poorly developed, one caudal filament and two cerci. The larvae of Ephoron have mandibles with long mandibular tusks covered with numerous tubercles. Tusks curve inwards near apex, easily visible from dorsal view. From lateral view, tusks curve downward. In some species ( E . shigae and E . limnobium ), tusks curve upwards at apex. Head has median frontal process. Forelegs have strong tubercles, specialized for burrowing. Midlegs are small and hindlegs are strong. Abdomen has gills on segments 1–7, gills 1 single and small, 2–7 forked with lateral margin fringed. Remarks. The larvae and adult characteristic of Ephoron are well described by Ishiwata (1996) , based on Japanese species, and Bauernfeind & Soldán (2013) for European fauna.