taxonID	type	description	language	source
C700DE52FFABFFE1FF55FE86FEB9FCEB.taxon	vernacular_names	[Japanese name " Erumon-hirata-kagerou "]	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFABFFE1FF55FE86FEB9FCEB.taxon	materials_examined	Materials examined. Type specimens: We investigated the Aquatic Insects Collection at The Kyoto University Museum in 2019 but were unable to find the holotype of E. latifolium. Ishiwata (2018) also noted that the types and other materials collected by Uéno were missing. Syntypes of Iron uenoi Matsumura, 1933 (identification label by Imanishi, 1933, " Iron uenoi Imanishi, Det. K. Imanishi 1933 ". All dried specimens.): 3 male imagines, " Maruyama [in Kanji 円山], 5 / 27 " (collection years not listed), one with other labels (Fig. 32): " Type Matsumura " (red label) and " Epeorus uenoi Matsumura. Det. by S. Ishiwata, 1992 " (identification label by Shin-ichi Ishiwata, 1992); 2 male imagines, " Sahoro [in Katakana サホロ, probably meaning Sapporo], 5 / 27 " (collection years not listed); 1 male imago, " Sahoro [in Katakana サホロ, meaning Sapporo], 5 / 26 " (collection years not listed); 1 male imago, " Sapporo, Matsumura; 2 / VI ' 08 " (with collection date June 2 nd, 1908); 1 male imago, " Maruyama [in Kanji 円山], 6 / 7 " (collection years not listed). Other specimens: JAPAN, HOKKAIDO, ISHIKARI: [1.] Sapporo-shi, Minami-ku, Jozankei, Toyohira-gawa Riv., mainstream, 678 m a. s. l. (42 ° 47 ' 57.0 " N, 141 ° 10 ' 14.3 " E), 5 mature male nymphs and 1 mature female nymph, 15. VIII. 2003, K. Saito; ditto, 1 mature female nymph, 18. X. 2003, K. Saito; [2.] Sapporo-shi, Minami-ku, Jozankei, Izarisawa-gawa Stream (a tributary of Toyohira-gawa Riv.), 568 m a. s. l. (42 ° 51 ' 18.4 " N, 141 ° 10 ' 34.0 " E), 2 mature male nymphs and 1 mature female nymph, 14. VI. 2007, K. Saito; ditto, 3 mature male nymphs and 5 mature female nymphs, 11. IX. 2007, K. Saito; [3.] Sapporo-shi, Minami-ku, Jozankei, Toyohira-gawa Riv., upstream of confluence of mainstream and Ekiteisawa-gawa Stream, 514 m a. s. l. (42 ° 51 ' 18.1 " N, 141 ° 08 ' 59.0 " E), 1 mature male nymph and 1 mature female nymph, 12. VI. 2003, K. Saito; [4.] Sapporo-shi, Minami-ku, Jozankei, Usubetsu-gawa Stream (a tributary of Toyohira-gawa Riv.), 472 m a. s. l. (42 ° 54 ' 33.5 " N, 141 ° 07 ' 28.9 " E), 1 mature female nymph, 11. V. 2002, K. Saito; ditto, 1 mature female nymph, 08. IX. 2002, K. Saito; ditto, 1 mature male nymph, 06. VII. 2003, K. Saito; [5.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), the confluence of Shirai-gawa Stream and Migimata-gawa Stream, 450 m a. s. l. (42 ° 59 ' 39.6 " N, 141 ° 04 ' 42.9 " E), 3 mature male nymphs and 3 mature female nymphs, 6. VI. 2004, K. Saito; [6.] Sapporo-shi, Minami-ku, Jozankei, Otarunai-gawa Stream (a tributary of Toyohira-gawa Riv.), 502 m a. s. l. (43 ° 04 ' 22.4 " N, 141 ° 06 ' 34.8 " E), four mature male nymphs and 2 mature female nymphs, 11. V. 2002, K. Saito; ditto, 4 mature male nymphs and 6 mature female nymphs, 6. VII. 2002, K. Saito; ditto, 1 mature male nymph and 2 mature female nymphs, 7. iv. 2019, T. Takayanagi; ditto, 3 mature female nymphs, 21. IX. 2019, T. Takayanagi; [7.] Sapporo-shi, Minami-ku, Jozankei, Otarunai-gawa Stream (a tributary of Toyohira-gawa Riv.), 394 m a. s. l. (43 ° 01 ' 56.1 " N, 141 ° 07 ' 42.9 " E), 1 mature male nymph, 18. VI. 2007, K. Saito; [8.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), 300 m a. s. l. (42 ° 58 ' 37.7 " N, 141 ° 08 ' 16.4 " E), 1 mature male nymph, 14. VI. 2005, K. Saito; ditto, 1 mature female nymph, 13. VIII. 2005, K. Saito; ditto, 1 mature male nymph, 07. IV. 2019, T. Takayanagi; [9.] Sapporo-shi, Minami-ku, Jozankei, Usubetsu-gawa Stream (a tributary of Toyohira-gawa Riv.), 353 m a. s. l. (42 ° 56 ' 29.4 " N, 141 ° 07 ' 47.3 " E), 2 mature male nymphs, 07. IV. 2019, T. Takayanagi; [10.] Sapporo-shi, Minami-ku, Toyama, Kannonzawa-gawa Stream (a tributary of Toyohira-gawa Riv.), 267 m a. s. l. (42 ° 58 ' 31.0 " N, 141 ° 15 ' 30.0 " E), 2 male imagines, 2 female imagines, 1 mature female nymph and 1 immature nymph, 29. V. 2018, T. Takayanagi; ditto, 1 mature male nymph and 1 immature nymph, 04. XI. 2018, T. Takayanagi; ditto, 1 mature female nymph, 19. III. 2019, T. Takayanagi; ditto, 5 male imagines and 4 female imagines, 23. V. 2019, T. Takayanagi; ditto, 1 mature female nymph, 16. XII. 2019, T. Takayanagi; ditto, 1 mature male nymph, 10. V. 2020, T. Takayanagi; ditto, 5 male imagines, 29. V. 2020, T. Takayanagi; [11.] Sapporo-shi, Minami-ku, Toyotaki, Toyohira-gawa Riv., mainstream, 188 m a. s. l. (42 ° 57 ' 38.4 " N, 141 ° 13 ' 50.9 " E), 2 mature male nymphs, 21. V. 2020, T. Takayanagi; [12.] Sapporo-shi, Minami-ku, Makomanai, Toyohira-gawa Riv., mainstream, 82 m a. s. l. (42 ° 59 ' 02.5 " N, 141 ° 20 ' 23.5 " E), 4 mature female nymphs, 12. IV. 2019, T. Takayanagi; [18.] Sapporo-shi, Nishi-ku, Heiwa, Kotonihassamu-gawa Stream (a tributary of Shin-kawa Riv.), 312 m a. s. l. (43 ° 03 ' 25.3 " N, 141 ° 12 ' 40.6 " E), 1 mature male nymph, 03. V. 2020, T. Takayanagi; [19.] Chitose-shi, Shikotsuko-onsen, Shirisetsunai-gawa Stream (an inlet stream of Lake Shikotsu-ko), 289 m a. s. l. (42 ° 46 ' 39.0 " N, 141 ° 24 ' 05.8 " E), 1 mature male nymph, 2 mature female nymphs and 1 immature nymph, 23. V. 2019, T. Takayanagi; ditto, 7 mature female nymphs, 21. IX. 2019, T. Takayanagi; ditto, 2 mature male nymphs and 3 mature female nymphs, 09. IX. 2020, T. Takayanagi; ditto, 2 mature male nymphs and 2 mature female nymphs, 01. VI. 2021, T. Takayanagi; ditto, 1 mature male nymph and 1 mature female nymph, 15. VIII. 2021, T. Takayanagi; [20.] Chitose-shi, Bifue, Bifue-gawa Stream (an inlet stream of Lake Shikotsu-ko), 257 m a. s. l. (42 ° 43 ' 47.9 " N, 141 ° 15 ' 18.2 " E), 2 mature male nymphs, 07. IV. 2019, T. Takayanagi; ditto, 1 mature female nymph, 23. V. 2019, T. Takayanagi; [23.] Eniwa-shi, Banjiri, Rarumanai-gawa Stream (a tributary of Chitose-gawa Riv.), 305 m a. s. l. (42 ° 51 ' 56.1 " N, 141 ° 20 ' 31.5 " E), 1 mature male nymph, 07. IV. 2019, T. Takayanagi. Nymph (mature, in ethanol), redescription (Figs 5 – 7, based on specimens collected from type locality [19.]). Body length 10.0 – 14.5 mm (male), 10.0 – 15.5 mm (female). Cercus length ca. body length x 1.2. Head. Shape ellipsoid. Color yellowish-brown to reddish-brown with pale markings. Compound eyes dark gray to black. Ocelli dark gray. Antennae brown. Anterior margin densely covered with hair-like setae extending to lateral margins. Dorsal surface of head covered with fine hair-like setae. Sparse longer fine hair-like setae located posteriorly to the eyes (Figs 6 a, b). Labrum: anterior and lateral margins evenly convex, anterior margin concave medially. Ventral surface with long antero-lateral bristles, row of short setae and brush of median fine hair-like setae on each side. Dorsal surface medially with four long adjacent bristles and two long bristles near each side of antero-lateral margin, and scattered variable-length setae (Fig. 7 a). Mandibles: each outer incisor with three apical teeth and serrated margins, inner incisor with two apical teeth (right mandible) or four apical teeth (left mandible) and both inner incisors sharply serrated, right inner incisor slender and almost straight. Tuft of long setae on the base of inner incisor of right mandible, tuft of long setae and one brachy-pulmose seta on the base of inner incisor of left mandible (Figs 7 b, c). Maxillae: one long, feather-like seta at base of apical tooth complex, some specimens with two setae on right maxilla (Fig. 28 a). Hypopharynx: superlinguae distally widened, lingua shape subquadrate. Labium: labial palps two segmented, outer margin of proximal segment with sparse, thick setae. Distal segment with sparse, hair-like setae on outer margin and dense, brush-like setae on distal 1 / 3 area. Glossae and paraglossae with long, dense setae.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFABFFE1FF55FE86FEB9FCEB.taxon	description	Thorax. Yellowish-brown to reddish-brown with pale markings dorsally (Figs 5 a, d). Ventrally white (Figs 5 b, e). Pronotum roundly projecting laterally (Fig. 29 a). Long hair-like setae on medial line to posterior margin of pronotum. Long hair-like setae on medial line to posterior area of mesonotum. Legs. Each anterior face of femur with dark brown transverse markings on its proximal, medial, and distal parts and hypodermal black spots on its base and middle (Fig. 6 c). Dorsal edge of femur with dense long blade-like setae, ventral edge with sparse short bluntly pointed spines. Femoral surface with diversely shaped setae: oblong, spatulate or semi-circular, those near ventral edge tend to be oblong, and those near dorsal edge tend to be semi-circular (Fig. 7 d). Tibia with two dark-brown markings on base and middle parts and long hair-like setae on dorsal edge (Fig. 6 c). Tarsus darker in proximal area and dorsal edge with long hair-like setae (Fig. 6 c). Tarsal claw with 4 – 5 small denticles. Abdomen. Terga yellowish-brown to reddish-brown, each tergum III – IX with a pair of dark spots. Tergum VII tends to be darker (Figs 5 a, d). Sterna white to slightly brown (Figs 5 b, e). Each surface of tergum with a cluster of long setae located to each side of midline. Posterior margin of each tergum with long setae and denticles which are uniform, sturdy and arranged in an even line (Figs 7 k, 31 a). Tergum I – VII each with three postero-lateral projections, ventral one blunt, lateral one pointed and bending slightly upward, and dorsal one blunt (Fig. 30 a). Posterior margin of sternum IX shape round with shallow medial emargination and covered with hair-like setae medially to laterally (Figs 7 i, j). Dorsal surface of cercus with a row of fine setae. Gills. Gills III and IV largest in size, VII smallest. Each gill with variably sized dark-violet spots on its posterior half, ground color slightly purple (Fig. 6 d). Gills II – VII with dark colored anal-proximal projections (Figs 6 d, 7 f, g). Costal margin of gill I with fine hair-like setae. Costal margin of gills II – VII with rough surface of spines and distal margin with fine setae. Each gill plate with filaments forming a fan-shape together. Gill VII without longitudinal fold (Fig. 7 h). Male imago (in ethanol), redescription (Fig. 8). Body length 11.0 – 13.4 mm. Cercus length ca. body length x 3.0. Forewing length 12.6 – 14.3 mm. Head. Yellowish-brown. Frons shape triangular. Compound eyes dark-gray to black, gray to greenish-gray when alive. Ocelli light-gray with black border (Fig. 8 g). Thorax. Ground color yellowish-brown to translucent, musculature visible. Each side of pronotum dark. Mesonotum with dark-brown markings on adjacent parts of sutures and scutellum (Fig. 8 g). Mesopleuron with dark-brown to black speckles. Metathorax color dark-brown with black speckles (Fig. 8 a). Wings. Hyaline, veins and axillary cord brown. Forewing with black markings on costal brace (Fig. 8 e). Pterostigmatic area cloudy. Hindwing without markings. Legs. Whitish brown. Anterior face of each femur with dark linearly shaped spot and elliptic spot. Fore tarsus longest with each segment becoming shorter distally (Figs 8 b – d). Tarsal claws dissimilar, one hooked-shape and the other oblong. Abdomen. Yellowish-brown, translucent with each posterior margin of tergum dark-brownish. Segments VIII – X yellowish white, internal organs and tissues visible (Fig. 8 a). Posterior margin of styliger plate roundly extended, forceps base with developed projection which has spines on its surface. Forceps four segmented, color dark-brown, with short comb-like spines on inner surface, fourth segment with sharp setae on its surface. Apical part of each penis lobe with proximally-oriented spine, titillators absent (Fig. 8 f). Cercus brown. Female imago (in ethanol) (Fig. 9). Body length 11.1 – 11.6 mm. Cercus length ca. body length x 2.2. Forewing length 13.2 – 15.0 mm. Head. Yellowish-brown. Compound eyes gray to dark gray. Ocelli as in male imago. Thorax. Coloration as in male imago (Fig. 9 a). Wings. Vein coloration as in male imago. Forewing slightly more expanded than in male (Fig. 9 a). Legs. Coloration and markings as in male imago. Fore tarsus not elongated. Of all tarsal segments, fourth is shortest, other segments almost equal in length (Figs 9 b – d). Tarsal claws dissimilar as in male imago. Abdomen. Yellowish-brown, greenish eggs visible when alive. Posterior margin of subgenital plate almost straight. Posterior margin of sternum IX rounded with shallow emargination (Fig. 9 e). Cercus brown.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFABFFE1FF55FE86FEB9FCEB.taxon	diagnosis	Diagnosis and comparison. Nymph. The nymphs of this species and the following species have variably sized dark-violet spots on their gills, in contrast to the other three species in the study area. See counterparts of the next species for a detailed comparison. Male imago. This species lacks penial titillators in contrast to all other species in the study area.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFABFFE1FF55FE86FEB9FCEB.taxon	discussion	Remarks. Nymph. The specimens here identified as E. latifolium agree with the original description (Uéno 1928). Body coloration may vary depending on the environment: specimens from more open and brighter parts of the river tend to have paler coloration, while those from darker, shaded areas exhibit darker coloration. Consequently, descriptions of coloration may vary according to each author's observations. Male imago. Almost all features correspond to the description by Uéno (1931 b), though the color of cerci is notably different. In Uéno (1931 b), its color was described as " white ". Although we can't explain this difference, we identify this species as E. latifolium based on the genetic collation of the nymph and morphological correspondence as a whole. Female imago. This is the first description of the female imago. Subgenus attribution. This species is the type species of the subgenus Belovius. The species concept of this species has been ambiguous since its original description. It was first described as a new species based on nymphal specimens collected in the Shirisetsunai-gawa Stream, Chitose, Hokkaido (locality [19.] in this study), in September (Uéno 1928). The following year, Horasawa (1929) reported nymphal, male-subimaginal, and male-imaginal stages based on materials collected from central Honshu at the beginning of September. However, this report was based on a misidentification (Ishiwata 2018). Uéno (1931 b) described the male imago based on materials from central Honshu, listing Horasawa’s work (1929) in the synonymy. However, critical discrepancies existed in the imaginal morphology descriptions, including differences in forewing markings and penis shape. Unfortunately, the materials examined in these studies are likely lost (Ishiwata 2018; Author’s investigation 2019). Further confusion about species delineation among “ latifolium - like ” species was first noted by Imanishi (1940), and these issues remain unresolved (discussed below). This study investigated genetic and morphological features of nymphal specimens from the type locality and strongly suggests that only one “ latifolium - like ” species exists in this area, thus confirming the species concept of E. latifolium as described above. Epeorus uenoi was described by Matsumura in Illustrated Common Insects of Japan under the name " Iron uenoi Imanishi " (Matsumura 1933), but authorship should be attributed to Matsumura (Ishiwata 2001 a). We concluded that this species is a junior subjective synonym of E. latifolium for the following reasons: 1) the genital structures of the E. uenoi syntypes match our observations of E. latifolium, displaying no titillators, a triangular styliger plate, and proximally oriented spines on the top of each penis lobe (Fig. 32 d); 2) all syntypes were collected in late May to early June, aligning with the first emergence period of E. latifolium identified in this study. Emergence periods and habitat. Fully mature nymphs and imagines were collected from early May through October. Mature nymphs collected in spring are larger (13 mm to 15 mm) and become smaller in later seasons. This species was observed upstream in the Makomanai district (locality [12.]) of the Toyohira-gawa River.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFABFFE1FF55FE86FEB9FCEB.taxon	distribution	Distribution. Japan (Hokkaido, Honshu, Shikoku, and Kyushu), Korea, China (Northeast), and Russia (Altai, Far East).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFADFFF8FF55FBB3FC20FA0A.taxon	vernacular_names	[Japanese name " Matsumura-hirata-kagerou "]	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFADFFF8FF55FBB3FC20FA0A.taxon	materials_examined	Materials examined. Type specimens: Syntypes: (an identification label by Imanishi, 1933, " Epeorus latifolium Uéno, Syn. Epeorus L-nigrum Matsumura, Det. K. Imanishi 1933 "). 1 male imago, " 9 / VIII 1903, Ishiyama "; 1 male imago, " Sapporo, Matsumura; 6 / VII 1915 ", " Epeorus L-nigrum M. det. Matsumura "; 1 male imago and 1 female imago, " Sapporo, Matsumura; 28 / VII 1915 "; 1 male imago (Fig. 33), " Sapporo, Matsumura; 28 / IX 1921 ", " Type Matsumura; Epeorus l-nigrum M " (red label); 1 male imago, " Sapporo, Matsumura; ĭDz (means " garden light "), 10 / IX. 1931 "; 2 male imagines, " Maruyama [in Kanji], 6 / 7 (year not listed) "; 1 male imago, " Sapporo, Matsumura; 25 / VI ?? 8 (year unreadable) "; 1 male imago, " Sapproro, Matsumura; 21 / ?? 20 (unreadable) "; 1 female imago, " Sapporo, Matsumura " (collection date not listed). Other specimens: JAPAN, HOKKAIDO, ISHIKARI: [3.] Sapporo-shi, Minami-ku, Jozankei, Toyohira-gawa Riv., upstream of confluence of mainstream and Ekiteisawa-gawa stream, 514 m a. s. l. (42 ° 51 ' 18.1 " N, 141 ° 08 ' 59.0 " E), 1 mature female nymph, 18. X. 2003, K. Saito; [4.] Sapporo-shi, Minami-ku, Jozankei, Usubetsu-gawa Stream (a tributary of Toyohira-gawa Riv.), 472 m a. s. l. (42 ° 54 ' 33.5 " N, 141 ° 07 ' 28.9 " E), 1 mature female nymph, 08. IX. 2002, K. Saito; [7.] Sapporo-shi, Minami-ku, Jozankei, Otarunai-gawa Stream (a tributary of Toyohira-gawa Riv.), 394 m a. s. l. (43 ° 01 ' 56.1 " N, 141 ° 07 ' 42.9 " E), 3 mature male nymphs and 1 mature female nymph, 11. IX. 2007, K. Saito; [11.] Sapporo-shi, Minami-ku, Toyotaki, Toyohira-gawa Riv., mainstream, 188 m a. s. l. (42 ° 57 ' 38.4 " N, 141 ° 13 ' 50.9 " E), 1 mature male nymph, 14. VI. 2005, K. Saito; ditto, 1 mature male nymph, 13. VIII. 2005, K. Saito; ditto, 3 male imagines, 15. VI. 2020, T. Takayanagi; [12.] Sapporo-shi, Minami-ku, Makomanai, Toyohira-gawa Riv., mainstream, 82 m a. s. l. (42 ° 59 ' 02.5 " N, 141 ° 20 ' 23.5 " E), 1 mature female nymph, 12. IV. 2019, T. Takayanagi: [13.] Sapporo-shi, Minami-ku, Makomanai, Toyohira-gawa Riv., mainstream, 68 m a. s. l. (42 ° 59 ' 58.5 " N, 141 ° 20 ' 26.0 " E), 5 mature male nymphs and 6 mature female nymphs, 26. VI. 2006, K. Saito; ditto, 2 mature male nymphs and 3 mature female nymphs, 02. IX. 2006, K. Saito; [14.] Sapporo-shi, Minami-ku, Minami 30 - jo, Nishi 8 - chome, Yamahana-gawa Stream (a tributary of Toyohira-gawa Riv.), 51 m a. s. l. (43 ° 01 ' 09.3 " N, 141 ° 20 ' 56.1 " E), 1 male imago, 23. VI. 2018, F. Matsui; [15.] Sapporo-shi, Chuo-ku, Minami 13 - jo, Nishi 1 - chome, Toyohira-gawa Riv., mainstream, 28 m a. s. l. (43 ° 02 ' 35.3 " N, 141 ° 21 ' 31.7 " E), 4 mature male nymphs and 1 mature female nymph, 16. V. 2020, T. Takayanagi; ditto, 1 mature male nymph and 1 mature female nymph, 19. viii. 2020, T. Takayanagi; ditto, 6 mature male nymphs and 1 mature female nymph, 25. IX. 2020, T. Takayanagi; ditto, 1 mature female nymph, 24. VII. 2021, T. Takayanagi; ditto, 2 mature female nymphs, 08. VIII. 2021, T. Takayanagi; [16.] Sapporo-shi, Chuo-ku, Kita 1 - jo, Higashi 19 - chome, Toyohira-gawa Riv., mainstream, 15 m a. s. l. (43 ° 04 ' 04.8 " N, 141 ° 23 ' 13.2 " E), 11 mature male nymphs and 15 mature female nymphs, 26. VI. 2006, K. Saito; ditto, 3 mature male nymphs and 9 mature female nymphs, 02. IX. 2006, K. Saito; ditto, 1 mature male nymph, 25. X. 2006, K. Saito; ditto, 1 male imago, 26. VII. 2018, T. Takayanagi; ditto, 2 male imagines, 1 mature male nymph and 2 mature female nymphs, 21. VIII. 2021, T. Takayanagi; [17.] Sapporo-shi, Kita-ku, Kita 11 - jo, Nishi 1 - chome, Sosei-gawa Riv. (a tributary of Fushiko-gawa Riv.), 15 m a. s. l. (43 ° 04 ' 30.9 " N, 141 ° 21 ' 10.9 " E), 2 male imagines and 1 female imago, 23. VI. 2021, T. Takayanagi; ditto, 1 female imago, 02. VII. 2021, T. Takayanagi; ditto, 1 female imago, 12. VII. 2021; [21.] Chitose-shi, Rankoshi, Chitose-gawa Riv., mainstream, 31 m a. s. l. (42 ° 48 ' 34.1 " N, 141 ° 34 ' 28.6 " E), 1 male imago, 06. VII. 2020, T. Ito; [22.] Chitose-shi, Shincho, Chitose-gawa Riv., mainstream, 13 m a. s. l. (42 ° 49 ' 07.7 " N, 141 ° 38 ' 25.8 " E), 1 male imago and 3 female imagines, 05. IX. 2017, N. Kuhara; HIYAMA (outside of the study area): Assabu-cho, Shirooka, Sasamodosawa-gawa Riv., 76 m a. s. l. (41 ° 49 ' 59.0 " N, 140 ° 19 ' 57.6 " E), 1 male imago, 08. VII. 2019, T. Takayanagi. Nymph (mature, in ethanol) (Figs 10 – 12). Body length 9.8 – 11.0 mm (male), 9.4 – 9.8 mm (female). Cercus length ca. body length x 1.2. Head. Shape ellipsoid. Color yellowish-brown to reddish-brown with pale markings. Compound eyes dark-gray to black. Ocelli dark-gray. Antennae brown. Anterior margin densely covered with hair-like setae extending to lateral margins. Dorsal surface of head covered with fine hair-like setae. Sparse longer fine hair-like setae located posterior to eyes (Figs 11 a, b). Labrum: anterior and lateral margins evenly convex, anterior margin concave medially. Ventral surface with long antero-lateral bristles, row of short setae and brush of median fine hair-like setae on each side. Dorsal surface with four long bristles medially and two long bristles near each side of antero-lateral margin, and scattered variable-length setae (Fig. 12 a). Mandibles: each outer incisor with three apical teeth and serrated margins, inner incisor with two apical teeth (right mandible) or four apical teeth (left mandible) and outer margin of right inner incisor serrated sharply, right inner incisor slender and almost straight. Tuft of long setae at base of inner incisor of right mandible, tuft of long setae and one brachy-pulmose seta on the base of inner incisor of left mandible (Figs 12 b, c). Maxillae: one long, feather-like seta at base of apical tooth complex, some specimens with two setae (Fig. 28 b). Hypopharynx: superlinguae distally widened, lingua shape subquadrate. Labium: labial palps two segmented, outer margin of proximal one with sparse, thick setae. Distal segment with sparse, hair-like setae on outer margin and dense, brush-like setae on distal 1 / 3 area. Glossae and paraglossae with long, dense setae.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFADFFF8FF55FBB3FC20FA0A.taxon	description	Thorax. Color yellowish-brown to reddish-brown with pale markings dorsally, white ventrally (Fig 10). Pronotum roundly projecting laterally (Fig. 29 a). Long hair-like setae on medial line to posterior margin of pronotum. Long hair-like setae on medial line to posterior area of mesonotum. Legs. Each anterior face of femur with dark-brown transverse markings on its proximal, medial, and distal parts and hypodermal black spots on its base and middle (Fig. 11 c). Dorsal edge of femur with dense long blade-like setae, ventral edge with sparse short bluntly pointed spines. Femoral surface with diversely shaped setae: oblong, spatulate or semi-circular. Those near ventral edge of each femur tend to be oblong, and those near dorsal edge of each femur tend to be semi-circular. Tibia with two dark-brown markings on base and middle parts and long hair-like setae on dorsal edge. Tarsus darker in proximal area and dorsal edge with long hair-like setae (Fig. 11 c). Tarsal claw with 4 – 5 small denticles. Abdomen. Terga yellowish-brown to reddish-brown, each tergum III – IX with a pair of dark spots. Sterna white. Surface of each tergum with a cluster of long setae located to each side of midline. Posterior margin of each tergum with long setae and long, sharp denticles which are uniform and arranged in an even line (Figs 12 g, 31 b). Tergum I – VII each with three postero-lateral projections, ventral one blunt, lateral one long, pointed and bending slightly upward and dorsal one blunt (Fig. 30 b). Posterior margin of Sternum IX with deep medial emargination forming sharp tips and covered in hair-like setae (Figs 12 d, e). Dorsal surface of cercus with a row of fine setae. Gills. Gills III and IV largest in size, VII smallest. Each gill with variably sized, dark-violet spots on its posterior half, ground color slightly purple (Fig. 11 d). Gills II – VII with anal-proximal projections, dark colored (Fig. 11 d). Costal margin of gill I with fine hair-like setae. II – VII costal margin with rough surface of spines and distal margin with fine setae. Each gill plate with filaments forming a fan-shape together. Gill VII without longitudinal fold. Male (in ethanol), redescription (Fig. 13). Body length 9.6 – 12.9 mm. Cercus length ca. body length x 2.8. Forewing length 9.3 – 13.3 mm. Head. Color white. Frons shape triangular. Compound eyes dark-gray to black, light-blueish-gray when alive. Ocelli grayish-white with dark-gray border (Fig. 13 g). Thorax. Ground color brownish-white to translucent, internal tissues visible. Pronotum with a pair of black line. Mesonotum with thick black markings on adjacent parts of sutures (Fig. 13 g). Meso- and metapleuron with black markings (Fig. 13 a). Wings. Hyaline, veins white to translucent. Pterostigmatic area cloudy. Forewing with black markings on the base of radius and cubitus to costal brace, junction of costal brace and costa and base of costa (Fig. 13 e). Forewing axillary cord color black. Hindwing with black spot on the base of cubitus to the base of radius. Legs. Anterior face of fore femur with black line on its proximal half. Fore tibia with dark spot on its distal tip. Fore tarsus longest with each segment becoming shorter distally and each joint dark. Mid and hind femur with discontinuous black lines. Fourth segment of mid and hind tarsus shortest (Figs 13 b – d). Tarsal claws dissimilar, one hooked-shape and the other oblong. Abdomen. Ground color white to translucent. Posterior margin of each tergum color dark. Segments VIII – X color white, internal organs and tissues visible (Fig. 13 a). Posterior margin of styliger plate shape edged and triangular, forceps base with developed projection which has sharp spines. Forceps four-segmented, with short comb-like spines on each inner surface, distal two segments dark in color, fourth segment with sharp setae on its surface. Penis lobes without spines, titillators developed (Fig. 13 f). Cercus white. Female (in ethanol) (Fig. 14). Body length 10.5 – 13.1 mm. Cercus length ca. body length x 2.1. Forewing length 12.2 – 15.1 mm. Head. Color white. Frons shape triangular. Compound eyes dark-gray to black, light-blueish gray when alive. Thorax. Coloration as in male imago (Fig. 14 a). Wings. Veins slightly brown. Basal markings as in male imago (Fig. 14 a). Legs. Coloration and markings as in male imago. Fore tarsus not elongated. Fourth tarsal segment of each leg shortest, other segments almost equal length (Figs 14 b – d). Tarsal claws dissimilar as in male imago. Abdomen. White to translucent, greenish eggs visible when alive. Posterior margin of subgenital plate almost straight. Posterior margin of sternum IX with shallow emargination and both tips relatively sharp (Fig. 14 e). Cercus white.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFADFFF8FF55FBB3FC20FA0A.taxon	diagnosis	Diagnosis and comparison. Nymph. The nymph of E. L-nigrum is quite similar to that of E. latifolium. Among our samples, the body size of E. latifolium is larger than E. L-nigrum from May to June (reaching up to 15 mm vs. 11 mm, respectively). However, in samples collected later in the season, E. latifolium individuals become smaller. The following morphological characteristics can be used to differentiate the nymphs of the two species: 1) the shape of the marginal denticles on the abdominal terga differs, with E. latifolium having short, fine denticles (Figs 7 k, 31 a) and E. L-nigrum having long, sharp denticles (Figs 12 g, 31 b); 2) the posterior tip of abdominal sternum IX is rounded in E. latifolium (Figs 7 i, j) but pointed in E. L-nigrum (Figs 12 d, e); and 3) the outer margin of the left mandible’s inner incisor lacks sharp serrations in E. L-nigrum (Figs 12 c, f) but has sharp serrations in E. latifolium (Fig. 7 c). However, it appears that characteristics 1) and 2) are reliable diagnostic features earlier in the summer, but become less distinct later in the season (after September). In this study, specimens were differentiated by a combination of these two features. The serration on the mandibles may vary depending on the time elapsed since molting, but observations of the inner cuticle of the incisor suggest that serration is consistently absent in E. L-nigrum (Fig. 12 f). This morphological trait may be useful for identifying this species, although it requires dissection and high-magnification observation. The proposed morphological description of E. L-nigrum nymphs is based on specimens identified through molecular analysis. Male imago. Distinguishing between E. L-nigrum and E. latifolium in male imago is straightforward based on their penial structures: E. L-nigrum has titillators, which are absent in E. latifolium. Additionally, E. L-nigrum lacks lateral projections, whereas E. latifolium possesses them. The black markings at the base of the forewing also differ: E. L-nigrum has " L " or " Z " - shaped markings on the costal brace and the base of the radius, while E. latifolium displays spotted markings only on the costal brace.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFADFFF8FF55FBB3FC20FA0A.taxon	discussion	Remarks. Nymph. The nymph was described for the first time. Male imago. The specimens here identified as E. L-nigrum agree with the original description (Matsumura 1931) and the syntype specimens. Female imago. The female imago was described for the first time. Subgenus attribution. This species can be attributed to the subgenus Belovius by the following features: 1) wide-rounded anal-proximal projection on gills II – VI (Fig. 11 d); 2) Male imago with titillators on its penis (a valuable character in Belovius) (Fig. 13 f) (Kluge 2004). Tshernova (1981) probably observed this species and established the subgenus Belovius. Further notes are in the discussion section. This species was originally described based on male imaginal specimens collected in " Sapporo ". The description appeared in 6000 Illustrated Insects of Japan-Empire (Matsumura 1931; 1932), a publication noted for numerous taxonomic and nomenclatural issues that have complicated species concepts for many Japanese insects due to its insufficient descriptions (see Uéno 1931 c regarding mayflies). Fortunately, we were able to examine syntypes of E. L-nigrum and found no contradictions in morphological characters among the materials examined (Fig. 33). This species was considered a synonym of E. latifolium from Imanishi (1934) onward; however, Ishiwata (2001 b) suggested that E. L-nigrum and E. latifolium could be distinguished by the shape of male genitalia, recognizing E. L-nigrum (spelled as " E. l-nigrus ") as a valid species (Ishiwata 2001 a). This study supports that view. Emergence periods and habitat. Fully mature nymphs and imagines were continuously found from June to October, suggesting that this species is multivoltine. Mature nymphs collected in May and June were relatively large (ca., 11 mm), while those obtained from August to October were smaller (ca., 8 mm). This species is most common in the midstream riffles of the Toyohira-gawa River (localities [11.] – [17.]) but is absent from smaller mountain streams (localities [10.], [19.]).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFADFFF8FF55FBB3FC20FA0A.taxon	distribution	Distribution. Japan (Hokkaido, Honshu, Shikoku, and Kyushu).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB7FFF6FF55F9BEFC20FDAF.taxon	materials_examined	Materials examined. Type specimen (Holotype): (identification label by Imanishi, 1933 " Epeorus curvatulus Matsumura, K. Imanishi, 1933 "). 1 male imago, " Tamagawa [タマガハ] 7 / 25 (year not listed) ", " Epeorus curvatulus det. Matsumura ", " Two tails color white [二 * の ¹ は ̊ e] ", " Type Matsumura " (red label), " Epeorus curvatulus Matsu. " (probably attached recently) (Fig. 34). Other specimens: JAPAN, HOKKAIDO, ISHIKARI: [1.] Sapporo-shi, Minami-ku, Jozankei, Toyohira-gawa Riv., mainstream, 678 m a. s. l. (42 ° 47 ' 57.0 " N, 141 ° 10 ' 14.3 " E), 1 mature male nymph, 15. VIII. 2003, K. Saito; [4.] Sapporo-shi, Minami-ku, Jozankei, Usubetsu-gawa Stream (a tributary of Toyohira-gawa Riv.), 472 m a. s. l. (42 ° 54 ' 33.5 " N, 141 ° 07 ' 28.9 " E), 1 mature male nymph and 2 mature female nymphs, 09. IX. 2002, K. Saito; [5.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), the confluence of Shirai-gawa Stream and Migimata-gawa Stream, 450 m a. s. l. (42 ° 59 ' 39.6 " N, 141 ° 04 ' 42.9 " E), 3 mature female nymphs, 07. VIII. 2004, K. Saito; ditto, 1 mature female nymph, 07. IV. 2019, T. Takayanagi; [8.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), 300 m a. s. l. (42 ° 58 ' 37.7 " N, 141 ° 08 ' 16.4 " E), 1 mature female nymph, 13. VIII. 2005, K. Saito; [15.] Sapporo-shi, Chuo-ku, Minami 13 - jo, Nishi 1 - chome, Toyohira-gawa Riv., mainstream, 28 m a. s. l. (43 ° 02 ' 35.3 " N, 141 ° 21 ' 31.7 " E), 1 female imago, 1 mature male nymph and 3 mature female nymphs, 19. VIII. 2020, T. Takayanagi; ditto, 1 mature male nymph and 2 mature female nymph, 25. IX. 2020, T. Takayanagi; [16.] Sapporo-shi, Chuo-ku, Kita 1 - jo, Higashi 19 - chome, Toyohira-gawa Riv., mainstream, 15 m a. s. l. (43 ° 04 ' 04.8 " N, 141 ° 23 ' 13.2 " E), 2 mature male nymphs, 02. IX. 2006, K. Saito; ditto, 1 male imago, 1 female imago, 9 mature male nymphs and 7 mature female nymphs, 21. VIII. 2021, T. Takayanagi; KAMIKAWA (outside of the study area): Kamikawa-cho, Souunkyo, Ishikari-gawa Riv., 611 m a. s. l. (43 ° 43 ' 49.2 " N, 142 ° 56 ' 34.5 " E), 1 male imago, 11. IX. 2020, T. Hirose; Horokanai-cho, Shumarinai, Shumarinaigawa Riv., 268 m a. s. l. (44 ° 17 ' 56.0 " N, 142 ° 09 ' 31.0 " E), 1 male imago, 02. VIII. 2020, T. Ito; HIYAMA (outside of the study area): Assabu-cho, Shirooka, Sasamodosawa-gawa Riv., 76 m a. s. l. (41 ° 49 ' 59.0 " N, 140 ° 19 ' 57.6 " E), 1 female imago, 08. VII. 2019, T. Takayanagi. Nymph (mature, in ethanol), redescription (Figs 15 – 17). Body length 10.0 – 11.0 mm (male), 10.0 – 12.5 mm (female). Cercus length ca. body length x 1.2. Head. Shape trapezoidal. Color dark-brown, with white spots. Compound eyes dark-gray. Ocelli dark gray. Antennae brown (Figs 16 a, c). Anterior margin very densely covered with fine medio-dorsally directed hair-like setae extending to lateral margins (Fig. 16 b). Dorsal surface covered with fine hair-like setae. Labrum: lateral margins straight and widened anteriorly, anterior margin gently concave, dorsal surface with 8 – 10 bristles anteromedially and 2 bristles near each side of anterolateral margin. Ventral surface with a row of bristles along lateral margins extending to anterior margins and fine, long hair-like setae medially (Fig. 17 a). Mandibles: each outer incisor with three apical teeth and serrated margins, inner incisor with two apical teeth (right mandible) or three apical teeth (left mandible) and serrated sharply on outer margin of both incisors, right inner incisor slender and almost straight. Tuft of long setae on the base of inner incisor of right mandible, tuft of long setae and one comb-like seta on the base of inner incisor of left mandible (Figs 17 b, c). Maxillae: one penicillate setae at base of apical tooth complex (Fig. 28 c). Hypopharynx: superlinguae distally widened. Lingua shape quadrate. Labium: labial palps two-segmented, outer margin of proximal one with sparse-thick setae. Distal segment with sparse, hair-like setae on outer surface and dense, brush-like setae on distal 1 / 3 area. Glossae and paraglossae with long, dense setae. Thorax. Color dark-brown, with pale markings dorsally (Figs 15 a, d). Ventrally white to grayish-white (Figs 15 b, e). Pronotum slightly projecting laterally (Fig. 29 b). Legs. Each femur with dark brown markings and hypodermal black spot on its middle part of anterior face (Fig. 16 d), blade-like long setae on its dorsal edge, short bluntly pointed spines on its ventral edge. Setae on femoral surface variably shaped, most oval to semi-circular (Fig. 17 d). Tibia with two dark-brown markings and long hair-like setae on dorsal edge (Fig. 16 d). Tarsus darker in proximal area and with long hair-like setae on its dorsal edge (Fig. 16 d). Tarsal claw with 3 – 4 denticles. Abdomen. Color dark-brown, each tergum with a pair of dark spots (Figs 15 a, d). Sterna white to grayish-white (Figs 15 b, e). Each tergum with long hair-like setae densely arranged along the midline. Posterior margin of each tergum without long setae and with spines of variable lengths which overlap, forming 2 – 3 levels (Figs 17 j, 31 c). Tergum I – VII each with three short postero-lateral projections, ventral and lateral ones blunt and dorsal one pointed and bending upward (Fig. 30 c). Posterior margin of sternum IX triangular, with a sharp medial emargination and with long hair-like setae from middle to lateral edges (Figs 17 h, i). Dorsal surface of cercus with a row of fine setae. Gills. Dorsally greyish to brownish, ventrally same (Fig. 16 e). Gill I extending anteriorly and meeting beneath mesothorax (Figs 15 b, e, 17 e). Posterior tip of Gill VII slightly expanded beneath sternum. Rounded projections at costal-proximal margin of gill plates II – VII (Figs 17 f, g). Costal margin with rough surface. Each gill plate with filaments forming a fan-shape together. Gill VII with longitudinal fold (Fig. 17 g). Male imago (in ethanol), redescription (Fig. 18). Body length 12.6 mm. Cercus length ca. body length x 2.5. Forewing length 14.5 mm. Head. Yellowish-white. Frons margin with brown border. Frons shape relatively round. Compound eyes dark-gray to black. Ocelli grayish-white with dark-gray border. Thorax. Ground color orange to brick-color, internal tissues visible. Pronotum without markings. Mesonotum without markings, darker in scutellum. Mesopleuron with dark markings. Metanotum dark on scutellum (Fig. 18 a). Wings. Hyaline, veins white. Pterostigmatic area cloudy. Forewing with black markings on costal brace to the base of radius and media (Fig. 18 e). Hindwing with black markings on the same part as forewing. Legs. Each femur with a black spot on the middle part. Fore tibia dark at the tip. Each segment of fore tarsus becoming shorter distally and each joint color dark. Fourth segment shortest on mid and hind tarsus, each joint color dark (Figs 18 b – d). Tarsal claws dissimilar, one hooked-shape and the other oblong. Abdomen. Ground color brownish-white to transparent, posterior margins of segments I – IX with dark-brown streaks. Segment VIII – X yellowish white, internal organs and tissues visible (Fig. 18 a). Posterior margin of styliger plate bulging, tip rounded. Projection on forceps base not developed. Forceps four segmented, distal two segments color dark. Penis lobes without spines, with complex concavity, titillators developed (Fig. 18 f). Cercus white, basally brown. Female (in ethanol), redescription (Fig. 19). Body length 11.9 mm. Cercus length ca. body length x 2.4. Forewing length 13.5 mm. Head. Yellowish-white. Frons triangular. Compound eyes dark-gray to black, grayish-green when alive. Thorax. Coloration as in male imago (Fig. 19 a). Wings. Veins dark. Markings as in male imago. Legs. Coloration and markings as in male imago. Fore tarsus not elongated. Fourth segment shortest on each tarsus, other segments almost equal length (Figs 19 b – d). Tarsal claws dissimilar as in male imago. Abdomen. Coloration and markings as in male imago. Reddish eggs visible when alive (Fig. 19 a). Posterior margin of subgenital plate quadrate, apices rounded. Posterior margin of sternum IX with medial emargination (Fig. 19 e).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB7FFF6FF55F9BEFC20FDAF.taxon	diagnosis	Diagnosis and comparison. Nymph. This species is easily distinguished from other species in the study area by 1) a strongly extended gill I (Figs 15 b, e, 17 e) and 2) a prominent dorsal projection of the postero-lateral projections located on each abdominal tergum (Fig. 30 c). Male imago. This species has black markings at the base of the forewing and has titillators on its penis, similar to E. L-nigrum, but its styliger plate is rounded, and the projection at the base of the forceps is less developed in contrast to E. L-nigrum.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB7FFF6FF55F9BEFC20FDAF.taxon	discussion	Remarks. Nymph. The specimens identified here as E. curvatulus agree with the description of Iron sp.? (Uéno 1928) which supports Imanishi (1934). Male imago. The specimens identified here as E. curvatulus agree with the original description and holotype (Matsumura 1931). Subgenus attribution. Kluge (2004) attributed this species to the subgenus Iron, but it should be placed in the subgenus Caucasiron due to the following characteristics: 1) hairs on the anterior margin of the head are directed dorsomedially (nymphs, Fig. 16 b); 2) each of gills II – VII has a well-developed projection (nymphs, Figs 16 e, 17 f, g); and 3) gill plates form a “ suction disc ” (nymphs, Figs 15 b, e). Additionally, the male imago of this species lacks latero-dorsal spines on its penis lobes. This species was originally described based on male imaginal specimens collected from the Tama-gawa River in Tokyo, Honshu (Matsumura 1931; 1932). The holotype is preserved at SEHU, and male imagines of this species can be confidently identified by comparison with the type specimen (Fig. 34). Nymphs of this species were identified using DNA barcoding, and their morphological characteristics matched those of Uéno's Iron sp.? (Uéno 1928). Although Imanishi (1934) associated Uéno's Iron sp.? with E. uenoi, the male genital structures of the type specimens of E. curvatulus (Fig. 34 e) and E. uenoi (Fig. 32 d) are markedly different, making this identification highly questionable. Ishiwata (2001 a; 2001 b; 2018) suggested there may be misidentifications in Imanishi's series of works. Emergence period and habitat. Fully mature nymphs and imagines were obtained from July to October. This species was collected from a wide area within the Toyohira-gawa River system.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB7FFF6FF55F9BEFC20FDAF.taxon	distribution	Distribution. Japan (Hokkaido, Honshu, Shikoku, and Kyushu).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB9FFF2FF55FD5AFF64FD1F.taxon	vernacular_names	[Japanese name " Yumimon-hirata-kagerou "]	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB9FFF2FF55FD5AFF64FD1F.taxon	materials_examined	Materials examined. Type specimens: We investigated The Kyoto University Museum collection but could not find the type specimen. Probably lost. Other specimens: JAPAN, HOKKAIDO, ISHIKARI: [4.] Sapporo-shi, Minami-ku, Jozankei, Usubetsu-gawa Stream (a tributary of Toyohira-gawa Riv.), 472 m a. s. l. (42 ° 54 ' 33.5 " N, 141 ° 07 ' 28.9 " E), 2 mature male nymphs, 8. IX. 2002, K. Saito; [5.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), the confluence of Shirai-gawa Stream and Migimata-gawa Stream, 450 m a. s. l. (42 ° 59 ' 39.6 " N, 141 ° 04 ' 42.9 " E), 1 mature male nymph and 1 mature female nymph, 07. VIII. 2004, K. Saito; [15.] Sapporo-shi, Chuo-ku, Minami 13 - jo, Nishi 1 - chome, Toyohira-gawa Riv., mainstream, 28 m a. s. l. (43 ° 02 ' 35.3 " N, 141 ° 21 ' 31.7 " E), 2 mature male nymphs and 4 mature female nymphs, 19. VIII. 2020, T. Takayanagi; ditto, 1 male mature nymph and 1 female mature nymph, 08. VIII. 2021, T. Takayanagi; [16.] Sapporo-shi, Chuo-ku, Kita 1 - jo, Higashi 19 - chome, Toyohira-gawa Riv., mainstream, 15 m a. s. l. (43 ° 04 ' 04.8 " N, 141 ° 23 ' 13.2 " E), 1 mature male nymph and 1 mature female nymph, 21. VIII. 2021, T. Takayanagi. Nymph (mature, in ethanol), redescription (Figs 20 – 22). Body length 11.0 mm (male), 10.0 – 12.0 mm (female). Cercus length ca. body length x 1.3 – 1.4. Head. Shape trapezoidal. Color dark-brown, with white markings. Compound eyes dark gray. Ocelli dark gray. Antennae white, basally brown or completely brown. Anterior margin densely covered with fine hair-like setae extending to lateral margins. Dorsal surface of head covered with fine hair-like setae (Figs 21 a, b). Labrum: anterior and lateral margins evenly convex, anterior margin medially concave. Ventral surface with a row of bristles along lateral margins extending to anterior margins, row of short setae and brush of median fine hair-like setae on each side. Dorsal surface with six long adjacent bristles medially and two long bristles near each side of antero-lateral margin, and scattered variable-length setae (Fig. 22 a). Mandibles: each outer incisor with three apical teeth (right mandible) or two apical teeth (left mandible) and serrated margins, inner incisor with two apical teeth (right mandible) or three apical teeth (left mandible) and outer margin of both inner incisors sharply serrated, right inner incisor slender and almost straight. Tuft of long setae on the base of inner incisor of right mandible, tuft of long setae and one plumose seta on the base of inner incisor of left mandible (Figs 22 b, c). Maxillae: One penicillate seta at base of apical tooth complex (Fig. 28 d). Hypopharynx: superlinguae distally widened, lingua subquadrate. Labium: Labial palps two segmented, outer margin of proximal one with sparse, thick setae. Distal segment with sparse, hair-like setae on outer surface and dense, brush-like setae on distal 1 / 3 area. Glossae and paraglossae with long, dense setae.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB9FFF2FF55FD5AFF64FD1F.taxon	description	Thorax. Color dark brown dorsally, white ventrally (Fig. 20). Pronotum margin roundly projecting laterally (Fig. 29 c). Legs. Each femur with dark brown markings and a hypodermal black spot on middle part of anterior face (Fig. 21 c), blade-like long setae on dorsal edge, and short bluntly pointed spines on ventral edge. Femoral setae diversely shaped: semi-oblong, maize-grain-shape or semi-circular (Fig. 22 d). Tibia with two dark-brown markings, long hair like setae on its dorsal edge (Fig. 21 c). Tarsus darker in proximal area, long hair like setae on its dorsal edge (Fig. 21 c). Tarsal claw with four small denticles. Abdomen. Terga dark-brown, each tergum with a pair of dark spots (Figs 20 a, d). Sterna white, each sternum with a pair of slightly blackish spots (Figs 20 b, e). Each tergum with a pair of rows of sparse long setae located to each side of midline. Posterior margin of each segment with several long setae and diversely shaped spines which are pointed, blunt or spatulate and arranged in an irregular line, overlapping in 2 – 3 levels (Figs 22 j, 31 d). Each of terga I – VII with three postero-lateral projections, ventral and dorsal ones blunt, lateral one short-tipped (Fig. 30 d). Posterior margin of sternum IX round with relatively rounded emargination (Figs 22 h, i). Dorsal surface of cercus with a row of fine setae. Gills. Costal and posterior half part of each gill brown (Fig. 21 d). Gill I not anteriorly elongate (Fig. 22 e). Gills II – VII oval (Figs 22 f, g). Costal margin of gill I with fine setae. Costal margin of gills II – VII with small spines and fine setae forming a rough surface. Gill II – VII with anal ribs on anal margin. Each gill plate with filaments forming a fan-shape together. Gill VII without longitudinal fold (Fig. 22 g). Imagines of this species were not obtained in this study.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB9FFF2FF55FD5AFF64FD1F.taxon	diagnosis	Diagnosis and comparison. Nymph. Gill I is not extended anteriorly, and gill VII lacks a longitudinal fold, in contrast to E. curvatulus and E. aesculus. Immature nymph’s display a blackish streak on the posterior part of each abdominal tergum, similar to E. aesculus, but this streak diminishes in mature nymphs.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB9FFF2FF55FD5AFF64FD1F.taxon	discussion	Remarks. Nymph. According to Okuma (1980) and Ishiwata et al. (2018), nymphs of this species can be distinguished from the similar species E. ikanonis Takahashi, 1924, by the length of the cerci and seasonal growth patterns. In E. ikanonis, the cerci length is roughly equal to the body length, whereas in E. nipponicus, it is about 1.5 times the body length. Mature nymphs of E. ikanonis are observed from winter to early spring, while those of E. nipponicus appear in autumn. Subgenus attribution. Our observation fully supports the classification by Ma et al. (2021) which assigned this species to the subgenus Proepeorus based on male imaginal characteristics. Nymphs of this subgenus are characterized by the following features: 1) gills II – VII possess an anal rib along the anal margin; 2) gill I is not elongated; and 3) gill VII lacks a longitudinal fold (Kluge 2004). The subgenus Epeorus s. str. (= Epeorus / fg 4) also shares these traits, with male imaginal penial structures being the only distinguishing feature between Proepeorus and Epeorus s. str. The taxonomic status of this species has been ambiguous. Uéno (1931 a) first described the species based on material collected from the Nakabusa-gawa River in Nagano, central Honshu. However, the type specimens were likely lost (Author's investigation 2019). Imanishi (1934) included this species in his monograph without any accompanying explanation. Since then, it has been omitted from major works, such as Gose's monograph on Japanese mayflies (Gose 1979). Ishiwata (2001 a; 2018) listed the species as valid and described its diagnostic characters (Ishiwata 2002; Ishiwata et al. 2018), which allowed for its identification. The nymphal morphology of this species, in its current sense, closely aligns with Imanishi's (1934) description of E. curvatulus, suggesting that E. nipponicus may have been misidentified as E. curvatulus in Imanishi's work. Ma et al. (2021) published a revision of Epeorus (Proepeorus) in China, providing a detailed description of the morphology of E. nipponicus. The nymphal morphology observed, particularly the structure of the mouthparts and the posterior margin of the abdominal terga, aligns closely with our observations. A similar species, E. anatolii Sinitshenkova, 1981, was described from Far East Russia based on female nymphs, and the description aligns completely with our observations. Bae et al. (1998) later synonymized this species with E. curvatulus, likely based on Imanishi’s concept, which may have confused E. curvatulus with E. nipponicus. However, the nymphal morphologies of E. curvatulus and E. nipponicus are distinctly different, suggesting that E. anatolii should potentially be synonymized with E. nipponicus. Nevertheless, confirming this requires examination of the type specimens of E. anatolii, as also discussed by Ma et al. (2021). Emergence periods and habitat. Mature nymphs were obtained after August in the study areas. This species was obtained from a wide area within the Toyohira-gawa River system.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFB9FFF2FF55FD5AFF64FD1F.taxon	distribution	Distribution. Japan (Hokkaido, Honshu, Shikoku, and Kyushu), Korea, China (Northeast), and Russia (Far East).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFBDFFCEFF55FCAAFF64F8F4.taxon	materials_examined	Materials examined. Type specimens: We could not find the holotype at The Kyoto University Museum in 2019. Probably lost. Other specimens: JAPAN, HOKKAIDO, ISHIKARI: [1.] Sapporo-shi, Minami-ku, Jozankei, Toyohira-gawa Riv., mainstream, 678 m a. s. l. (42 ° 47 ' 57.0 " N, 141 ° 10 ' 14.3 " E), 3 mature male nymphs and 2 mature female nymphs, 11. VI. 2003, K. Saito; [2.] Sapporo-shi, Minami-ku, Jozankei, Izarisawa-gawa Stream (a tributary of Toyohira-gawa Riv.), 568 m a. s. l. (42 ° 51 ' 18.4 " N, 141 ° 10 ' 34.0 " E), 53 mature male nymphs and 44 mature female nymphs, 14. VI. 2007, K. Saito; [4.] Sapporo-shi, Minami-ku, Jozankei, Usubetsu-gawa Stream (a tributary of Toyohira-gawa Riv.), 472 m a. s. l. (42 ° 54 ' 33.5 " N, 141 ° 07 ' 28.9 " E), 5 mature male nymphs, 06. VII. 2002, K. Saito; [5.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), the confluence of Shirai-gawa Stream and Migimata-gawa Stream, 450 m a. s. l. (42 ° 59 ' 39.6 " N, 141 ° 04 ' 42.9 " E), 5 mature male nymphs and 4 mature female nymphs, 06. VI. 2004, K. Saito; ditto, 1 immature nymph, 07. IV. 2019, T. Takayanagi; [6.] Sapporo-shi, Minami-ku, Jozankei, Otarunai-gawa Stream (a tributary of Toyohira-gawa Riv.), 502 m a. s. l. (43 ° 04 ' 22.4 " N, 141 ° 06 ' 34.8 " E), 8 mature male nymphs and 15 mature female nymphs, 11. V. 2002, K. Saito; [8.] Sapporo-shi, Minami-ku, Jozankei, Shirai-gawa Stream (a tributary of Toyohira-gawa Riv.), 300 m a. s. l. (42 ° 58 ' 37.7 " N, 141 ° 08 ' 16.4 " E), 6 mature male nymphs and 8 mature female nymphs, 14. VI. 2005, K. Saito; [10.] Sapporo-shi, Minami-ku, Toyama, Kannonzawa-gawa Stream (a tributary of Toyohira-gawa Riv.), 267 m a. s. l. (42 ° 58 ' 31.0 " N, 141 ° 15 ' 30.0 " E), 9 male imagines and 2 female imagines, 23. V. 2019, T. Takayanagi; ditto, 5 mature male nymphs and 1 mature female nymph, 10. V. 2020, T. Takayanagi; ditto, 1 female imago, 29. V. 2020, T. Takayanagi; [11.] Sapporo-shi, Minami-ku, Toyotaki, Toyohira-gawa Riv., mainstream, 188 m a. s. l. (42 ° 57 ' 38.4 " N, 141 ° 13 ' 50.9 " E), 1 mature male nymph, 14. VI. 2005, K. Saito; [13.] Sapporo-shi, Minami-ku, Makomanai, Toyohira-gawa Riv., mainstream, 68 m a. s. l. (42 ° 59 ' 58.5 " N, 141 ° 20 ' 26.0 " E), 1 mature male nymph, 26. VI. 2006, K. Saito; [15.] Sapporo-shi, Chuo-ku, Minami 13 - jo, Nishi 1 - chome, Toyohira-gawa Riv., mainstream, 28 m a. s. l. (43 ° 02 ' 35.3 " N, 141 ° 21 ' 31.7 " E), 1 mature male nymph, 16. V. 2020, T. Takayanagi; [18.] Sapporo-shi, Nishi-ku, Heiwa, Kotonihassamu-gawa Stream (a tributary of Shin-kawa Riv.), 312 m a. s. l. (43 ° 03 ' 25.3 " N, 141 ° 12 ' 40.6 " E), 4 mature male nymphs and 4 mature female nymphs, 03. V. 2020, T. Takayanagi; [19.] Chitose-shi, Shikotsuko-onsen, Shirisetsunai-gawa Stream (an inlet stream of Lake Shikotsu-ko), 289 m a. s. l. (42 ° 46 ' 39.0 " N, 141 ° 24 ' 05.8 " E), 1 mature male nymph, 23. V. 2019, T. Takayanagi; ditto, 6 female imagines and 1 mature male nymph, 01. VI. 2021, T. Takayanagi; [20.] Chitose-shi, Bifue, Bifue-gawa Stream (an inlet stream of Lake Shikotsu-ko), 257 m a. s. l. (42 ° 43 ' 47.9 " N, 141 ° 15 ' 18.2 " E), 1 mature female nymph, 07. IV. 2019, T. Takayanagi; OKHOTSK (outside of the study area): Engaru-cho, Mt. Hirayama, small stream flowing into Shiyuubetsu-gawa Riv., 1164 m a. s. l. (43 ° 46 ' 15.6 " N, 143 ° 01 ' 43.5 " E), 5 male imagines, 12. VII. 2018, T. Takayanagi. Nymph (mature, in ethanol), redescription (Figs 23 – 25). Body length 8.1 – 9.0 mm (male), 8.3 mm (female). Cercus length ca. body length x 1.1. Head. Shape trapezoidal. Color pale-brown to dark-brown, with white markings. Compound eyes dark gray. Ocelli dark gray. Antennae brown. Anterior margin densely covered with fine hair-like setae extending to lateral margins. Dorsal surface of head covered with fine hair-like setae (Figs 24 a, b). Labrum: anterior and lateral margins evenly convex, anterior margin gently concave. Ventral surface with a row of bristles along lateral margins extending to anterior margins, with a row of short setae and brush of median fine hair-like setae on each side. Dorsal surface with six widely spaced long bristles medially, two long bristles near side of each antero-lateral margin, and scattered setae of variable lengths (Fig. 25 a). Mandibles: each outer incisor with two apical teeth and serrated margins, inner incisor both straight with two apical teeth (right mandible) or three apical teeth (left mandible) and sharply serrated on outer margin of both incisors. Tuft of long setae on the base of both incisors and one brachy-pulmose seta on the base of left incisor (Figs 25 b, c). Maxillae: One penicillate seta and one or two long, thick setae at base of apical tooth complex (Fig. 28 e). Hypopharynx: Superlinguae distally widened. Lingua subquadrate. Labium: labial palps two segmented, outer margin of proximal one with sparse-thick setae. Distal segment with sparse, hair-like setae on outer surface and dense, brush-like setae on distal 1 / 3 area. Thorax. Dorsally pale-brown to dark-brown, ventrally white (Fig. 23). Pronotum slightly expanded laterally (Fig. 29 d). Blackish spot on propleuron, just posterior to fore coxa (Figs 23 c, f). Legs. Each femur with dark brown markings and a hypodermal black spot on middle part of anterior face (Fig. 24 c), blade-like long setae on dorsal edge, short bluntly pointed spines on ventral edge. Femoral setae dense and diversely shaped: semi-oblong, oval, semi-circular or spatulate (Fig. 25 d). Tibia with two dark-brown markings, long hair-like setae on its dorsal edge (Fig. 24 c). Tarsus darker in proximal area, with long hair-like setae on its dorsal edge (Fig. 24 c). Tarsal claw with 3 – 4 small denticles. Abdomen. Terga pale-brown to dark-brown, each tergum with a pair of dark obscure spots. Terga I – VII have a black streak on both latero-posterior edges (Figs 23 a, d). Sterna yellowish-brown (Figs 23 b, e). Each tergum with dense, long hair-like setae on the surface of midline. Posterior margin of each tergum without long setae, with short, blunt spines which overlap in 3 – 4 levels (Figs 25 j, 31 e). Each tergum I – VII with three postero-lateral projections, ventral and dorsal ones blunt and lateral one short-tipped (Fig. 30 e). Posterior margins of sternum IX rounded with deep and wide medial emargination, covered with long hair-like setae (Figs 25 h, i). Dorsal surface of cercus with a row of fine setae. Gills. Color whitish or pale brownish, costally brown (Fig. 24 d). Gill I slightly expanded anteriorly (Figs 24 d, 25 e). Gills II – VII oval (Figs 24 d, 25 f, g). Costal margin of gill I with fine setae. Costal margin of gills II – VII with small spines and fine setae forming a rough surface. Each gill plate with filaments forming a fan-shape together. Gill VII with longitudinal fold (Fig. 25 g). Male imago (in ethanol), redescription (Fig. 26). Body length 9.1 – 10.9 mm. Cercus length ca. body length x 3.2. Forewing length 10.0 – 12.3 mm. Head. Yellowish-brown. Frons shape triangular. Compound eyes dark-gray, light-blueish-gray when alive. Ocelli grayish-white with dark-gray border. Thorax. Ground color yellowish-brown, internal tissues visible. Pronotum, mesonotum and metanotum without markings. Distinct blackish spot on posterior part of propleuron. Meso- and meta-pleura without markings (Fig. 26 a). Wings. Hyaline. Forewing veins white, subcosta to radius slightly dark colored, pterostigmatic area cloudy. No markings on both fore and hindwing (Fig. 26 e). Legs. Anterior face of each femur with black spot on middle part and blurred black line on proximal half. Joints of fore tibiae and tarsi dark. Fore tarsal segments becoming shorter distally, each joint dark. Tarsal claws dissimilar, one hooked-shape and the other oblong (Figs 26 b – d). Abdomen. Yellowish brown, transparent. Posterior margin of terga I – IX edged with black streaks which are darker laterally (Fig. 26 a). Posterior margin of styliger plate rounded, without projection on forceps base. Penis lobes with proximally oriented spines and complex projections, titillators developed, curved outward (Fig. 26 f). Cercus brown. Female imago (in ethanol), redescription (Fig. 27). Body length 8.3 – 8.4 mm. Cercus length ca. body length x 2.3. Forewing length 10.0 – 11.6 mm. Head. Yellowish-white. Compound eyes gray to dark-gray. Ocelli as in male imago. Thorax. Coloration as in male imago (Fig. 27 a). Wings. Veins darker than males (Fig. 27 a). Legs. Coloration and markings as in male imago. Fore tarsus not elongated. Fourth segment of each tarsus shortest, other segments almost equal lengths. Tarsal claws dissimilar as in male imago (Figs 27 b – d). Abdomen. Coloration and markings as in male imago. Eggs yellowish and visible when living. Posterior margin of subgenital plate rounded. Posterior margin of sternum IX with deep and wide emargination (Fig. 27 e).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFBDFFCEFF55FCAAFF64F8F4.taxon	diagnosis	Diagnosis and comparison. Nymph. This species and E. curvatulus both have anteriorly extended gill I; however, in this species, the gills do not meet beneath the mesothorax. Male Imago. Wings without black markings. Penis has titillators and well-developed latero-dorsal spines. There are no similar species in the study area.	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFBDFFCEFF55FCAAFF64F8F4.taxon	discussion	Remarks. Nymph. The specimens identified here as E. aesculus match the original description by Imanishi (1934). Imanishi described two forms of this species based on the shape of gill I: a " small gill type " and a " large gill type. " The specimens examined in this study correspond to the former. No similar species are found in the study area. Imagines. The specimens identified here as E. aesculus agree with the original description (Imanishi 1934). Subgenus attribution. This species should be classified under the subgenus Iron based on the following features: 1) gill I is expanded anteriorly in the nymphal stage (Figs 24 d, 25 e); 2) hairs on the anterior margin of the head are directed forward in the nymphal stage (Figs 24 a, b); and 3) the male imago has a penis with titillators and well-developed latero-dorsal spines (Fig. 26 f) (Kluge 2004). This species was originally described based on male imaginal, female imaginal, subimaginal, and nymphal specimens collected in the Goro-sawa Valley, Toyama, central Honshu (Imanishi 1934). Although the type specimens were lost, specimens likely identified by Imanishi himself are available in the collection of The Kyoto University Museum (Author's investigation 2019). Imanishi (1934) described two types of nymphal gill I shapes, a " small-sized " type and a " large-sized " type, and the specimens observed in this study corresponding to the former. This variation may represent two different species, with the " small-sized " type corresponding to E. (Iron) aesculus and the " large-sized " type to E. (I.) maculatus Tshernova, 1949 (Sinitshenkova 1978). Kluge & Tiunova (1989) reviewed Asian species and recognized three distinct species: E. (I.) aesculus, E. (I.) maculatus, and E. (I.) alexandri Kluge & Tiunova, 1989. The morphological descriptions of E. (I.) aesculus by Sinitshenkova (1978) and Kluge & Tiunova (1989) align with E. (I.) aesculus as described here, with only a slight difference in coloration. Emergence periods and habitat. Imagines emerge from May to June in the study areas. This species is mostly caught in mountain streams (localities [1.], [2.], [4.] – [6.], [8.], [10.], [18.] – [20.]).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
C700DE52FFBDFFCEFF55FCAAFF64F8F4.taxon	distribution	Distribution. Japan (Hokkaido, Honshu, Shikoku, and Kyushu), Korea, China (Northeast), and Russia (Far East).	en	Takayanagi, Tatsushi, Yoshizawa, Kazunori (2025): Taxonomic review of Epeorus s. l. Eaton, 1881 (Ephemeroptera: Heptageniidae) in Sapporo City and adjacent areas, Hokkaido, Japan. Zootaxa 5594 (1): 1-49, DOI: 10.11646/zootaxa.5594.1.1, URL: https://doi.org/10.11646/zootaxa.5594.1.1
