Identification guide to larvae of Caucasian Epeorus (Caucasiron) (Ephemeroptera, Heptageniidae) Author Hrivniak, Ľubos Biology Centre of the Czech Academy of Sciences, Institute of Entomology, Branisovska 31, 37005 Ceske Budejovice, Czech Republic & Faculty of Sciences, University of South Bohemia, Branisovska 31, 37005 Ceske Budejovice, Czech Republic lubos.hrivniak@gmail.com Author Sroka, Pavel Biology Centre of the Czech Academy of Sciences, Institute of Entomology, Branisovska 31, 37005 Ceske Budejovice, Czech Republic https://orcid.org/0000-0003-4367-6564 Author Bojkova, Jindriska Department of Botany and Zoology, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic Author Godunko, Roman J. Biology Centre of the Czech Academy of Sciences, Institute of Entomology, Branisovska 31, 37005 Ceske Budejovice, Czech Republic & Department of Invertebrate Zoology and Hydrobiology, University of Lodz, Banacha 12 / 16, 90237 Lodz, Poland https://orcid.org/0000-0003-2196-3327 godunko@seznam.cz text ZooKeys 2020 986 1 53 http://dx.doi.org/10.3897/zookeys.986.56276 journal article http://dx.doi.org/10.3897/zookeys.986.56276 1313-2970-986-1 CDFA38CA1B6F424D85246B540E63E954 2A3CD185EDDF52BDB0AD1E5DA924299B Epeorus (Caucasiron) alborzicus Hrivniak & Sroka, 2020 Figs 39 , 40 , 41 Type locality. Iran, Mazandaran Province, Panjab village, unnamed brook (left tributary of Haraz River); 36°05'52.818"N / 52°15'15.987"E (locality no. 152); 955 m a.s.l. Distribution. Northern Iran. Species endemic to the Alborz Mountains (Fig. 39 ). Habitat. Larvae inhabit small rivers at middle and high altitude in the central Alborz. Altitudinal range of sampling sites 750-2438 m a.s.l. (Fig. 39 ). Most frequently found at altitudes above 1000 m a.s.l. At high altitudes often syntopic with E. (C.) iranicus . Main morphological diagnostics of larvae. (i) abdominal terga as on Fig. 40H, I ; (ii) abdominal sterna II-VI with circular central medial macula of various intensity (Fig. 40B, L-N ); (iii) tergum X with postero-lateral projections (Fig. 41K , arrow), (iv) femora without medial hypodermal spot (Fig. 40F, G ); (v) gill plates VII (in natural position from ventral view) wide (Figs 40J, K , 41H-J ); (vi) setae on abdominal terga hair-like (Fig. 41E ); (vii) gill plates III with well-developed projection (Fig. 41G ). Remarks. Taxonomy . This species was described based on larvae collected from Alborz Mts. ( Hrivniak et al. 2020a ). Imagines not described. The type series is currently deposited in SMNS, IECA, and Natural History Museum and Genetic Resources, Department of Environment, Tehran, Iran (MMTT_DOE). Figure 39. Geographical (left) and vertical (right) distribution of Epeorus (Caucasiron) alborzicus . Figure 40. Epeorus (Caucasiron) alborzicus , larva: A habitus in dorsal view B habitus in ventral view C habitus in lateral view D head of male in dorsal view E head of female in dorsal view F, G middle leg in dorsal view H, I abdominal terga J, K gills VII (in natural position from ventral view) L-N abdominal sterna II-VI. Figure 41. Epeorus (Caucasiron) alborzicus , larva: A labrum (left half in dorsal view right half in ventral view) B incisors of left mandible C incisors of right mandible D setae on dorsal surface of femora E surface and posterior margin of abdominal tergum VII F gill I G gill III H gill VII (flattened on slide) I, J gill VII (in natural position from ventral view) variability in shape K abdominal segments VIII-X in lateral view (arrow points on postero-lateral projection) L sternum IX of female with observed variability.