The genusCentroptellaBraasch & Soldán, 1980 is accepted here in a wide sense, i.e., includingChoprallaWaltz & McCafferty, 1987. This genus concept is similar to the concept of the genusBungonaHarker, 1957 proposed by Salles et al. (2016), but with the generic nameCentroptellainstead ofBungona. The type species ofBungona,B. narillaHarker, 1957, has an unknown systematic position; the neotype designation proposed by Suter and Pearson (2001) is invalid, being inconsistent with the International Code of Zoological Nomenclature; the species nameB. narillaand the generic nameBungonaarenomina dubia, so the nameCentroptellais the senior name for the genus under consideration. The generic namesChoprallaandCrassolusSalles, Gattolliat & Sartori, 2016 both are junior synonyms ofCentroptella(syn. nov.). The subgeneraBungona,CentroptellaandChoprallaproposed by Salles et al. (2016) are unnatural. The following new combinations are proposed:Centroptella bintang(Marle, Salles & Gattolliat, 2016)comb. nov.,Centroptella bifida(Shi & Tong, 2019)comb. nov.,Centroptella fusina(Tong & Dudgeon, 2003)comb. nov.,Centroptella fustipalpus(Lugo-Ortiz & McCafferty, 1998)comb. nov.,Centroptella illiesi(Lugo-Ortiz & McCafferty, 1998)comb. nov.,Centroptella inzingae(Crass, 1947)comb. nov.,Centroptella papilionodes(Marle, Salles & Gattolliat, 2016)comb. nov.,Centroptella pontica(Sroka, Godunko & Gattolliat, in Sroka et al. 2019)comb. nov.,Centroptella ovata(Shi & Tong, 2019)comb. nov.,Centroptella quadrata(Shi & Tong, 2019)comb. nov.andCentroptella saxophila(Agnew, 1961)comb. nov.The two Australian species,C. fustipalpusandC. illiesi, differ from each other in the shape of tergalii; corrections to the original description ofC. fustipalpusare given based on re-examination of the holotype and paratypes; details of larval structures ofC. illiesiare figured. Corrections to the former descriptions of the South African speciesC. inzingaeandC. saxophilaare given. Examination of type material led to the discovery that the original description of the Oriental speciesCentroptella liebenauaeSoldán, Braasch & Muu, 1987 was based on two different species: the descriptions of imago and subimago belong toCentroptella longisetosaBraasch & Soldán, 1980 (the type species ofCentroptella), and the description of larva belongs to a different species, which we describe here asCentroptella ingridaesp. nov.The holotype ofC. liebenauae, a larva, should be considered lost; based on the date of collection, it belonged toC. longisetosa; a set of larval exuviae with the same collecting data as the holotype, is designated as the neotype ofC. liebenauae, and a new synonymy is established:C. longisetosa=C. liebenauaesyn. nov.The larvae originally assigned toC. liebenauaeare placed to a new speciesCentroptella ingridaesp. nov.belonging to theinzingae-ingridaespecies group; all stages of development of this species are described based on male and female imagines reared from larvae in Thailand and on the misidentified paratypes ofC. liebenauaefrom Vietnam.Centroptella longisetosais redescribed based on the single paratype from China, the neotype and paratypes ofC. liebenauaefrom Vietnam, and additional material from India. Additional data on the holotype ofCentroptella colorataSoldán, Braasch & Muu, 1987 are given.

The new species Epeorus (Caucasiron) bicolliculatus sp. nov. is described based on larvae and adults. Diagnostic characters are given with regard to the related species. The most pronounced difference is represented by protuberances on larval abdominal terga II–IX, present exclusively in E. (C.) bicolliculatus sp. nov. Primary data on the biology and distribution of the new species are also provided. Delimitation of the new species is verified by the analysis of COI (barcode) sequences. Barcode data for all Caucasian species of the subgenus Caucasiron are provided for the first time and compared with E. (C.) bicolliculatus sp. nov.

Combining morphological and molecular data in an integrative approach, three new mayfly species of Epeorus (Caucasiron) are described. These include Epeorus (Caucasiron) alborzicus Hrivniak & Sroka, sp. nov. and Epeorus (Caucasiron) shargi Hrivniak & Sroka, sp. nov. from northern Iran, and Epeorus (Caucasiron) zagrosicus Hrivniak & Sroka, sp. nov. from central Iran. They are unambiguously delimited using both distance-based and likelihood-based approaches in the analyses of barcode COI sequences. Each new species is compared with other species of the subgenus and morphological diagnostic characters are provided. Based on extensive sampling of streams throughout the country, the distribution and habitat preferences of all Caucasiron species in Iran are assessed. Altogether, there are now six species recorded, among them also E. (C.) nigripilosus Sinitshenkova, 1976 is reported for the first time in Iran. Five species are distributed in the Alborz Mts. in northern Iran, one species was found in the Zagros Mts. in central Iran.

Epeorus (Caucasiron) turcicus sp. nov. is described based on larvae from NE Turkey. The new species can be distinguished from other Caucasiron by a unique combination of several diagnostic characters: the presence of a rounded hypodermal medial femur spot, colouration of abdominal terga and sterna, narrow gill plate VII, fine hair-like setae on the surface of abdominal terga, and absence of postero-lateral projections on tergum X. In addition to morphological analysis, two single-locus analytical approaches are employed for delimiting the new species using COI sequences (Automatic Barcode Gap Discovery, ABGD; and General Mixed Yule Coalescent Model, GMYC). Both approaches unambiguously recognized E. (C.) turcicus sp. nov. as a distinct species. Our molecular dataset contains all Caucasiron species occurring in the Caucasus and the delimitation of individual species mostly follows the morphologically defined species. This study confirms the suitability of the GMYC approach for species delimitation within Caucasiron.

An initial checklist of mayflies (Ephemeroptera) of Iran is compiled based on critical review of available literature data, complemented with new data from 38 localities of Gilan and Ardabil provinces. At present, altogether only 46 species and 25 genera are known from Iran, 18 species are reported as new to Iran in this study. Some previously published data are critically evaluated and doubtful taxa are excluded from the list. Basic analysis of the distribution and biogeography of recorded species is given. Procloeon (Pseudocentroptilum) caspicum Sroka, sp. n. is described based on mature larva and egg. Critical differential diagnostic characters distinguishing the species from related taxa are discussed in detail.

We provide the first commented checklist of Armenian mayflies, based on all relevant literature and recent extensive sampling of 72 localities throughout Armenia during 2011, 2014, and 2015. Altogether 46 species are listed, eight of them reported from Armenia for the first time. One new species, Ecdyonurus (Ecdyonurus) eurycephalus sp. nov. is described (larva and male imago) based on morphological and molecular (COI) data. The species is characterized by a unique head shape in male imago and by the presence of tracheal filaments on gill plate VII in the larval stage.