Epeorus Eaton, 1881 is a diverse mayfly genus in Heptageniidae comprising more than 100 species which are further divided into nine subgenera and several species groups. However, the classification and the phylogenetic relationships among them are still uncertain. Here, 15 complete mitochondrial genomes of Epeorus were sequenced and compared together with six available ones of same genus in the NCBI database. Based on morphological classification, the 21 mitogenomes were classified into six subgenera (Proepeorus, Epeorus s.str., Belovius, Iron, Caucasiron and Siniron) and four species groups (G1, G2, montanus and longimanus). Among all analyzed mitogenomes, the gene rearrangement of trnI-trnM-trnQ-NCR-ND2 was first found occurring in three species of group G1, whereas the gene block trnI-trnM-trnQ-trnM-ND2 was observed in all other mitogenomes of Epeorus. Furthermore, the genetic composition and codon usage of species in group G1 were also significantly different from all other Epeorus species, except group longimanus. The intergenic spacer between trnA and trnR, which has the stem-loop secondary structure, occurred in all 21 mitogenomes, and the sequences of stems and loops were conserved within species groups. Furthermore, the phylogenetic analyses strongly support the monophyly of all species groups, although three of six recognized subgenera Proepeorus, Belovius, and Iron, were shown as the non-monophyletic groups.

The monotypic family Deuterophlebiidae of China was recorded twice previously from far northwest upon adults, the most parts of this country have not been investigated, leaving a huge blank of knowledge on their morphology, diversity, biology, or distribution. After deliberated collecting and rearing in recent years, we obtained more than one thousand specimens of Deuterophlebiidae, they are classified into five new species herein: Deuterophlebia sinensis sp. nov., D. yunnanensis sp. nov., D. wuyiensis sp. nov., D. acutirhina sp. nov. and D. alata sp. nov. Detailed descriptions and photographs of gathered life stages are given for these new species. Adults of them can be identified by chaetotaxy and length ratio of flagellomeres and legs, microtrichia on postgena and shape of their clypeus, pupae can be recognized by thoracic spines and abdominal chitin bands, and larvae can be separated by setae on thorax and abdomen. Genetic distances between species are 0.086–0.175 based on their COI genes. This contribution represents the first database of the enigmatic Deuterophlebiidae from China and shows a new distribution pattern of Deuterophlebia. In addition, the discovery throws some light on the origin and biogeography of the genus and family.

The newly collected imaginal materials of the species Neoephemera projecta Zhou and Zheng, 2001 from Southwestern China, which is linking the other genera of the family Neoephemeridae, are described in detail. Nymphs are also photographed for the first time. The morphology of this species shows some characters of the other genera in Neoephemeridae and several autapomorphies. However, most characters can be seen as plesiomorphies of the family. Specifically, the dorsal-oriented fimbriate gills, projected frons and slim labial palpi in nymphs plus large reddishly pigmented wings, many crossveins, 4-segmented forceps with a relatively long basal segment, fused penes and unforked anal vein show that this species is closer to the taxon Fossoriae rather than to the previously considered Potamanthidae. To reflect its primitive position, a new genus, Pulchephemera Zhou gen. n., is established for this species, Pulchephemera projecta comb. n. Its eggs and observed biology are also described.

The genus Epeorus Eaton, 1881 is diverse in China but has never been specifically studied before. In this revision, eight species in Epeorus (Proepeorus) from China are recognised, including two new species, Epeorus (Proepeorus) gibbus sp. nov., Epeorus (Proepeorus) falcatus sp. nov. and additional five new records for this country. Both new species have unique shape of imaginal penis and tubercles on nymphal terga. The variation of Epeorus (Proepeorus) in China shows this subgenus may not be a monophyletic taxon. urn:lsid:zoobank.org:pub:5A151309-603F-4196-8FCC-A2DA90D7F58F

Epeorus (Belovius) carinatus Braasch & Soldán, 1984 was thought to be distributed only in Vietnam until it was recently reported in southern China. However, some morphological variations are also recognized among its Chinese populations. Here, an integrative taxonomic approach, which is combined with genetic analysis based on COI (mtDNA) and morphological evidence, is used to investigate the variation of this species in China. The results show that E. (B) carinatus previously reported in China actually comprises two species: the originally identified E. (B) carinatus and a new species, E. (B.) dentatus sp. nov. Both male imaginal and nymphal stages of two species are described herein. Morphologically, these two species can be distinguished from each other by (1) nymphal labrum and mandible, (2) coloration of abdominal terga on both male imaginal and nymphal stages, (3) coloration of wings and (4) shapes of genitalia of male imagines.