A Review of the Genus Cloeon from Chinese Mainland (Ephemeroptera: Baetidae)

SIMPLE SUMMARY: The mayflies of baetid genus Cloeon Leach, 1815 are common inhabitants of lentic environments, such as ponds, lakes, reservoirs, and even some temporary bodies of water near human communities. Therefore, they are frequently collected and comprehensively researched around the world. In China, however, although nine Cloeon species names have been reported, few of them are confirmed historically. In this study of over 1000 specimens from over 50 sites on the Chinese mainland, four species of Cloeon were identified, namely C. bicolor Kimmins, 1947, C. dipterum (Linnaeus, 1761), C. harveyi (Kimmins, 1947), and C. viridulum Navás, 1931. The record of C. bicolor is the first in China, and its nymphs are described for the first time. Three junior synonyms are proposed for the species C. viridulum. The present research is not only a revised review of the genus Cloeon for the Chinese mainland but also a solid base for future works on Chinese and Asian Cloeon taxonomy. ABSTRACT: The widely distributed and species diverse genus Cloeon Leach, 1815 has never been reviewed in China, although nine species names have been reported from this country. After checking types of two species (C. viridulum and C. apicatum) and newly collected materials from more than 50 sites, four species are recognized, compared, and photographed in this research. Among them, the species C. bicolor Kimmins, 1947 is first recorded in China, and its nymphs are described for the first time. The distribution in China of two other species (C. dipterum (Linnaeus, 1761) and C. harveyi (Kimmins, 1947)) are also confirmed. The two species established by Navás (C. apicatum Navás, 1933 = C. navasi Bruggen, 1957, C. pielinum Navás, 1933, syn. nov.) and the species C. micki named by Tong and Dudgeon in 2021 are synonymized with C. viridulum Navás, 1931—the fourth species in this study. Furthermore, the C. virens Klapálek, 1905 from the Chinese mainland, found by Ulmer in 1925, is also regarded as the last species. Among the four species, the C. dipterum and C. harveyi seem closer because of the similar female color patterns of their stigma and ventral abdomen, while the species C. viridulum and C. bicolor are more alike because they have neither pigmented stigma nor stripes on abdominal sterna.