Isonychiidae

Adults distinguished by brush-like or hairy legs, a trait reflected in the common name. Species-level identification relies on male genitalia morphology, particularly penes shape (triangular in I. kiangsinensis versus cylindrical in I. guixiensis), body coloration patterns (pink/reddish in I. kiangsinensis versus brown in I. guixiensis and I. ignota), and wing transparency. Nymphs possess gill relics on the forecoxae.

Flowing freshwater habitats including streams, creeks, and rivers. Nymphs occur on rocky substrates in water bodies. Specific collection sites include montane streams at approximately 880 m elevation, nature reserve waters, and forest farm locations.

Widely distributed across the Holarctic and Oriental regions. In China: Jiangxi, Hainan, Zhejiang, Anhui, Fujian, and Guizhou provinces; also northeastern China. Additional records from Mongolia, Russia, and Western Europe. North American distribution includes Vermont and other United States locations.

Hemimetabolous development with aquatic nymphal (larval) stage and terrestrial winged adult stage. Life stages include larva, subimago, and imago. Mature nymphs can be reared in captivity with creek water to obtain adults. Eggs dissected from female imagos for study.

Adults attracted to light sources, facilitating collection with light traps. Nymphs inhabit rocky substrates in flowing water.

Relatively large and common aquatic insects in suitable habitats; among the earliest reported mayfly species in Chinese faunal surveys. Abundant at almost all sampling sites where they occur.

Used as indicators in freshwater biomonitoring due to sensitivity to water quality. Collected for taxonomic research and phylogenetic studies using molecular markers (COI, 16S).

• HeptageniidaeBoth families belong to superfamily Heptagenioidea and share flattened body forms adapted to flowing water; Isonychiidae distinguished by brush-like legs and gill relics on forecoxae in nymphs
• BaetidaeBoth are common mayfly families in running waters; Isonychiidae nymphs are larger and possess distinctive gill structures on forecoxae absent in Baetidae

• mayflies
• aquatic insects
• freshwater
• Holarctic
• Oriental
• China
• streams
• brush-legged

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Discovery of a new Isonychia species with distinctive characters from southwestern China, and preliminary exploration of its phylogenetic status (Ephemeroptera, Isonychiidae).
• A preliminary review of Isonychia Eaton, 1871 from Chinese mainland with a re-description of I.kiangsinensis Hsu, 1936 (Insecta, Ephemeroptera, Isonychiidae).