The Real Characters of Heptagenia ngi Hsu (1936) from China Representing a New Genus (Ephemeroptera: Heptageniidae)

Abstract

A very common and early named mayfly species from China, Heptagenia ngi Hsu, 1936, has no exact descriptions of its imago nor nymph, so its generic status is not clear. Based on detailed re-descriptions and pictures of all its stages from fresh materials, it is transferred into a new genus Maculogenia Zhou, gen. nov. Its nymph has conspicuous pale-dark colored body, slightly concave posterior margin of head, scattered simple setae on ventral maxillae, spines and very fine hair-like setae on caudal filaments. Similarly, its imago also has remarkable dark stripes and dots on the pale body, small median titillators and short first segment of foretarsi, apically expanded penes without any spines. It is similar to the genera Electrogena, Thamnodontus, and Parafronurus but they can be differentiated easily by above selected key structures.