Two New Species and First Stage Associations for Two Other Species of the <i>Cincticostella nigra</i> (Uéno, 1928) Complex (Ephemeroptera, Ephemerellidae) from Yunnan, China, with Discussion About <i>Cincticostella</i> Allen, 1971 Species Complexes Based on Winged Stages.

Abstract

Four species of the <i>Cincticostella nigra</i> (Uéno, 1928) complex (Ephemeroptera, Ephemerellidae) from Yunnan, China are described based on egg chorionic structure and nymph and winged stages, including <i>C. wangi</i> Selvakumar Martynov & Subramanian, 2021, <i>C. funki</i> Martynov, Selvakumar, Palatov & Vasanth, 2021, and two new species, viz., <i>Cincticostella xiazhi</i> Zi, Li & Jacobus, <b>sp. nov.</b> and <i>Cincticostella yushui</i> Zi, Li & Jacobus, <b>sp. nov.</b> The egg and winged stages of <i>C. wangi</i> and <i>C. funki</i> are described for the first time. Eggs of all four species have macroreliefs generally similar to one another and to other species in the genus. Male imagoes have preliminary species-level differences in the median convex lobes of the styliger plate and the shapes of the penis lobes themselves. The current delimitation of four complexes of <i>Cincticostella</i> is briefly discussed based on the nymph and winged stages. A partial phylogenetic reconstruction of <i>Cincticostella</i> based on the COI gene illustrates relations of representatives of the four complexes on the one hand and distinct delimitation of <i>C. wangi</i>, <i>C. funki</i>, <i>C. xiazhi</i>, <b>sp. nov.</b>, and <i>C. yushui</i>, <b>sp. nov.</b> on the other. An updated list of species of <i>Cincticostella</i> is provided, along with a new key for the identification of nymphs of the <i>C. nigra</i> complex, which are distinguished primarily based on features of the abdominal terga, mesothoracic projections, tarsal claws, labrum emargination, setation of femora, and body color.