(Figs. 1-8)
Material examined. Holotype ♂ and 3 ♂ paratypes from China, Sichuan Province, Pitiao River, Welong, Balangshan Pass, 2700-4000 m, 1-4 June 1991, B. Horvat & I. Sivec (PMSL, 1 paratype-BPS).
Adult habitus. General color pale yellow in alcohol but with a distinctive, narrowly divided, median, pronotal band (Fig. 1) and obscure interocellar brown spot; meso and metathoracic notae with dark brown U-patterns, and abdomen bearing a continuous brown longitudinal band on segments 1-8; tergum 9 with a small, basal dumbbell shaped brown spot. Wings transparent, legs pale.
Male. Forewing length 9.5 mm. Tergum 9 without transverse process and without median excavation on posterior margin (Figs. 5-6). Epiproct about 2.5 X longer than basal width, rod-like but with lateral margins slightly constricted from near base to apical third. Epiproct length ca. 343 µm, subapical width ca. 129 µm, basal width ca. 138 µm, width at narrowest point ca. 71 µm. Epiproct apex a smooth, sclerotized cap but most of dorsal and ventral surface covered with golden brown, closely appressed setae (Figs. 2- 4, 5-8); base with dorsal and lateral bare areas (Figs. 6-7). Epiproct apex slightly inflated in lateral aspect (Figs. 4, 7).
Female. Unknown.
Larva. Unknown.
Etymology. We dedicate this species to the late Professor Dr. C.F. Wu in recognition of his enormous contribution to the knowledge of Chinese Plecoptera.
Diagnosis. This species is similar in pronotal pigment pattern to Sweltsa insularis (Zhiltzova & Levanidova 1978), S. nikkoensis (Okamoto) (Ham 2008), and also to the Japanese species S. abdominalis (Okamoto) and S. sapporoensis (Okamoto), however the general shape and setal pattern of the epiproct is different among these species [except S. sapporensis (Figs. 22-24) and S. nikkoensis (Figs. 25-27) which are quite similar]. Sweltsa wui is the only known Asian species in which the epiproct apex is as wide as, or wider than, the base (Figs. 5-6).
The species of genus Sweltsa are quite variable in epiproct structure and several species complexes in the group may at some time be given generic rank. The structure of tergum 9 in S. wui suggests it could be placed in another genus. A few, unrelated Nearctic species are also known to lack the transverse process (Kondratieff & Baumann 2009), but these species have the posterior margin of tergum 9 strongly concave as in other Nearctic members of the genus. Our study of Asian Sweltsa indicates two Japanese species, S. abdominalis (Figs. 19-21) and S. sapporoensis (Figs. 22-24) share the tergum 9 modifications with Nearctic members of the group but also share a similar color pattern with S. wui. In addition, S. insularis, a similarly pigmented Russian species, also lacks the tergal 9 modification (Figs. 28- 30), but S. colorata (= S. nikkoensis), another Russian species with similar pigment, has a well developed process on tergum 9 (Figs. 25-27). Consequently, in the absence of data from other life stages, we are tentatively placing the new species in genus Sweltsa.