Rheocricotopus (P.) bifasciatus Wang & Zheng, 1991 Fig. 2, Table 2 Rheocricotopus bifasciatus Wang & Zheng, 1991: 100. Rheocricotopus (Psilocricotopus) brochus Liu, Lin & Wang, 2014a: 20. Syn. nov. Rheocricotopus (Psilocricotopus) bifasciatus – Saether et al. 2000: 160. — Liu et al. 2014a: 18. — Ashe & O’Connor 2012: 560. Type material Holotype of Rheocricotopus bifasciatus CHINA – Sichuan • ♂; Mt Jinfo; 29.0° N, 107.1° E; 1800 m a.s.l.; 9 May 1986; X. Wang and L. Zheng leg.; NKU. Paratype of Rheocricotopus (P.) brochus CHINA – Zhejiang • ♂; Yueqing, Lingdi, Jiulong; 28°31’ N, 120°96’ E; 18 Apr. 2011; X.L. Lin leg.; NKU. Photographs of the holotype of R. bifasciatus and a paratype of R. (P.) brochus provided by X. Lin (SHOU) were examined. Other material examined CHINA – Guangdong • 1 ♂; Xinyi, Mt Yunkai NNR; 22°16′ N, 111°11′ E; 1130 m a.s.l.; 20 Feb. 2020; S.X. Luo leg.; JNU • 4 ♂♂; same data as for preceding; 20 Apr. 2020. – Anhui • 1 ♂; Huangshan, Tangkou, Mt Huang, Fu stream; 30°05′ N, 118°08′ E; 570 m a.s.l.; 26 May 2012; H.Q. Tang leg.; JNU. Description Male (n = 6) Total length 1.9–2.5, 2.2 mm. COLOURATION. Head dark brown on vertex. Thorax mostly dark brown, with pale HP and pleural membrane; and indistinct scutal vittae. Abdomen (Fig. 2A–B) bicoloured; T I–II, IV entirely yellow; T III entirely brown, or yellow with posteromedial brown marking; remaining tergites dark brown. P 1 (Fig. 2C) largely brown to dark brown with basal tip of fe, apical ⅔– 4 / 5 of ti, and all of ta 1–3 whitish; occasionally ta 2–5 brown. P 2–3 (Fig. 2D) brown to dark brown, with basal tip of fe, apical ⅓–⅔ of ti and all of ta 1–4 whitish; occasionally ta 2–5 brown. HEAD. Temporals 4–8, 6 (5). Antennae broken off. Clypeus trapezoid with 8–10, 9 setae. Lengths (μm) of Pm 1–5: 30–37, 34; 49–57, 52; 98–123, 114; 118–135, 127 (5); 209–258, 233 (3), respectively. Pm 4 / Pm 3 1.0–1.2, 1.1 (5); Pm 5 /Pm 4 1.7–2.0, 1.9 (3). Pm 3 with 5–7, 6 (3) SCl in 2 groups; Pm 4 without SCl. THORAX. Lateral Aps 1–4, 3 (4). Ac 10–16,13 (4); minute, longest 10–12, 10 (4) μm long; Dc 5–7, 6, including 1–2, 2 H, uniserial; Pa 3; Scts 4–7, 5. HP (Fig. 2E) oval, moderately large. WING (Fig. 2F). Length 1.4–1.7, 1.6 mm. C extension moderately long, 62–76, 67 μm. VR 1.0–1.1, 1.1 (5). R with 4–8, 6 setae; R 1 and R 4+5 bare. AnL much reduced. Sq with 1–3, 2 setae. LEGS. P 1 with ti spur 39–42, 41 (5) μm long; P 2 with 2 ti spurs both 15–17, 16 and 15 (5) μm long; P 3 with 2 ti spurs 34–44, 40 (5) and 15–17, 17 (5) μm long. P 2 without Sch. P 3 with ti comb consisting of 10–12, 11 (5) bristles. Lengths and proportions of legs as in Table 2. ABDOMEN (Fig. 2G). Tergal setae irregularly arranged. Hypopygium (Fig. 2H) with AnP sharply pointed at apex, bearing 6–8, 7 (5) lateral setae. Gc 153–165, 157 μm long, 3.1–3.5, 3.2 × as long as broad at middle, with SVo (Fig. 2H) plate-like triangular, relatively thick, apically rounded; IVo triangular double-layered, dorsally with blunt apex. Gs (Fig. 1I) 62–69, 66 μm long, with minute, subapical CD. HR 2.3–2.5, 2.4. Female, pupa and larva Unknown. Distribution The species has been known from Oriental and Palaearctic China. Remarks Only males of this species have been reported from Oriental and Palaearctic China. According to the original description (Wang & Zheng 1991: 100 fig. 2), the male possesses the following features: abdomen dark brown with yellow tergites I–II, and IV; humeral pit distinct, ovoid; antennal ratio ca 0.9; wing with a much-reduced anal lobe and a long costal extension; inferior volsella large, sub-rectangular; crista dorsalis small, preapical. Further, according to W. Liu (pers. comm. 2024), the males collected from Sichuan, Hunan, Ningxia and Gansu provinces in China have an antennal ratio of 0.93, 0.80, 0.80–0.87, and 0.86, respectively. The photographs of the holotype taken by X. Lin (pers. comm. 2022) show that the male has bicoloured legs (tibia dark brown apically with a broad white band), and superior volsella roundly protruded from the base of gonocoxite. The newly collected males from Oriental China are consistent with that of this species in the morphological features except the antenna, all of which were all lost in collecting. This collection includes an interesting and broad colour variation as in Fig. 2B. In the original description of R. (P.) brochus Liu, Lin & Wang, 2014 collected from Oriental China, the authors (Liu et al. 2014a: 22) wrote that the male resembles that of R. (P.) bifasciatus Wang & Zheng, 1991. A significant difference between them is colouration on the tergite III, which is largely yellow and medially brown in the former, whereas entirely brown in the latter. However, the photograph of a paratype of R. (P.) brochus taken by X. Lin (pers. comm. 2022) has a brown posteromedial mark on the yellow tergite III, which also occurs in R. (P.) bifasciatus as an individual variation. Rheocricotopus (P.) brochus is a junior synonym of R. (P.) bifasciatus. The male somewhat resembles that of R. (P.) godavarius from Nepal in the abdomen with white tergites I and IV, and the wing with a much-reduced anal lobe and a distinct costal extension, but differs from it in the entirely yellow tergite II, the higher antennal ratio (AR ca 0.9), and the large distinct humeral pit. According to the original description (Lehmann 1969: 361; 372 fig. 14b), in the latter the tergite II is brown, the antennal ratio is 0.3, and the humeral pit is small and indistinct.

Published as part of Niitsuma, Hiromi & Tang, Hongqu, 2026, Taxonomic review of Rheocricotopus Brundin, 1956 (Diptera: Chironomidae: Orthocladiinae) from East Asia, with descriptions of twelve new species, pp. 1-114 in European Journal of Taxonomy 1037 on pages 12-15, DOI: 10.5852/ejt.2026.1037.3157, http://zenodo.org/record/18507203