Bombus richardsiellus (Tkalců, 1968) Figs 13, 78–82, 189, 205 Pyrobombus richardsiellus Tkalců, 1968: 42. Our PTP analysis (Fig. 10) of coalescents in the COI gene within the rufofasciatus -group supports nine species including B. richardsiellus, corroborated by differences in morphology (see the Diagnosis). Females show size-dependent dimorphism in the colour pattern of the hair: large queens have metasomal T1–3 black, T4 anteriorly black and posteriorly white, and T5 white; whereas large workers (which are smaller) have T1 with some yellow hair, T2 anteriorly with at least a few yellow hairs, T4 orange-red, and T5 anteriorly orange-red, T5 posteriorly and T6 (in part) white; and small workers have white hairs intermixed on the face and on the side of the thorax, T1–2 predominantly yellow, and T5 almost entirely orange. Males have the thoracic bands and T1–2 yellow, T3 black, and T4–5 orange-red. Diagnosis Females Queens medium-sized body length 20–21 mm, workers 10–15 mm. Can be distinguished in the Hengduan region by their combination of the hair of the thoracic dorsum with white bands, T1 black or yellow, and T5 posteriorly white (cf. B. rufofasciatus, B. prshewalskyi, B. miniatus, B. friseanus, B. pyrosoma). Males Body length 12 mm. Can be distinguished by their combination of the thorax with yellow bands with the hair of T3 almost entirely black and without a yellow posterior fringe (cf. other rufofasciatus -group species). Genitalia (Fig. 189) with the gonostylus much reduced, less than a quarter as long on its outer side as broad, with the distal edge concave, the inner distal corner with a single- or double-pointed projection, the inner proximal corner broad and nearly 90° (cf. B. miniatus, B. eurythorax, B. pyrosoma, B. formosellus); volsella with the inner distal corner produced as a narrow curved hook. The single examined male specimen (NHMUK) is missing its head, but according to Tkalců (1968) this male had eyes unenlarged relative to the female. Material examined Holotype BURMA • ♀ (queen), holotype of Pyrobombus richardsiellus Tkalců, 1968 by original designation; Adung Valley; 8 Jul. 1931; Lord Cranbrook (= J. Gathorne-Hardy) leg.; NHMUK (examined PW). Material sequenced (3 specimens) CHINA • 1 ♀ (worker); Xizang, Nyingchi; 30.0054° N, 95.2936° E; 12 Aug. 2012; NHMUK seq: NHMCT1 (sequence data from Williams 2018); PW: ML2 • 1 ♀ (worker); Xizang, Galonglashan; 29.8266° N, 95.71532° E; 25 Jul. 2018; Z. Ren leg.; KIB seq: GLLSL203007; KIB: ML563 • 1 ♀ (worker); Xizang, Sangjiu; 28.8089° N, 97.6056° E; 31 Aug. 2014; IBK seq: BB09; IOZ: ML581. Global distribution (Hengduan mountain species) East Asia: CHINA: Xizang. – Southeast Asia: BURMA (north). (IAR, IOZ, KIB, NHMUK, PW.) Until recently, the species was known from only five specimens (two queens, two workers, and one male), most from the Adung Valley, Burma, with one queen from Zayul, Xizang (NHMUK, examined PW). Knowledge of this species has increased substantially recently with the collection of a queen and 14 workers from Sanjiu in Xizang in 2014 (IOZ, examined PW) and a collection of 64 workers from Galonglashan in Xizang in 2018 (KIB, examined PW), which brings the total known number of available specimens to 83. From this information, among bumblebee species with continental distributions, this species remains apparently unusually narrowly distributed (Fig. 205). Behaviour Food-plant choice generalist (ZR unpublished).

Published as part of Williams, Paul H., Altanchimeg, Dorjsuren, Byvaltsev, Alexandr, Jonghe, Roland De, Jaffar, Saleem, Japoshvili, George, Kahono, Sih, Liang, Huan, Mei, Maurizio, Monfared, Alireza, Nidup, Tshering, Raina, Rifat, Ren, Zongxin, Thanoosing, Chawatat, Zhao, Yanhui & Orr, Michael C., 2020, Widespread polytypic species or complexes of local species? Revising bumblebees of the subgenus Melanobombus world-wide (Hymenoptera, Apidae, Bombus), pp. 1-120 in European Journal of Taxonomy 719 on pages 60-61, DOI: 10.5852/ejt.2020.719.1107, http://zenodo.org/record/4064324