Bombus (Sibiricobombus) sibiricus

1. Bombus (Sibiricobombus) sibiricus (Fabricius, 1781) Figs 1, 7–8, 12‒17, 90, 101 Apis ʃibirica [= sibirica] Fabricius, 1781: 478. BOMBUS MELINOIDES Fischer de Waldheim, 1843: pl. 122 n. 1. Bombus flaviventris Friese, 1905: 514. Bombus (Subterraneobombus) flaviventris subsp. ochrobasis Richards, 1930: 655. Bombus (Pyrobombus) nikiforuki Tkalců, 1961: 354. Diagnosis Females Queens body length 20‒21 mm, workers 12‒14 mm. Colour pattern of the hair with the head predominantly black, the thoracic dorsum anterior and posterior bands and metasomal T1‒3 entirely yellow, and hair of the band between the wing bases either yellow or orange or black, and hair of T4‒5 either orange or black, the lower side of thorax and legs black (Figs 12‒14). Morphology with hind basitarsus outer surface in the centre with short branched hairs dense, black and strongly overlapping so that reflections from the outer surface are interrupted; (in large individuals) T6 subapically medially with a longitudinal ridge with a flattened crest. Males Body length 14‒17 mm. Colour pattern of the hair similar to the female, with the head black but with yellow on the vertex and on the clypeus, the thoracic dorsum anterior and posterior bands and metasomal T1‒3 entirely yellow, and hair of the band between the wing bases either yellow or orange or black, and hair of T4‒6 either orange or black, the coxae and legs predominantly black (Figs 15‒17). Morphology with the eye scarcely enlarged relative to the eye of a female bumblebee, from the dorsal aspect the eye separated from the lateral ocellus by more than 2 × the ocellar breadth; S6 with the posterior margin in the middle with a deep concave indentation; penis-valve head with the recurved section broad, narrowing gradually towards the tip (Fig. 90). Type material Lectotype of Apis sibirica (designated here) RUSSIA • ♀ (worker); “Sibiria”; P. Pallas leg.; NHMUK Banks Collection (examined PW). Holotype of Bombus melinoides (by monotypy?) RUSSIA • ♀ (queen); Irkutsk; (type not seen but identity not in doubt). Syntypes of Bombus flaviventris CHINA • 2 ♀♀ (queen, worker); ZMB (examined PW). Holotype of Bombus (Subterraneobombus) flaviventris subsp. ochrobasis (by original designation) CHINA • ♀ (queen); [not] Sikkim [Xizang], “Khamba Jong” [Gampa Dzong]; 15-30 Jul. 1903; NHMUK (examined PW). Holotype of Bombus (Pyrobombus) nikiforuki (by original designation) CHINA • ♀ (worker); Qinghai, “Hsi-li-gou” north of Dulan; 31 Aug. 1950; C. Yang leg.; LMOB (examined PW). Material examined CHINA ‒ Gansu • 2 ♂♂; Yongden, Tongyuan; 36.6767° N, 103.0472° E; 2 Sep. 2010; P. Williams leg.; BOLD nos: 6880C09, 6880C10 (COI); PW, SB058, SB059. ‒ Inner Mongolia • 1 ♀ (worker), 1 ♂; Majiazi; 43.2176° N, 117.3153° E; 10 Sep. 2007; P. Williams leg.; BOLD nos: 6880C11, 6880C12 (COI); PW, SB060, SB061. – Qinghai • 1 ♀ (worker); Xingfucan; 35.8993° N, 97.8892° E; 10 Aug. 2013; P. Williams leg.; PW, SB002 / NHMC06 • 1 ♀ (worker); NW of Dulan; 36.6689° N, 98.1181° E; 14 Aug. 2013; P. Williams leg.; PW, SB001 / NHMC07. ‒ MONGOLIA ‒ Zavkhan • 1 ♀ (worker); Tegshiin Gol; 48.3313° N, 97.8645° E; 22 Jul. 2004; J. Gelhaus leg.; BOLD no.: 1550G03 (COI); KSEM, SB044. Distribution Asian desert-edge and Tibetan Plateau species: Fig. 101 ‒ North Asia: KAZAKHSTAN, MONGOLIA, RUSSIA: East Siberia. ‒ East Asia: CHINA: Xinjiang, Xizang, Qinghai, Gansu, Ningxia, Shaanxi, Hebei, Inner Mongolia. One of the highest recorded bumblebee species in the world at 5640 m a.s.l., along with B. tibeticus Williams, 2020 (recorded in 2018 under the name B. keriensis Morawitz s. lat.) and B. tanguticus Morawitz, 1887 from a site beside the West Rongbuk Glacier in Tibet [= Xizang], at 28.061160° N, 86.847273° E (Williams 2018). The species is so far unrecorded from central Xizang, e.g., in collections from the Tanggu La mountains. (AB, EA, EB, IAR, IZCAS, LMOB, NHMUK, PW, RDJ, UUH, VLA, ZIN, ZMB.) Behaviour Because the male eye is scarcely enlarged relative to the eye of a female, as in most bumblebees, the male mate-searching behaviour is expected to be similar to the most widespread male “patrolling” behaviour (Awram 1970; Svensson 1979), as for B. tunicatus Smith, 1852, compared with “racing” behaviour (below) (Williams 1991). It is also possible, but unrecorded, that the males might seek out colonies with young females. Taxonomic remarks Note on the lectotype of Apis sibirica Fabricius, 1781: this would appear to be (one of?) the specimen(s) referred to by Fabricius (1781) in the original description as being in the Banks Collection (“ Dr. Pallas. Muʃ. Dom. Banks. ”). Because the number of specimens of Apis sibirica in this collection seen by Fabricius was not explicit in the original description and others may have existed, this individual which lacks the left hind tarsi and has some glue on the underside (with a later red-edged, round NHMUK label printed with “Type / H.T.”, a recent printed label identifying B. sibiricus: “BMNH(E) #668744”, and an old drawer label “ Apis Sibirica / Fabr. Sp. ruf.[?] No 22.”) is designated as lectotype in order to reduce uncertainty in the identity of the taxon and in the application of the name. The taxon concept of the species B. sibiricus here agrees with the recent interpretation (Williams 1998), presenting evidence that: (1) our PTP analysis supports independent species-level coalescents in the COI gene (Fig. 1); corroborated by (2) diagnostic morphological character states (see the keys). The species-level coalescent in the COI gene (Fig. 1) also supports as conspecific the red-tailed taxon sibiricus s. str. from Mongolia and the black-tailed taxon flaviventris from the QTP. This conspecificity is corroborated by their closely similar morphology (see the key). Surprisingly, the black-tailed taxon flaviventris has had unusually widely different interpretations by previous authors: (1) as part of a “Gruppe confusus ” (Friese 1905); (2) as part of the subgenus Subterraneobombus (Richards 1930); or (3) as part of the subgenus Sibiricobombus (Williams 1991, 1998). Individuals of the orange-tailed colour pattern vary from having a distinct orange band in the hair between the wing bases (taxon sibiricus s. str.) to having the thoracic dorsum entirely yellow (taxon melinoides).