Bombus festivus Smith, 1861

Figs 12, 38–45, 183

Bombus festivus Smith, 1861: 152 .

Bombus atrocinctus Smith, 1870: 193 .

Bombus terminalis Smith, 1870: 193 .

Bombus melaleucus subsp. discolor Friese, 1905: 514 .

Bombus handel-mazettii Pittioni, 1939a: 260 .

Bombus calidiformis Pittioni, 1939a: 262 .

Bombus festivus has a distinctive morphology and has been placed in a separate subgenus, Festivobombus (Tkalců 1972) or Atrocinctobombus (Skorikov 1933a: name published without description). A close relationship with other species of the subgenus Melanobombus was supported by an analysis of five genes by Cameron et al. (2007) and these subgenera were synonymised by Williams et al. (2008).

Our PTP analysis (Fig. 10) of coalescents in the COI gene within the festivus- group supports a single species B. festivus, corroborated by differences in morphology (see the Diagnosis).

Females show pronounced size-dependent dimorphism in the colour pattern of the hair: large queens have the thoracic dorsum black with a large white patch in the middle (taxon festivus s. str.); whereas workers (which are smaller) and males have the thoracic dorsum extensively orange-brown (taxa atrocinctus and terminalis). That these castes and sexes are conspecific has been confirmed from examining variation within a colony in Nepal (Ito et al. 1984).

Diagnosis

Females

Queens large body length 22–26 mm, workers 12–17 mm. Can be distinguished by the hair of the thoracic dorsum either black with a large central white spot (queen) or extensively brown (worker), the wings dark brown, and both castes have the hind tibia with the distal posterior corner produced as a short spine (cf. B. hypnorum (Linnaeus, 1758), B. abnormis (Tkalců, 1968)) .

Males

Body length 13–16 mm. Can be distinguished by the hair of the thoracic dorsum extensively brown, similarly coloured to the worker. Genitalia (Fig. 183) with the gonostylus relatively undifferentiated, although the proximal inner projection is only weakly projecting towards the body midline and more strongly extending ventrally and distally beneath and parallel to the inner edge of the main body of the gonostylus as a shelf (similar to some Pyrobombus but more distinctly pronounced, cf. B. hypnorum, B. abnormis); volsella with a pronounced inner distal corner forming a narrow hook ( cf. rufipes -group, lapidarius -group, sichelii -group, keriensis -group); penis valve head with the outer flange only weakly expanded (cf. non- festivus -group); eye unenlarged relative to female eye.

Material examined

Lectotype

INDIA • ♀ (queen), lectotype of Bombus festivus Smith, 1861 by designation of Tkalců (1974a); “N.[orth] W.[est]”; NHMUK (examined PW).

Material sequenced (18 specimens)

NEPAL • 1 ♀ (worker); Bheri, Dilikot; 29.029° N, 81.749° E; 28 May 1995; M. Hartmann leg.; BOLD seq: 1551H10; NME: ML198 • 1 ♀ (worker); no data; BOLD seq: 6876H08; PW: ML197 .

BHUTAN • 1 ♀ (queen); Thimphu, Lungtenphu; 27.4574° N, 89.6655° E; 17 Mar. 1996; H. Feijen leg.; BOLD seq: 6880H01; RMNH: ML505 • 1 ♂; Wangli, Pele-La; 27.5498° N, 90.2157° E; 16 Sep. 1994; G. Schulten leg.; BOLD seq: 6880H03; RMNH: ML507 • 1 ♀ (queen); Thimphu, Phajoding Gompa; 27.479° N, 89.595° E; 25 Apr. 2018; J. Smit leg.; RMNH seq: 1092453; RMNH: ML570 • 1 ♀ (queen); same collection data as for preceding; RMNH seq: 1092451; RMNH: ML572 • 1 ♀ (queen); Wangdue Phodrang, Sephu; 27.53° N, 90.245° E; 3 May 2018; J. Smit leg.; RMNH seq: 1092504; RMNH: ML571 .

CHINA – Yunnan Province • 1 ♂; Dali; 25.75° N, 100.1° E; 8 Jul. 1996; C. Hauser leg.; BOLD seq: 1552A01; SMNS: ML181 • 1 ♀ (worker); Lijiang; 27.0020° N, 100.182° E; 13 Jul. 2017; A. Moss leg.; BOLD seq: 1555C09; PW: ML240 • 1 ♂, 1 ♀ (worker); Lijiang; 27.0156° N, 100.1714° E; 23 Jun. 2017; H. Liang leg.; KIB seq: 15; KIB: ML360 • 1 ♂; same collection data as for preceding; 11 Aug. 2016; KIB seq:16; KIB: ML361 • 1 ♂; same collection data as for preceding; 1 Aug. 2016; KIB seq: 17; KIB: ML362 • 1 ♂; same collection data as for preceding; 11 Aug. 2016; KIB seq:18; KIB: ML363 • 1 ♂; same collection data as for preceding; KIB seq: 19; KIB: ML364 • 1 ♂; same collection data as for preceding; 19 Jul. 2017; H. Liang leg.; KIB seq: 20; KIB: ML365 • 1 ♀; Baima Snow Mountain; 28.3373° N, 99.0771°E; 14 Aug. 2019; M. Orr leg.; IOZ seq: 14F5; IOZ: ML583 . – Sichuan Province • 1 ♂; Luojishan; 27.5811° N, 102.4028° E; 11 Aug. 2005; P. Williams leg.; BOLD seq: 1555E06; PW: ML254 • 1 ♀ (worker); same collection data as for preceding; BOLD seq: 1555E07; PW: ML255 .

Global distribution

(Himalayan, Hengduan, and west Chinese mountain species) East Asia: CHINA: Xizang, Gansu, Sichuan, Yunnan, Shaanxi, Chongqing, Hubei, Guizhou, Guangxi. – Himalaya: INDIA: Himachal Pradesh, Uttaranchal, Sikkim, Darjiling Bengal, Arunachal Pradesh; NEPAL, BHUTAN. – Southeast Asia: BURMA, VIETNAM. (AMNH, IAR, INHS, IOZ, KIB, KIZ, NHMUK, NME, NMS, PW, RMNH, SC, SEHU, SMNS, USNM, ZMUM.) The species is widely distributed and often abundant.

Behaviour

A colony of this species has been described from Nepal (Ito et al. 1984). Food-plant generalists (Williams et al. 2009; An et al. 2014). The male mate-searching behaviour is expected to resemble the patrolling of B. keriensis .