Bombus pyrosoma Morawitz, 1890

Figs 13, 91–97, 191

Bombus pyrosoma Morawitz, 1890: 349 .

Bombus rufus Friese, 1905: 511 (non Villers, 1789: 328 = B. pascuorum (Scopoli)) .

Pyrobombus wutaishanensis Tkalců, 1968: 39 .

Bombus pyrrhosoma – von Dalla Torre 1896: 544, unjustified emendation.

Our PTP analysis (Fig. 10) supports relatively strongly two coalescents in the COI gene for sister species within a pyrosoma -complex: the north Chinese B. pyrosoma s. str. and the Taiwan endemic B. formosellus . The two coalescent groups differ in COI barcode sequences for at least 12 diagnostic nucleotide positions (1.8% of the barcode region). These nucleotide differences are all synonymous, making no difference to the amino acid sequences at translation.

From morphology, B. pyrosoma s. str. has a more extensively black colour pattern than B. formosellus for the females on the thoracic dorsum and T1 (larger workers and queens).

Females show size-dependent dimorphism in the colour pattern of the hair: large queens have the thorax and T1 black and T2–5 orange-red; whereas workers (which are smaller) have the anterior and posterior thoracic bands and T1 white, T2 chocolate brown, and T3–5 orange-red. Males have the anterior and posterior thoracic bands and T1–2 yellow and T3–5 orange-red.

Diagnosis

Females

Queens medium-sized body length 20–23 mm, workers 12–15 mm. Can be distinguished in North China by their combination of the hair of the thoracic dorsum and T1 either black or with white bands with T3–5 red (cf. B. sichelii).

Males

Body length 13–17 mm. Can usually be distinguished in North China by their combination of the hair of the thoracic dorsum with yellow bands, side of the thorax yellow, and T3–7 red. Genitalia (Fig. 191) with the gonostylus much reduced, less than a quarter as long on its outer side as broad, with the distal edge concave and the inner distal corner with two almost equally pronounced adjacent acute teeth (cf. other rufofasciatus -group species with the possible exceptions of B. prshewalskyi, B. friseanus); volsella with the inner distal corner produced as a narrow curved hook ( cf. rufipes -group, B. simillimus, lapidarius -group, sichelii -group, keriensis -group); eye unenlarged relative to female eye.

Material examined

Syntype

CHINA • ♀ (queen), syntype of Bombus pyrosoma Morawitz, 1890 (Williams 1991); “Kan-ssu” (= Gansu); Jun. 1884; G. Potanin leg.; ZIN (examined PW). The specimen bears a label “Schanji / M. Utai”, which could be a corruption of Mt Wutai in the province of Shanxi, where this species does occur (PW pers. obs.).

Material sequenced (10 specimens)

CHINA – Qinghai Province • 1 ♀ (worker); Ping’an; 36.3594° N, 102.1173° E; 19 Aug. 2013; P. Williams leg.; BOLD seq: 1555C04; PW: ML235 . – Gansu Province • 1 ♀ (worker); Xiahe; 35.3644° N, 102.881° E; 27 Aug. 2009; P. Williams leg.; BOLD seq: 1555G08; PW: ML298 • 1 ♀ (worker); Diebu; 34.2401° N, 103.1547° E; 29 Aug. 2009; P. Williams leg.; BOLD seq: 1555G09; PW: ML299 . – Beijing Municipality • 1 ♂; Lingshan; 39.9755° N, 115.4803° E; 20 Apr. 2007; reared from a queen; BOLD seq: 3262E11; PW: ML3 • 1 ♂; same collection data as for preceding; BOLD seq: 3262E12; PW: ML6 • 1 ♀ (queen); Beijing; same collection data as for preceding; BOLD seq: 3263E11; PW: ML211 • 1 ♀ (queen); same collection data as for preceding; BOLD seq: 3263E12; PW: ML212 . – Neimenggu Province • 1 ♀ (worker); Majiazi; 43.2176° N, 117.3153° E; 10 Sep. 2007; P. Williams leg.; BOLD seq: 1555C03; PW: ML234 . – Ningxia Autonomous Region • 1 ♀ (worker); Liupanshan; 35.77438° N, 106.18371° E; 27 Jul. 2018; K. Li leg.; KIB seq: NX03; KIB: ML561 • 1 ♀ (worker); same collection data as for preceding; KIB seq: NX04; KIB: ML562 .

Global distribution

(North Chinese mountain species) East Asia: CHINA: Qinghai, Sichuan, Chongqing, Hubei, Henan, Shandong, Gansu, Neimenggu, Ningxia, Shaanxi, Shanxi, Hebei, Beijing, Tianjin, Liaoning. (IAR, IOZ, NHMUK, PW, ZIN, ZMHB.) The species is widely distributed in North China and often one of the most abundant.

Behaviour

Food-plant generalists (An et al. 2014). Male mate-searching behaviour appears to resemble patrolling of B. eurythorax (PW pers. obs.).