Bombus (Sibiricobombus) sulfureus Friese 1905

5. Bombus (Sibiricobombus) sulfureus Friese, 1905 Figs 1, 7–8, 31‒32, 94 Bombus vorticosus subsp. sulfureus Friese, 1905: 521. BOMBUS (SIBIRICOBOMBUS) SULFUREUS var. [= subsp.] AUREOCORBICULARIS Pittioni, 1937: 121. Diagnosis Females Queens body length 16‒19 mm, workers 15 mm. Colour pattern of the hair with the head predominantly black, the thoracic dorsum anterior and posterior bands and metasomal T1‒6 yellow, lower side of thorax and legs black (Fig. 31). Morphology with the clypeus in its centre with scattered large and few small punctures, so that the surface has smooth shining areas; hindleg basitarsus outer surface with short branched hairs so short and sparse that they are not overlapping and the surface is conspicuously brightly shining; (in large individuals) T6 subapically medially slightly but irregularly raised. Males Body length 15 mm. Colour pattern of the hair with the entire body predominantly yellow, except for the thoracic dorsum with black hair between the wing bases (Fig. 32). Morphology with the eye greatly enlarged relative to the eye of a female bumblebee, from the dorsal aspect the eye separated from the lateral ocellus by 1× the ocellar breadth; S6 with the posterior margin in the middle with a deep concave indentation; volsella posterior to the gonostylus greatly broadened and nearly straight, penis-valve head on its inner side ventrally at the base marked by a ridge with a projecting angle, this angle also marked dorsally on a parallel dorsal ridge; penis-valve head recurved section narrowing gradually towards the tip, volsella just beyond gonostylus 3× its breadth between its distal posterior corners (Fig. 94). Type material Type of B. vorticosus subsp. sulfureus “Asia minor”; (type not seen but identity not in doubt). Holotype of Bombus (Sibiricobombus) sulfureus var. [= subsp.] aureocorbicularis (by monotypy) IRAN • (worker); Alborz, “Keredj-Mazanderan”; Brandt leg.; 12 Aug.; (type not seen but identity not in doubt). Material examined IRAN • 1 ♀ (queen); Qazvin, Werk; 38.5488° N, 47.2609° E; 6 Jun. 2007; A. Monfared leg.; PW, SB008 / NHMI027 • 1 ♀ (worker); Qazvin, Bala Rouch; 36.3870° N, 50.6639° E; 19 Aug. 2012; A. Monfared leg.; PW, SB007 /NHMI025. Distribution Rare West Asian montane species ‒ West Asia: TURKEY, IRAN. (AM, NHMUK, PW, UMons.) Behaviour Because the male eye is greatly enlarged relative to the eye of a female bumblebee and the male antenna is strongly elongated, the male mate-searching behaviour is expected to be similar to the “racing” behaviour described for “ B. asiaticus ” (actually B. longiceps stat. rev.) with these morphological characteristics by Williams (1991). Similar “racing” behaviour has been observed in Turkey (Rasmont et al. 2021). Taxonomic remarks The taxon concept of the species B. sulfureus here agrees with the recent interpretation (Williams 1998; Monfared et al. 2007; Rasmont et al. 2021) of a species separate from B. niveatus, 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). This separation of B. sulfureus from B. niveatus is also supported by a difference in CLGS (Rasmont et al. 2005). The colour pattern of this species shows little variation.