hypnorum -complex

Bombus taiwanensis Williams, Sung, Lin & Lu, 2022

Bombus wolongensis Williams, Ren & Xie sp. nov.

Bombus bryorum Richards, 1930 stat. rev.

= fletcheri Richards, 1934

Bombus hypnorum (Linnaeus, 1758)

= calidus Erichson, 1851

Bombus koropokkrus Sakagami & Ishikawa, 1972 stat. rev.

= insularis Sakagami & Ishikawa, 1969, not of Smith (1861)

Bombus hengduanensis Williams, Ren & Xie sp. nov.

Bombus perplexus Cresson, 1863

= hudsonicus Cresson, 1863

Key to species for females of the hypnorum -complex

Future identification of the species of the hypnorum -complex recognised here will be most reliable for specimens when made from COI-barcode data, which are available for comparison of nucleotide differences with the reference data in BOLD. A key using morphological shape, surface sculpturing, and hair-colour-pattern characters follows below, with the most reliable characters placed at the beginning of each couplet. Our results imply that in many cases we should be able to assign most reliably the specimens with locality labels to species on the basis of their collection locality alone. All identifications of species from the key or from the figures should be checked against the species’ diagnoses within the accounts for each species.

Diagrams showing the variation in the colour-patterns of the dorsal hair are presented in Figs 3‒50. These diagrams summarise only the major differences (Williams 2007) rather than the details (e.g., Williams 1991: figs 311‒316). This is a simplification to aid quantitative comparisons and inevitably requires compromises. Colour-pattern variation within species is established with reference to particular individuals identified from COI barcodes.

1. Head with the ocello-ocular area along the inner eye margin with only one row of larger medium punctures; clypeus in the central area with scattered widely-spaced small punctures and the very large punctures spaced by more than three times their own diameter .............................................. 2

– Head with the ocello-ocular area along the inner eye margin with a broad band of scattered larger medium punctures; clypeus in the central area with a longitudinal band of small punctures and with very large punctures, some spaced by just twice their own diameter ............................................... 4

2. Thoracic dorsum with the hair black; midleg and hindleg basitarsi with integument orange-brown (Taiwan) ................................................................. B. taiwanensis Williams, Sung, Lin & Lu, 2022

– Thoracic dorsum with the hair predominantly brown or yellow; midleg and hindleg basitarsi with integument dark brown or black …................................................................................................... 3

3. Thoracic dorsum predominantly brown, in the centre of the scutum without black hair; labral lamella broad and shallowly rounded, almost rectangular (Himalaya) ............... B. bryorum Richards, 1930

– Hair of the thoracic dorsum dull yellow, in the centre of the scutum with a dense central spot of black hair; labral lamella narrow and deeply rounded, almost pointed in the middle (Sichuan, Yunnan) ...................................................................... B. wolongensis Williams, Ren & Xie sp. nov.

4. Head with the ocello-ocular area along the inner eye margin with a broad band of small and medium punctures, in the posterior shining gap opposite the ocelli the small punctures spaced by about their own breadths; T5 posteriorly in the middle, anterior to the smooth posterior margin, with a narrow band of close large punctures extending for less than an eighth of the length of the tergum ........... 5

– Head with the ocello-ocular area along the inner eye margin with a broad band of medium and small punctures, in the posterior shining gap opposite the ocelli the small punctures spaced by much more than their own breadths; T5 posteriorly in the middle, anterior to the smooth posterior margin, with a broad band of close large punctures extending for at least a quarter of the length of the tergum. 6

5. Hair of T4 either the posterior half white or white at least in a continuous band along the posterior margin; labral tubercle on its broad outer lateral and anterior-facing surface in the centre smooth, with large punctures only along the dorsal and lateral edges (Palaearctic) ......... B. hypnorum s. str.

– Hair of T4 either the posterior half black or with only a few white hairs along the posterior margin; labral tubercle on its broad outer lateral and anterior-facing surface in the centre with a few very large punctures scattered throughout (Hengduan, North China) ........................................................ ............................................................................... B. hengduanensis Williams, Ren & Xie sp. nov.

6. Clypeus in the centre with widely scattered large punctures with more numerous small punctures between them; scutum with the hair usually dull yellow (sometimes dull pale brown), T5 hair usually entirely black, but sometimes white or cream posteriorly and occasionally throughout (Nearctic) .. ................................................................................................................. B. perplexus Cresson, 1863

– Clypeus in the centre with widely scattered large punctures with fewer small punctures between them; scutum with the hair orange-brown, T5 hair usually entirely white, but sometimes only along the posterior margin (Japan, Sakhalin) ....................................................... B. koropokkrus stat. rev.

Accounts of the species

Accounts of the seven accepted species of the hypnorum -complex follow below. Square brackets [Bombus xus] are used to indicate transliterations, translations, interpretations and unavailable names outside the species group (sensu ICZN 1999), including selected misspellings, misidentifications, and infrasubspecific names.