Queens are active from mid April to mid October, workers from early July to mid October, and males from late July to early October. The flight season starts later and finishes earlier in the northern parts of its range (Söderman & Leinonen, 2003).
Parasites: No Bombus seems to usurp the nests of this species, but the mutillid wasp Mutilla europaea, and the fly Brachycoma devia are cited as parasites by Peeters, Raemakers & Smit, (1999).
Taxonomic status: B. bannitus in the broad sense (= B. smithianus of authors, a misidentification (= B. pascuorum)), including B. agricolae for the British forms from the Outer Scottish Isles and Shetland, has been regarded as a separate species by some authors (e.g. Richards, 1935; Tkalcu, 1987; Rasmont & Adamski, 1995) on the basis of its semi-melanic colour pattern and more coarsely sculptured surface of gastral terga IV-V. However, Løken (1973: fig. 81) found no difference between these taxa in a morphometric study (other authors reporting no clear morphological differences include Richards, 1935; Alford, 1975; Pekkarinen, 1979; Rasmont, 1982; Baker, 1996a) and P. Wiliams has collected many specimens with a range of intermediate colour patterns on the Isle of Skye in western Scotland. Until more evidence to the contrary is available from critical studies of patterns of variation, these should be treated as parts of a single variable species.
B. pereziellus has also been regarded as a separate species by Rasmont & Adamski (1995), because of its dark colour pattern (even darker than B. bannitus, B. pereziellus has the thoracic dorsum black rather than red-brown, and has more black hairs on gastral tergum II, whereas these black hairs tend to be more frequent on tergum I for B. bannitus) and because it is endemic to the island of Corsica. Morphologically it was considered by Rasmont (1982) to show no perceptible differences from B. muscorum or B. bannitus. Furthermore, a male with a colour pattern apparently intermediate between B. muscorum and B. pereziellus is mentioned by Delmas (1976:271). Depending on the species concept embraced, some differences might be expected for a peripheral population such as this even if it were conspecific and I shall treat them as parts of a single variable species. Further evidence is awaited.
Nomenclature: The orthography of Linnaeus (1758) employs a long 's' (similar to 'f' or 'f'), a common practice of the period. This convention has since changed and recent authors have consistently used 's'.
Richards (1935, 1968), Yarrow (1968) and Løken (1973) recognised that none of the admissable syntypes in the Linnean collection agreed with the traditional interpretation of B. muscorum, which is very rare in the parts of Sweden where Linnaeus collected (Richards, 1935; Løken, 1973; Day, 1979), but took no action. When Day (1979) came to fix the application of the name, he had no reason to believe that Linnaeus had not described his A. muscorum from the syntype specimen that was subsequently described as lectotype (= B. humilis Illiger).
To reaffirm the traditional usage of B. muscorum, a case was made to ICZN by Løken et al. (1994). This sought an Opinion from ICZN (ICZN, 1996) that set aside by use of its Plenary Power (ICZN, 1985: Articles 78b, 79) the lectotype designation for A. muscorum by Day from application of the Code (ICZN, 1985) and then designated a neotype (ICZN, 1996: 64) to conserve the traditional usage of the name for even the narrowest concept of the taxon (ICZN, 1985: Article 75) (in prep.).