Bombus (Psithyrus) barbutellus
Bombus barbutellus has a distribution extending from S.Spain (?) to the South to mid-Finland to the North and from Ireland to the West to Far-East of Russian to the East. It inquilines mainly B. hortorum, B. ruderatus and B. argillaceus but it is much rarer than its hosts. Most data are ancient.
There are two subspecies that have been considered as two separated species by most authors. Lecocq et al. 2011 demonstrated that they are conspecific. The ssp. barbutellus is more abundant in the north of the distribution, while maxillosus occurs mainly in the south.