Apis arenaria PANZER 1801; Apis frutetorum PANZER 1801; Apis albinella KIRBY 1802; Psithyrus frutetorum var. interruptus LEPELETIER 1832; Bombus obscurus SEIDL 1838Follows P. Williams: http://www.nhm.ac.uk/research-curation/research/projects/bombus/ps.html#rupestris
Until recently this species was known as Psithyrus rupestris but Psithyrus has now been reduced to a subgenus within Bombus. This is a large cuckoo-bee which is a social parasite on the common and widespread red-tailed bumble bee, Bombus lapidarius. Both species are all black with a red tail, but the female parasite has darker wings. Identification keys and general biology are found in Sladen (1912), Free & Butler (1959), Alford (1975) and Prŷs-Jones & Corbet (1991).
Widespread throughout the British Isles, particularly in southern England, this species declined considerably during and after the 1940s but has shown a remarkable resurgence in the past decade. The host is very widespread and appears to be currently increasing its range northward.
The species ranges from southern Fennoscandia south to the northern coast of the Mediterranean and Sicily, and eastwards to Siberia, Mongolia and northern Kazakhstan (Loken, 1984).