Northern Ireland's Priority Species

Bombus (Psithyrus) rupestris – a cuckoo bumblebee

Bombus (Psithyrus) rupestris

Bombus (Psithyrus) rupestris (Fabricius)
Family: Apidae

Cuckoo or inquiline bumblebees are bumblebees which produce no workers and do not found their own colony. Instead the cuckoo species takes over an active nest of another bumblebee species, in this case the red-tailed bumblebee Bombus lapidarius. The cuckoo female then lays her own eggs and these are tended by the host workers, producing a new generation in late summer.

In brief

  • There have been just three Northern Ireland records, the last in 1989 from Murlough National Nature Reserve, County Down

  • B. rupestris adults can be seen from May to September. The largest numbers are seen in July and August when males and queens of new generation are produced

  • Mated queens of Bombus rupestris overwinter but do not emerge until May, somewhat later than its host

  • It is found along with the host bee, the red-tailed bumblebee Bombus lapidarius, in dry unimproved, grassland, chiefly on the coast

  • This species can only survive where there is a strong population of its host. The host species appears to have declined in Northern Ireland due to loss of its habitat

  • Cuckoo bumblebee queens are not always successful in taking over nests and they may be driven from the nest by the defending workers or even killed

  • The queens of cuckoo bumblebee are heavy-bodied, with thicker cuticles that give them some protection from the stings of the host workers should they attack

  • It is a rare species which has undergone rapid decline.

Species description
The queens are large with a black body with a ‘tail’ of red hairs at the tip of the abdomen. The wings are suffused dark brown. This combination of colours is a unique feature amongst Irish bumblebees. Males are smaller with clear wings and many have some dull yellow hairs on the front of the abdomen and on both the front and rear of the thorax. These yellow hairs, however, do not form a distinct band.

Life cycle
Queens of B. rupestris emerge in late spring and immediately start searching for host nests. They also visit flowers to feed. When a nest of the host is located, the queen of B. rupestris will enter and try and remain undetected by the host workers. She may kill the host queen or simply cohabit with her. There are observations of queens of the host and cuckoo species remaining together in the nest. The cuckoo bee then lays her eggs and the workers of the bumblebee host raise the cuckoo brood. Some accounts say the cuckoo queen dies soon after laying her eggs, others state that she remains alive to defend her eggs and subjugate the host workers. The new generation of males and females emerges in late summer and mates. Males die after mating and the females quickly enter hibernation which will last perhaps nine months to the next spring. Populations of B. rupestris are known to vary considerably in abundance from year to year.

Similar species
Bombus rupestris adults closely resemble the adults of the red-tailed bumblebee Bombus lapidarius, which is the only common red-tailed species in the region. Queens of the red-tailed bumblebee have clear wings and the red tail is brighter red. Males of the host and cuckoo are much more similar in appearance. The male red-tailed bumblebee has distinct bands of bright yellow hairs on the front of the thorax and abdomen and always has yellow hairs on the face between the eyes.

How to see this species
The best chance of seeing this species is on sites with large populations of its bumblebee host. The largest populations of the red-tailed bumblebee are on coastal, flower-rich sites, especially the dunes on the east coast of Down. The red-tailed bumblebee is generally rare away from the coast in Northern Ireland, and inland populations are unlikely to be strong enough to support the cuckoo species. B. rupestris adults can be seen from May to September. The largest numbers are seen in July and August when males and queens of a new generation are produced. Relevant access permissions should always be sought prior to visiting any sites.

Current status
There have been no records since 1989 when it was described as common on the dunes at Murlough. There have been just three Northern Ireland records. It has been recorded in most parts of Ireland, but the post-1980 records are restricted to sites on the south and west coasts.

Why is this species a priority in Northern Ireland?

  • It is rare and has undergone rapid decline in Northern Ireland.

There is evidence of a decline throughout Ireland.

Threats/Causes of decline
As a parasite, the survival of Bombus rupestris is dependent on the presence of a large population of its host. The host species, like many bumblebee species, appears to have declined in Northern Ireland as its habitat has been lost, in particular the loss of extensive areas of flower-rich grassland.

Conservation of this species

Current action

  • Murlough is a National Nature Reserve owned and managed by the National Trust. It is also designated as a SAC and ASSI.

Proposed objectives/actions

  • Survey suitable sites to locate extant populations and, if any are found, ensure the population is maintained.

What you can do
If you see the species, report any sightings to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU, Tel: 028 9039 5256, [at] or to the Bees, Wasps and Ants Recording Scheme (BWARS) who organise the recording of bumblebees in Britain and Ireland.

Further information


The National Trust

Alford, D.V. (1975). Bumblebees. Davis-Poynter, London.

Benton, T. (2006). Bumblebees New Naturalist, Harper Collins.

Edwards, M. and Jenner, M. (2005). Field Guide to the Bumblebees of Great Britain and Ireland. Ocelli.

Pr&375;s-Jones, O.E. and Corbet, S.A. (1991). Bumblebees. Naturalists’ Handbooks 6, Richmond Publishing Co. Ltd.

Text written by:
Dr Brian Nelson, Curator of Freshwater Invertebrates, Ulster Museum