Bumblebees belonging to the subgenus Psithyrus are obligate brood parasites of nest-building bumblebees of the genus Bombus. As parasitic Psithyrus females are not able to collect pollen, they are totally dependent on the host colony to rear their offspring. In Europe, there are cuckoo bumblebees like B. vestalis that are specialised in usurping the nests of only a single host species, B. terrestris. However, some species may also parasitize the nests of several other species, which often are closely related to the preferred host. There are indications, that some Psithyrus species may dominate the workers via pheromones similar to those of the host queen. The host – parasite system in bumblebees will provide an opportunity to investigate, whether host queens and parasite females use the same mechanisms to inhibit worker reproduction. In a comparative approach we seek to identify the dominance signals of Psithyrus females and compare them with the signals of the bumblebee queens. The identification of primer pheromones in social insects, both host as well as parasite species will provide the opportunity to manage both beneficial and harmful social species. Since bumblebees are reared for crop pollination, this aspect is especially important also from an applied point of view.

Females of cuckoo bumblebees emerge from hibernation later than their hosts and search for already established nests of host species. There is clear evidence that volatile compounds play an important role in nest location and host nest recognition, and it was shown that females find the host nests by following odour trails laid by host queens and workers while flying in and out the nest. We are interested to identify chemicals involved in host and host nest recognition.

Coworkers: Kirsten Kreuter, Anna Sramkova

Collaborations: Wittko Francke, Robert Twele (both University of Hamburg), Jan Tengö (Öland. Sweden)

Funding: DFG