Virgin queen execution in the stingless bee Melipona beecheii: The sign stimulus for worker attacksStefan Jarau1, Johan W. Van Veen2, Ingrid Aguilar2 and Manfred Ayasse1
1 Institute for Experimental Ecology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
2 Center for Tropical Bee Research (CINAT), National University of Costa Rica, PO Box 475-3000, Heredia, Costa Rica
Received 5 June 2008 – Revised 22 December 2008 – Accepted 21 January 2009 - Published online 8 August 2009
Abstract - Stingless bees produce considerable numbers of virgin queens over the year, most of which are superfluous and get executed by the workers. Nothing is known yet about the sign stimulus that releases the worker attacks. In the present study we investigated the queen execution process in Melipona beecheii and found in both behavioral observations and experiments with caged living virgin queens that workers are not attracted to them from a distance by means of volatile chemicals. Furthermore, worker aggression, which is obvious towards virgin queens that run through the nest excitedly with their abdomen enlarged and the wings beating, was lowered to almost zero when we made the queens “behavior-less” by experimentally killing them. Our results clearly show that the sign stimulus for releasing the execution behavior in Melipona beecheii workers is not a chemical stimulus but the virgin queens' conspicuous behavior, which, we hypothesize, could act as a direct measure of their fitness.
Key words: stingless bee / Melipona beecheii / virgin queen execution / queen behavior / worker attacks
© INRA, DIB-AGIB, EDP Sciences 2009