1. Biologie I, Universität Regensburg, D-93053 Regensburg, Germany;
2. Département d'Écologie et Évolution, Biophore, Université de Lausanne, 1015 Lausanne, Switzerland;
3. Laboratory of Apiculture and Social Insects, School of Life Sciences, University of Sussex, Falmer BN19QG, United Kingdom;