1. Field Station Fabrikschleichach; University of Würzburg; Rauhenebrach Germany
2. Bavarian State Institute for Viticulture and Horticulture; Bee Research Center; An der Steige 15 97206 Veitshöchheim Germany
3. Wässeri 8; CH-8816 Hirzel Switzerland
4. Department of Animal Ecology I; University of Bayreuth; Bayreuth Germany