1. School of Biosciences, University of BirminghamEdgbaston, Birmingham B15 2TT, UK
2. Laboratory of Entomology, Wageningen UniversityPO Box 8031, 6700 EH Wageningen, The Netherlands
3. Agroscope FAL, Swiss Federal Research Station for Agroecology and AgricultureReckenholzstrasse 191, 8046 Zurich, Switzerland