1. Department of Terrestrial Ecology; Netherlands Institute of Ecology; Droevendaalsesteeg10 6708 PB Wageningen The Netherlands
2. Laboratory of Entomology; Wageningen University; PO Box 8031 6700 EH Wageningen The Netherlands
3. Laboratory of Agrozoology; Department of Crop Protection; Ghent University; Coupure Links 653 Ghent B-9000 Belgium