1. Department of Population Biology Institute for Biodiversity and Ecosystem Dynamics University of Amsterdam PO Box 94240 1090 GE Amsterdam the Netherlands
2. Department of Entomology University of Viçosa Viçosa Brazil
3. Department of Agricultural Development Laboratory of Agricultural Entomology and Zoology Democritus University of Thrace Pantazidou 193 68 200 Orestiada Greece
4. Department of Plant Physiology Swammerdam Institute for Life Sciences University of Amsterdam PO box 94215 1090 GE Amsterdam the Netherlands