1. Department of Entomology, University of Minnesota, St. Paul, Minnesota 55108
2. Department of Entomology, North Dakota State University, Fargo, North Dakota 58105
3. School of Statistics, University of Minnesota, Minneapolis, Minnesota 55455
4. Netherlands Institute of Ecology, 3631 AC Nieuwersluis, The Netherlands
5. Laboratory of Entomology, Wageningen University, 6709 PD Wageningen, The Netherlands and
6. Department of Entomology, University of Illinois, Urbana, Illinois 61801