1. Department of Agronomy, Food, Natural Resources, Animals and Environment; University of Padova; viale dell'Università 16, 35020 Legnaro (PD) Italy
2. Beneficial Insects Introduction Research Unit; United States Department of Agriculture, Agricultural Research Service; 501 South Chapel Street Newark 19711 DE U.S.A
3. Department of Entomology and Wildlife Ecology; University of Delaware; 250 Townsend Hall, 19716 Newark DE U.S.A