Creation of "island' habitats in farmland to manipulate populations of beneficial arthropods: predator densities and emigration

Grass-sown raised earth banks were created as "islands' in the centres of two cereal fields to provide improved overwintering conditions for invertebrate predators. During the first year of establishment, the new habitats provided overwintering refuge sites for many species of Araneae, Carabidae and Staphylinidae. Ground-zone searches provided total polyphagous predator densities of up to 150 m^-2. During the second year, grass establishment increased still further and predator numbers exceeded 1500 m^-2 in some grass treatments. Vacuum-net samples taken during the second spring after establishment, showed that the overwintering populations of two predator species in the new habitats influenced dispersal patterns into the crop. -from Authors