'Beetle banks' as refuges for beneficial arthropods in farmland: Long-term changes in predator communities and habitat

1 Significant differences in the overwintering densities of predatory carabid and staphylinid beetles and spiders occurred on an 'island' grassy bank habitat composed of blocks of Agrostis stolonifera, Dactylis glomerata, Holcus lanatus and Lolium perenne, within and between winters during a 7-year study. 2 Densities of the predators over the last three winters of the study were greater in the bank than in the boundary of the field in which the bank was situated. 3 Succession occurred in plots of L. perenne, with D. glomerata fully replacing this species. Plots of D. glomerata and H. lanatus remained virtually monospecific. 4 Over the period of study, the beetle bank maintained its role in providing overwintering habitat for polyphagous predators and carabid diversity has increased since the bank was first established. Beetle banks were therefore shown to contribute to conservation biodiversity in an agroecosystem.