Structural Features of Field Boundaries Which Influence the Overwintering Densities of Beneficial Arthropod Predators

Abstract

Vegetation cover was manipulated within enclosures on a field boundary in southern England to test experimentally the effect on the overwintering of Tachyporus hypnorum and Demetrias atricapillus populations, species that use grassy boundaries of arable fields as refugia during winter. Winter survival was lowest for beetles enclosed on bare earth and highest for those enclosed on tussocks of Dactylis glomerata. The contrast in structural complexity of the experimental treatments caused a 44%, 43% and 36% variation in the final densities of beetles during three successive winters. The densities of T. hypnorum on adjacent field boundaries were estimated from the composition of their vegetation cover and the survival rates of the beetles on different treatments