POPULATION-MOVEMENTS OF ARTHROPODS BETWEEN NATURAL AND CULTIVATED AREAS

'Edge permeability' between habitat patches in a mosaic landscape of mixed intense agriculture and semi-natural areas was investigated with directional trap devices along field borders and in a 300-m long transect through crap fields, pasture, wetland and a dry meadow. Almost all identified arthropod species performaned population exchanges over the field borders. Species abundances clearly depend on habitat quality rather than area or distance to related habitat islands. Most insect species collected in sticky traps over crop fields were never or rarely encountered in the vegetation layer. Surface-dwelling flightless species showed gradual transitions over the field borders. 'Hard edge'-species tended to be specialists for undisturbed perennial habitats, while 'soft-edge'-species with a diffuse distribution were mainly associated with annual crops. It is concluded that in cultivated areas a mosaic landscape of small-sized crop fields and semi-natural habitats maximizes arthropod diversity and decreases the probability for overall extinction even of rare species. © 1990.