A COMPARISON OF D-VAC SUCTION, FENCED AND UNFENCED PITFALL TRAP SAMPLING OF EPIGEAL ARTHROPODS IN AGROECOSYSTEMS

The aim of this study was to compare relative abundance of epigeal art hropods caught with either unfenced pitfall traps, traps within fences or D-Vac suction sampling in arable habitats (two fields and two mead ows). From our results we conclude that shortterm D-Vac suction sampli ng is not appropriate for the three taxa Carabidae, Staphylinidae, and Lycosidae because relatively large and heavy individuals are underest imated. Fenced and unfenced traps yielded different estimates of the r elative abundance of Carabidae and Staphylinidae: unfenced traps overe stimated the percentage of Carabidae present but underestimated the St aphylinidae. The dominance structure of the carabid assemblages at the sampling sites was more similar for the two trapping methods than for the four sites. In arable fields body size seemed to be the main fact or in determining the catch, but in meadows the trapping efficiency wa s possibly influenced by other variables. Additional laboratory experi ments were carried out to observe the influence of behaviour on pitfal l trap efficiency. Species specific behaviour was shown to bias result s even between species of the same genus (Poecilus). We suggest that i n arable habitats, fenced pitfall traps should be used at least in add ition to unfenced traps. The former allow the standardisation of data to a certain area, whereas the latter are needed to sample large speci es and to determine activity patterns.