Sampling epigeal arthropods: an evaluation of fenced pitfall traps using mark-release-recapture and comparisons to unfenced pitfall traps in arable crops

The efficiency of fenced pitfall traps for estimating the density of common ly occurring epigeal predatory beetles was examined using mark-release-reca pture. Most beetles of those recovered were recaptured within one week of t heir release. For seven of the ten species tested recapture rates were over 70%, with higher rates for the larger species. The predatory arthropod spe cies composition captured using fenced pitfall traps was compared to unfenc ed pitfall traps in winter wheat, spring barley and winter oilseed rape. Co mpositional analysis revealed that the dominance structure of seven carabid beetle (Coleoptera: Carabidae) taxa differed between the trap types and mo nth of sampling in winter wheat and spring barley, but differences were sma ll with the exception of a few taxa. Linear relationships between the two t echniques were found for some carabid and rove beetles (Coleoptera: Staphyl inidae). The dominance structure of seven linyphiid spider (Araneae: Linyph iidae) taxa differed between the two trap types in wheat but not barley, al though large differences were restricted to two taxa. No linear relationshi ps between the two techniques were found for any of the Linyphiidae examine d. Rove beetles were more effectively sampled using the fenced compared to unfenced pitfall traps.