Sampling efficiency of pitfall traps and Winkler extractor for inventory of harvestmen (Arachnida: Opilionidae)

Most soil and leaf litter invertebrates lack efficient inventory methods. We evaluated the efficiency of the pitfall traps (or Barber method) and Winkler extractor (or Winkler method) in a beech forest on limestone in southwestern Romania using harvestmen (Arachnida: Opilionidae) as target group. The aim was to test if the relative abundance, species richness and species composition differ between the two methods. The harvestmen relative abundance and species richness were different when assessed by the two sampling methods. Winkler extractor captured greater numbers of harvestmen than pitfall traps, whereas pitfall traps caught more harvestmen species. Harvestmen assemblages as determined by Winkler method were found to be more similar with natural harvestmen assemblages. If the aim of the study is to analyse the community patterns Winkler extractor could be more efficient then pitfall traps. Our study suggests that the choice of the sampling method should be applied depending on the type of the investigation.