Moreover, guidance barrier pitfall traps are not commonly used in applied research (but see Hossain et al. However, only few studies investigated the actual effect of guidance barriers on pitfall trap catches and these studies suffered from low sample sizes and unbalanced sampling efforts with a different number of pitfall traps used in the studied pitfall trap designs ( Hansen & New, 2005 Winder et al., 2001). The use of guidance barriers is meant to increase capture efficiency and the number of singletons which are particularly important in conservation studies where complete biodiversity inventories are desired ( Hansen & New, 2005). To overcome this limitation without increasing the sampling effort and workload, guidance barrier pitfall traps have been introduced. In a conventional simple pitfall trap as proposed by the pioneers Dahl (1896), Barber (1931) and Greenslade (1964) which is basically a container sunk in the soil, a large proportion of ground dwelling beetle species occurring in a habitat will not be detected with sufficient certainty as they are comparatively rare in assemblages ( Driscoll, 2010).

However, the authors did not consider additions to pitfall trap designs such as extended rim plates or guidance barriers although these have been used in previous studies. A recent meta-analysis by Brown & Matthews (2016) discussed many pitfall trap parameters (diameter, depth, colour, rain covers, preservatives and the use of funnels) and even proposed a standardized trap design. Although the limitations of pitfall traps in respect to trait filtering and reflecting diversity and abundances in a habitat appropriately have been intensively discussed, the method is still the best standardized and comparable approach to study ground dwelling arthropods and due to comparative low handling time allows for sufficient replication ( Driscoll, 2010 Kotze et al., 2011).ĭifferent features of pitfall trap designs have undergone review and research over the last decades in order to improve and standardize trap designs: colour of traps ( Buchholz et al., 2010), the presence and colour of rain covers ( Buchholz & Hannig, 2009 Csázár et al., 2018), sampling intervals ( Schirmel et al., 2010), spatial distribution ( Ward, New & Yen, 2001), different preservatives ( Schmidt et al., 2006 Skvarla, Larson & Dowling, 2014) as well as pitfall trap diameters and the use of funnels ( Csázár et al., 2018 Lange, Gossner & Weisser, 2011). Proposed nearly a century ago, pitfall traps remain one of the most commonly applied sampling methods in ecological field studies and are widely used for the assessment of ground dwelling arthropod taxa which are of high importance in modern ecosystem functioning research ( Brown & Matthews, 2016).

Najarala pitfall trap