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Due to these complications, density estimation and community assemblage structures portrayed from pitfall trapping are often biased (Mommertz et al. Arthropod species also respond differently to the choice of liquid attractant and detergent, and the arrangement of traps (Schmidt et al. However, trapping efficiency is often sensitive to the population density of a species, its locomotion and olfaction, and the habitat specificity (Perner & Schueler 2004 Niemelä & Kotze 2009 Schirmel et al.
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Pitfall traps have been the standard and most frequently used approach for surveying ground-dwelling arthropods because they are easy to handle and can collect high numbers of individuals and species efficiently (Perner & Schueler 2004 Schmidt et al. 2012) and have important functions in agroecosystems such as controlling pests and maintaining food chain robustness (Landis, Wratten & Gurr 2000 Tscharntke et al.
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Ground-dwelling arthropods are highly diverse and abundant in crop fields and semi-natural habitats across the world (Finke & Snyder 2010 Chaplin-Kramer et al. TCM is a promising technique for the density estimation of ground-dwelling arthropods, especially for traps with liquid attractant and areas with relatively homogenous habitat and away from habitat edges.Pitfall trapping of ground-dwelling arthropods on two habitats (crop field and desert steppe) confirmed this conclusion when comparing estimation from TCM and NCA with densities obtained from the SSM. Simulations with known arthropod densities and effective trapping radius suggested that TCM produced accurate density estimation, while NCA significantly underestimated the known density.We compared the performance of TCM with the estimator based on the nested-cross array (NCA) for arranging pitfall traps, by comparing predicted densities from these two methods with the real density obtained from the suction sampling method (SSM).The density and effective trapping radius can be estimated from a nonlinear regression of the change in the total number of individuals caught with the distance between the paired pitfall traps. Multiple pairs of traps are located different distances apart, and the intersection of trapping areas can be calculated using the inverse trigonometric function. We developed a two-circle method (TCM) for simultaneously estimating densities of ground-dwelling arthropods and the effective trapping radius.Pitfall traps are widely used for investigating ground-dwelling arthropods, but have been heavily criticized due to their species-, habitat- and attractant-specific trapping radius which produces unreliable estimation of species diversity and density.