Comparison of pitfall traps and litter bags for sampling ground‐dwelling arthropods

Abstract

For their simplicity and effectiveness, pitfall traps have become a standard technique to measure the activity and relative abundance of ground-dwelling arthropods. Permeable screen or mesh bags filled with plant material, referred to as litter bags, have also recently been employed as a complementary sampling technique for epigeal taxa. The anticipated need for increased field research on arthropod populations, particularly in transgenic crops with insecticidal properties, suggests that a relative assessment of both sampling methods could contribute to the design of future studies. Comparisons among pitfall traps, and litter bags placed aboveor below-ground indicated that aboveground litter bags most frequently succeeded in collecting certain groups of arthropods associated with moisture and sheltered areas, including centipedes (Chilopoda) and beetle larvae (Carabidae, Staphylinidae). Conversely, pitfall traps most often captured taxa considered active at ground level, such as adult carabids or harvestmen (Opiliones). For taxa collected in >40% of all three trap types, bootstrap confidence intervals for the coefficient of variation (CV; used to assess precision or sampling efficiency) showed that above-ground litter bags were significantly more precise than pitfall traps for sampling elongate springtails (Collembola) and adult rove beetles (Staphylinidae), but only during the first year of sampling. While below-ground litter bags often appeared similar to one or both of the other trap types, in no case were below-ground litter bags best based on frequency of collection or CV. Though differences were not always consistent between years, results suggest that the additional effort required to sample using litter bags may be justified for the collection of some ground-dwelling taxa. The anticipated need for increased field research on arthropod populations, particularly in transgenic crops with insecticidal properties, suggests that a relative assessment of both sampling methods could contribute to the design of future studies. Comparisons among pitfall traps, and litter bags placed above-or below-ground indicated that aboveground litter bags most frequently succeeded in collecting certain groups of arthropods associated with moisture and sheltered areas, including centipedes (Chilopoda) and beetle larvae (Carabidae, Staphylinidae). Conversely, pitfall traps most often captured taxa considered active at ground level, such as adult carabids or harvestmen (Opiliones). For taxa collected in >40% of all three trap types, bootstrap confidence intervals for the coefficient of variation (CV; used to assess precision or sampling efficiency) showed that above-ground litter bags were significantly more precise than pitfall traps for sampling elongate springtails (Collembola) and adult rove beetles (Staphylinidae), but only during the first year of sampling. While below-ground litter bags often appeared similar to one or both of the other trap types, in no case were below-ground litter bags best based on frequency o...

Different collecting methods reveal different ecological groups of centipedes (Chilopoda)

“…However, our knowledge about the efficiency of different methods is limited. No important differences have been found among some methods (SMITH et al 2008) and no significant differences have been detected between the efficiency of pitfall traps and litter sifting (PRASIFKA et al 2007). This study aimed to find the best combination of methods to ascertain the centiped species' spectrum in Central European forests.…”

Hay-bait traps are a useful tool for sampling of soil dwelling millipedes and centipedes

“…A similar result was found by Ožanová (2001) using grass traps (a small heap of mowed grass on the surface of meadow), with a much higher number of species after 7 weeks than for a shorter exposure time. Although Prasifka et al (2007) did not evaluate the effect of length of exposure time of bait traps, it is evident from their results that below-ground traps were more effective after 8 weeks than after 6 weeks. It supports our results that the best length of exposure of bait traps is from 8 to 10 weeks, although we aware of difficulties with this generalization.…”

“…Wiegert 1974). Prasifka et al (2007) used litter bags to sample ground dwelling invertebrates; they installed litter bags at the soil surface as well as below the soil surface in a corn field. Above-ground bait traps were attractive for centipedes (millipedes were not recorded in this research).…”

Laboratory studies on larval food habits of two syntopic, related, granivorous ground beetles Amara chalcites and A. congrua (Coleoptera: Carabidae): a comparison with stable isotope analysis

“…To address these issues, microscopic and/or chemical analyses of gut contents of field-collected larvae (e.g., Luff 1974;Symondson 2002) and comparisons between the isotope ratios of teneral adults and those of field-collected larvae/ pupae would be particularly informative, although, importantly, such approaches are impractical due to the lack of a species-level identification system for larvae/ pupae of the two species and the difficulty of collecting a sufficient number of larvae/pupae in the field (Lövei and Sunderland 1996). In the future, a DNA-based identification system (Hebert et al 2003) and novel techniques for collecting geophilus larvae (e.g., Brandmayr et al 2007;Prasifka et al 2007) may overcome these problems.…”