A pitfall trap for large-scale trapping of Carabidae: Comparison against conventional design, using two different preservatives

A pitfall trap design with an integrated lid was tested against an open-topped (conventional) design for efficiency of trapping Carabidae. Its design benefits include ease of use, integrated rain cover, reduction of small vertebrate entry, and protection against tampering by large vertebrates, making it well suited for use in large-scale invertebrate trapping regimes. Catches of only two of seven common carabid species were significantly affected by trap design: Calathus advena Lec. occurred more frequently (mean = 7.15 vs. 2.10) in a conventional, open-topped trap design and Elaphrus americanus Dej. was captured more frequently by the modified design (mean = 1.45 vs. 0.76). Cluster analysis, based on Bray-Curtis index of percent similarity, showed that on average catches were 70% similar. Catches clustered primarily by trap design (not collection fluid). Trapping efficiency of Carabidae between ethylene glycol and brine did not differ statistically, but specimens were better preserved in ethylene glycol, particularly where solution dilution from rainwater occurred. Gastropods were captured in similar numbers regardless of treatment. Small vertebrates (amphibians) were almost entirely excluded from the modified design (1:13, modified: standard catch). Based on our results, the use of the modified design with glycol-based preservatives is recommended for large-scale trapping for ecological studies.