Pitfall trap construction affects the efficacy of ground beetle counts

Abstract

Ground beetles were sampled in a broadleaved deciduous forest in Kaluga Province in April–October 1995 using 90 traps grouped in 18 experimental plots. Three types of pitfall traps were used: glass jars, white plastic cups, and cylindrical containers made of transparent plastic bottles. Two types of cover put above the traps were tested: transparent and black. Altogether, 72 carabid species were found, of which only 10 species were shared by all the experimental plots: Leistus terminatus, Carabus hortensis, C. glabratus, Cychrus caraboides, Pterostichus niger, P. oblongopunctatus, P. strenuus, P. melanarius, Calathus micropterus, and Badister lacertosus. The Jaccard binary similarity index between the experimental plots amounted to 37–68% while the Bray-Curtis similarity index was 66–89%. Both the trap type and the cover color significantly affected the similarity of the species structure and species composition of the samples. Plastic cups provided the highest catches of beetles, but this was due to the most abundant species, P. oblongopunctatus. Containers provided the highest catches of C. glabratus. The total abundance was higher for the traps with transparent covers than for those with black covers. Traps with transparent covers provided significantly higher catches of L. terminatus, P. oblongopunctatus, Asaphidion flavipes, and Harpalus rufipes. An adequate assessment of the species composition of a particular habitat requires at least 30 pitfall traps.