Pitfall traps are widely used in terrestrial ecology to capture ground-dwelling arthropods. In order to determine the effect of covers placed over pitfall traps on their efficiency at capturing of spiders, carabid beetles and ants, four types of pitfall trap were sunk into the ground at dry grassland sites: three pitfall traps were not covered, three were covered with white, three with green and three with black plastic covers. The total catch was 9,364 spiders, 4,352 carabid beetles and 4,157 ants. The distribution of species of spiders and carabid beetles, and the total catch of spiders, carabid beetles and ants did not differ significantly among the four types of trap. Therefore, covers do not appear to affect the capture efficiency of pitfall traps.
Pitfall trapping is one of the most commonly used methods of sampling ground-dwelling arthropods. There are many studies on the effect of design of pitfall traps on their capture efficiency but, so far, none on the influence of the colour of the pitfall trap. In this study the abundances of seven invertebrate groups (Apidae, Araneae, Carabidae, Diptera, Formicidae, Isopoda, Vespinae) caught in pitfall traps of different colours (white, yellow, green, brown) at a dense and dry grassland site in Northwestern Germany were determined. White and yellow pitfall traps caught by far the highest numbers of individuals of Apidae, Araneae, Carabidae, Diptera and Formicidae. Isopoda were most abundant in the catches of green and brown traps. Differences among numbers caught were significant for Apidae, Araneae, Carabidae and Diptera. The effect of colour on the catches did not differ significantly between sites. Knowledge of the variation in the catching efficiency of differently coloured pitfall traps is important for designing invertebrate surveys, both from a scientific and ethical point of view.