This study compared the efficacy of three types of pitfall traps in four forest and two field habitats. Two traps had aprons and one did not. The two apron traps were the same except for a gap between the trap and the plywood-apron, allowing captures from above or below. Traps were placed in a split-plot design and had three replicates of the three trap types per habitat. The traps were emptied each week from May to September. ANOVA's were performed on 12 trapped species separately over habitats, weeks, and the in- teractions between them. The nonapron trap captured over 40% more individuals than either apron trap, though apron traps tended to be more effective in fields for species found in both habitats. Habitat-trap interactions were only significant in two species. Trap-week interactions were significant in four species.
Epstein, Marc E. and Kulman, Herbert M.
"Effects of Aprons on Pitfall Trap Catches of Carabid Beetles in Forests and Fields,"
The Great Lakes Entomologist, vol 17
Available at: https://scholar.valpo.edu/tgle/vol17/iss4/6