Limitations to the use of pitfall traps in ecological studies exemplified by a study of spiders in a field of winter wheat.
Araneae were collected using pitfall traps and absolute density sampling over a period of 6 months in a field of winter wheat in the UK. The numerical species composition of the pitfall trap catch was different from the composition of the community as indicated by density sampling. The relationships between pitfall and density catches with time for single species were inconsistent. Sex ratios differed markedly between the pitfall trap catches and those found in the density samples. The possible causes of the failure of pitfall traps to reflect community composition adequately, and the implications for the use of pitfall traps in ecological sampling are discussed.