Limitations to the Use of Pitfall Traps in Ecological Studies Exemplified by a Study of Spiders in a Field of Winter Wheat

1. Spiders were collected over a period of 6 months by pitfall trapping and absolute density sampling. 2. The numerical species composition of the pitfall trap catch was different to the composition of the spider community as indicated by density sampling. 3. The relationships between pitfall and density catches with time for single species were inconsistent. 4. Sex ratios differed markedly between the pitfall trap catch and those found in the density samples. 5. 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 in the light of recent literature.