Insect and Arachnids Monitoring Using a Pitfall Trapping Design

In an attempt to establish a methodology for insect and arachnid surveying, we installed some pitfall traps in the ancient woodland on our site. The Pitfall Trap Survey is used to establish spatial distribution patterns in seasonal insect occurrence, to compare relative abundance in different micro-habitats, to study daily activity rhythms, and in community surveys.
The dry pitfall trap strategy was slightly modified. We installed the pitfall traps in 7×7 m grid with 3m spacing between the trapping cans. Plastic cups were used as pitfall traps with two cups going in one trap. the outer cup was used to protect the inner cup and to allow subsequent rapid emptying of the inner cup. A small hole was punched in outer cups to help the rain water drain.  The holes were dug slightly deeper than the pitfall cups. The soil around the rim of inner cup was smoothed to allow insects to fall into the traps easily. The openings of the cups were covered with a slightly raised lid to prevent insects from heat, water and predators. Three visits were planned over two weeks as it was just an example survey.
The survey results showed the presence of different order classification: Coleoptera, Arachnida, Isopoda, Opiliones, Thysanura and Myriapoda.

In the second visit results, there was an effect noticed on the activity of ground arthropod due to the previous cold night. We found less diversity though there were some beautiful beetles and huge spider in the traps with addition of hexapods.

With arrival of Autumn and the accompanying chill, The third visit results showed a change in the species distribution of ground arthropods – shifting from spiders to beetles. But we still got some great variety.

The method proved promising and would be adapted next year in June when we start conducting the insect surveys with proper monitoring and management of pitfall traps.