Pitfall trap
A pitfall trap is a trapping pit for small animals, such as insects, amphibians and reptiles. Pitfall traps are mainly used for ecology studies and ecologic pest control. Animals that enter a pitfall trap are unable to escape. This is a form of passive collection, as opposed to active collection where the collector catches each animal (by hand or with a device such as a butterfly net). Active collection may be difficult or time consuming, especially in habitats where it is hard to see the animals such as thick grass.
Structure and composition
Pitfall traps come in a variety of sizes and designs. They come in 2 main forms: dry and wet pitfall traps. Dry pitfall traps consist of a container (tin, jar or drum) buried in the ground with its rim at surface level used to trap mobile animals that fall into it. Wet pitfall traps are basically the same, but contain a solution designed to kill and preserve the trapped animals. The fluids that can be used in these traps include formalin (10% formaldehyde), methylated spirits, alcohol, ethylene glycol, trisodium phosphate, picric acid or even (with daily checked traps) plain water. A little detergent is usually added to break the surface tension of the liquid to promote quick drowning.
The opening is usually covered by a sloped stone or lid or some other object. This is done to reduce the amount of rain and debris entering the trap, and to prevent animals in dry traps from drowning (when it rains) or overheating (during the day) as well as to keep out predators.
