Pitfall trap is used for

Pitfall trap is used for Ground beetles, Collembola and Spiders.
Pitfall trap is a simple device used to catch small animals. A hole in the ground into which a bucket or pipe is placed into the soil so that the mouth is level with the soil surface.
These traps are often used to capture small mammals, reptiles and frogs that fall into the pit and cannot escape due to the smooth walls.