What method involves using a container sunk into the ground for trapping insects?

The method that involves using a container sunk into the ground for trapping insects is known as pitfall trapping. This technique is particularly effective for capturing ground-dwelling insects. By placing a container, typically filled with a preservative or water, into the soil flush with the ground surface, insects that wander into the container are unable to escape and are effectively trapped.

Pitfall traps are commonly used in entomological surveys to monitor insect populations and determine the diversity of species in a given area. This method is relatively easy to use and provides a practical means of assessing insect activity without the need for extensive and complex equipment or sampling techniques.

Other methods such as square-foot sampling and visual inspection involve different approaches to assess insect presence and populations, while the flotation technique typically pertains to separating insects from soil or debris rather than trapping them directly in situ.