Final answer:
Pitfall traps are best used to sample ground-dwelling invertebrates, such as soil-dwelling insects, spiders, and small invertebrates.
Step-by-step explanation:
Pitfall traps are best used to sample ground-dwelling invertebrates. These traps consist of a container sunk into the ground with the opening at ground level. The organism being sampled will fall into the trap as it moves across the ground. This method is commonly used to study soil-dwelling insects, spiders, and other small invertebrates.