These traps have a sticky surface so that an insect or small animal encountering them will adhere to the surface. Placement of the trap is important, as is renewing the sticky surface or discarding traps when they are full. Pitfall traps are sometimes used to help detect and monitor crawling pests. A small pan or tin is placed in the soil with its top flush with the soil surface. The pan is filled halfway with beer.
Beer attracts slugs, which fall in and drown.
A similar pit-fall trap has been used to monitor black vine weevil populations in nurseries and home landscapes. Other traps employ such tactics as placing boards or grapefruit skins in gardens to provide hiding places for slugs and insects. Rolled up newspapers can serve as a similar device for catching earwigs. Pans with soapy water can be used for aphid monitoring and as an aid in control. These are often used with visual color lures.