Pitcher plants are a type of carnivorous plant that trap their prey in a cavity filled with a liquid. These traps are sometimes referred to as pitfall traps.
Flies and insects are attracted to the pitcher plants either because of the bright pigments that some of them have, because of a scent some pitchers release into the air, or because of the promise/bribe of sweet nectar.
Once they enter the inside of the pitcher, the creature cannot crawl back out again because the walls are too slippery, or because there may be a barrier mechanism such as downward pointing cilia, or because the pitcher walls may have a backward curve which the insects cannot traverse.
Once trapped, the insects eventually tire, fall into the water and drown, and are then dissolved by enzymes secreted by the pitcher itself. It is from here that the plants get the mineral nutrition they require to survive.
Tricky monkeys!
