There are two major groups of Pitcher Plants, the North American Family (Sarracenia) and the Tropical Pitcher Plants (Nepenthes).  Both capture insects using the pitfall method.  They lure insects to the rim of the pitcher by a sweet nectar.  Once the insect is attracted to the plant, it begins to drink around the rim and ultimately loses its footing and slips on the sticky walls.  Once inside, escape is slim to none.  The insect is digested by the plant in a bath of digestive enzymes!