Pitcher plant trap, coloured scanning electron micrograph (SEM). Nepenthes pitcher plants are tropical carnivorous plants. The trap (or pitcher) starts as a small bud and gradually expands to form the structure seen here. Scent, nectar and colour attract insects that fall into the liquid at the bottom of the pitcher. Trapped there, they are dissolved by digestive enzymes. This provides the plant with nutrients, such as phosphorous and nitrogen. Pitcher plants are found in nutrient-poor habitats, such as swamps.