Nepenthes, popularly known as tropical pitcher plants or monkey cups, is a genus of carnivorous plants in the monotypic family Nepenthaceae. The genus comprises roughly 140 species, and numerous natural and many cultivated hybrids. They are mostly vine-forming plants of the Old World tropics, ranging from South China, Indonesia, Malaysia and the Philippines; westward to Madagascar and the Seychelles; southward to Australia and New Caledonia; and northward to India and Sri Lanka. The greatest diversity occurs on Borneo, Sumatra, and the Philippines. This mix consists of tropical montane plants, receiving warm days but cool to cold, humid nights year-round. The name “monkey cups” refers to the fact that monkeys have been observed drinking rainwater from these plants.

They are commonly grown as curiosity plants and are a source of wonder for children and adults alike. They form pitchers (cups) that hang from trees. Its pitchers are similar to that of the North American pitcher plant, Sarracenia in that it relies on a pool of water to trap its prey. It has a most unusual leaf that first looks like a normal leaf but then develops a tendril at its tip, and finally the tip of the tendril develops an amazing pitcher. It gains support by twining the tendril around another plant. The trap, like Sarracenia species, lures its prey into the pitfall trap by a combination of decaying odours and sometimes a red colouration. As the pitcher develops, it swells and droops due to its weight. As it matures, it suddenly begins inflating with air. Once the pitcher is inflated, it begins to fill with liquid and then opens to reveal the enticing interior. The top of the trap has a lid that initially covers the pitcher until growth is complete. When the leaf is fully grown, the lid opens, and the trap is ready. They attract insects with the odour of nectar. Once inside, the insect finds it cannot get a grip on the walls of the pitcher because a flaky wax on the interior surface peels off as it struggles to climb. Eventually, it falls into the water and struggles to escape. The motion caused by the struggle stimulates digestive glands to release a digestive acid. This acid is so strong that a midge will disappear within hours. The largest of these, the Rajah pitcher, can digest mice! Like Sarracenia species, this one too has its live inhabitants, the largest of which is a small crab. Insect larvae feed on the decaying remains of prey. Others live in the upper levels and dip down occasionally to seize one of the larval inhabitants. In one case, the plant provides a chamber in its stem where ants live. The ants venture to the pitchers, grab some of the decaying prey, and sit on the lip of the pitcher to dismember it. As they break apart the body, pieces fall back into the pitcher’s awaiting pool, where the now smaller fragments decay more quickly than would a whole insect.