Nepenthes, popularly known as tropical pitcher plants or monkey cups, are a genus of carnivorous plants in the monotypic family Nepenthaceae. The genus comprises roughly 140 species, numerous natural and many cultivated hybrids. They are mostly liana-forming plants of the Old World tropics, ranging from South China, Indonesia, Malaysia and the Philippines; westward to Madagascar (2 species) and the Seychelles; southward to Australia and New Caledonia; and northward to India and Sri Lanka. The greatest diversity occurs on Borneo and Sumatra with many endemic species. Many are plants of hot humid lowland areas, but the majority are tropical montane plants, receiving warm days but cool to cold humid nights year round. A few are considered tropical alpine with cool days and nights near freezing. The name monkey cups refers to the fact that monkeys have been observed drinking rainwater from these plants.