Genus Nepenthes (Kantong semar, bahasa Inggris: Tropical pitcher plant), yang termasuk dalam familia monotipik, terdiri dari 130 spesies dan belum termasuk hibrida alami maupun buatan. Genus ini merupakan tumbuhan karnivora di kawasan tropis Dunia Lama, kini meliputi negara Indonesia , Republik Rakyat Tiongkok bagian selatan, Indochina, Malaysia, Filipina, Madagaskar bagian barat, Seychelles, Kaledonia Baru, India, Sri Lanka, dan Australia. Habitat dengan spesies terbanyak ialah di pulau Borneo dan Sumatra. 
Semar bag is a very unique plant because it can prey on various nearby insects such as flies, bees, and others. This carnivorous plant is quite rare so it should be cultivated so as not to quickly become extinct.
Semar bag itself can only prey on insects when he was an adult. He will open his pockets to get insects into it. If there is already trapped, then the pouch will be closed immediately to start digesting the insect.