in most plants. The lamina is green, often with a red midrib. Pitchers are yellowish-green. Danser described the colour of herbarium specimens as "blackish in all parts". Ecology Nepenthes inermis is endemic to a number peaks in the Barisan Mountains that line the western side of Sumatra. More specifically, it is known only from the Indonesian provinces of West Sumatra and Jambi. The species has an altitudinal distribution of above sea level. It usually grows as an epiphyte in mossy forest, but also occurs terrestrially in stunted upper montane vegetation above . Substantial populations of this species are present on Mount Talang, Mount Gadut, and Mount Belirang. Nepenthes inermis is particularly abundant on the western slopes of the latter, where it grows terrestrially. It has also been recorded from Mount Gadang in West Sumatra. The conservation status of N. inermis is listed as Least concern on the IUCN Red List. Carnivory Nepenthes inermis produces extremely thick mucilaginous pitcher liquid. It is so viscous that if a pitcher is held upside down, the fluid will pour out, forming an unbroken stream several metres in length. This fluid coats the entire inner surfaces of the pitchers in a thin film. The pitchers of N. inermis function not only as pitfall traps but also as flypaper traps, with the sticky inner walls trapping flying insects above the surface of the fluid. The fluid also acts as a lubricant, allowing prey items to easily slide down into the bottom of the pitcher cup. The upper pitchers of N. inermis are frequently tipped over during downpours. The rainwater that accumulates in them is lost, but the extremely viscous fluid, together with the laterally appressed walls, ensure that the contents is retained. No longer holding heavy rainwater, the pitchers quickly spring back to an upright position. A similar trapping method may be employed by related species such as N. dubia, which also produce very viscous pitcher fluid. Nepenthes inermis pitchers mostly trap flying insects, particularly those of the two fly suborders: Nematocera and Brachycera. However, they do not normally contain invertebrate pitcher infauna. It has been suggested that glands on the lid secrete compounds that intoxicate visiting insects, such that they lose their footing and fall into the pitcher. Related species Nepenthes inermis belongs to a group of closely related montane Sumatran species that includes N. dubia, N. flava, N. jacquelineae, N. jamban, N. talangensis, and