national park. Although it appears to be locally abundant, Stewart McPherson considers the species to be "at significant risk of being poached and over-collected" and cites the "rapid demise" of N. aristolochioides, another highly sought-after Sumatran plant, as an example of the possible fate of this species. Carnivory The pitcher fluid of N. flava is highly viscous and coats the inner pitcher walls. This is especially true of aerial traps, which must contend with the action of the wind. The sticky inner walls have been observed to trap small flying insects above the surface of the fluid. The prey subsequently slide down into the fluid where they are digested. It has been suggested that the pitchers of this species function not only as pitfall traps but also as flypaper traps. Indeed, this trapping method is employed by the closely related N. inermis, which also produces highly viscous pitcher fluid. Related species Nepenthes flava is thought to be closely related to both N. inermis and N. jacquelineae. However, it cannot be a natural hybrid between these species as it does not occur sympatrically with them. The pitchers of N. flava bear a close resemblance to those of N. jacquelineae. Nepenthes flava differs from this species in that its upper pitchers are markedly smaller and have a peristome that is significantly narrower, bears distinct ribs, and has an undulate margin. In addition, the upper pitchers of N. jacquelineae are not known to be yellow throughout, a colouration that is characteristic of N. flava. With N. inermis, this species shares similarly infundibular pitchers, a narrow lid, and the habit of rapidly transitioning from a rosette to a climbing plant (with associated sudden internode elongation). Furthermore, the seedling pitchers of these two species can appear quite similar. Nepenthes inermis differs most obviously in having upper pitchers that completely lack a peristome and in lacking conspicuous glands on the underside of the lid. The describing authors considered N. flava to likely represent an evolutionary link between the pair of N. inermis and N. jacquelineae and "common Sumatran species such as N. ovata". They further speculated: Nepenthes flava might represent an intermediate between N. ovata of northern Sumatra and the unusual N. inermis of the western Sumatran mountains, and would confirm Danser’s hypothesis in which he united common species familiar to him, i.e. N. bongso, N. carunculata Danser and N. singalana, with the distinctive species N.