above sea level. Nepenthes eustachya usually grows in open, sunny sites on cliff faces and steep slopes at the forest margin. It is restricted to sandstone substrates and often grows on bare rock. Where the species does occur it is common and may form dense clumps, such as those growing beside the road from Sibolga to Tarutung in North Sumatra. Nepenthes eustachya grows in close proximity to a number of other lowland species, including N. albomarginata, N. ampullaria, N. gracilis, N. longifolia, and N. sumatrana. It is known to hybridise with all of these species. The conservation status of N. eustachya is listed as Least Concern on the 2006 IUCN Red List of Threatened Species. Related species Nepenthes eustachya differs from N. alata in a number of morphological features. Jebb and Cheek outlined these differences when they restored the former as a valid species. Nepenthes eustachya has a lanceolate lamina with a rounded to sub-peltate apex, whereas that of N. alata is lanceolate-ovate with an acute or attenuate apex. The petiole also serves to distinguish these species: in N. eustachya it is scarcely or not winged at all, whereas in N. alata it is broadly winged. The pitchers of N. eustachya bear a simple or bifurcate spur, compared to the simple and acutely pointed appendage of N. alata. Mature parts of N. eustachya are glabrous, while N. alata bears an indumentum of reddish or whitish hairs. Jebb and Cheek also compared the structure of the pitcher base: that of N. eustachya is angular and woody, being gradually attenuate towards the tendril. The base of N. alata traps, however, has a similar texture to the rest of the pitcher and is abruptly attenuate towards the tendril. Nepenthes alata exhibits great variability across its range and it is inevitable that some plants will deviate from the characters outlined by Jebb and Cheek. However, the overall combination of morphological differences appears to be stable and it is this that demarcates these species. Nepenthes eustachya bears a superficial resemblance to N. mirabilis. It can be distinguished from that species on the basis of its lower pitchers, which lack wings, its fimbriate leaf margins on short shoots, and coriaceous leaves, as opposed to chartaceous in the latter. Charles Clarke notes that the upper pitchers of N. eustachya, which have a pronounced globose base, may resemble those of N. clipeata from Borneo and N. klossii from