This layer is not as thick as, and structurally distinct from, that found in the waxy zone of the pitcher interior, and insects can easily adhere to it in dry conditions.

During downpours, however, it functions as part of a trapping mechanism, whereby the impact of raindrops striking the lid causes insects to lose their footing and fall into the pitcher cup below.

[15] Centre: Scanning electron micrographs revealing the ultrastructure of N. gracilis wax crystals on the inner surface of the pitcher (A and B) and underside of the lid (C and D).

One of the most widespread Nepenthes species, N. gracilis is native to Borneo, Cambodia,[6] Peninsular Malaysia, Singapore, Sumatra, central Sulawesi, and southernmost Thailand.

[19] In 2001, Charles Clarke performed a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia using 70 morphological characteristics of each taxon.