Figure 1.
Morphology of N. gracilis pitchers.
(A) N. gracilis pitcher with visiting Polyrhachis pruinosa ant, showing the epicuticular wax crystal surfaces on the inner pitcher wall and on the underside of the pitcher lid. (B) The horizontal orientation directly above the pitcher opening puts the lower lid surface in an ideal position for prey capture.
Figure 2.
Contribution of the individual N. gracilis pitcher surfaces to prey capture under different environmental conditions.
(A) Experimental setup to test how rain drops falling onto the pitcher lid affect ant capture. (B) Proportion of ant visitors to each pitcher surface that fell into the pitcher, under ‘dry’, ‘raining’, and ‘wet’ treatment condition, respectively. The interaction of pitcher surface and experimental condition was highly significant (P<0.001).
Figure 3.
Biological relevance of the lid capture mechanism.
The natural prey capture rate of pitchers with a non-slippery PDMS coating applied to the lower lid surface is reduced in comparison to the untreated control group (*: P<0.05).
Figure 4.
Microscopic structure of the wax crystal surfaces.
(A–B) Microstructure of the crystalline wax layer on the inner pitcher wall. (A) Top view, showing a dense network of thin, upright wax platelets (scale bar: 5 µm). The freeze-fracture side view (B) reveals the internal organisation of the surface (scale bar: 2 µm). (C–D) Microstructure of the lower lid surface. (C) Top view: the wax crystals form solid, pillar-like structures, unevenly distributed across the surface and surrounded by smooth cuticle (scale bar: 5 µm). (D) Side view of the wax pillars (scale bar: 2 µm).
Figure 5.
Area-specific nectar secretion onto the peristome and the lower lid surface.
N. gracilis pitchers secrete significantly larger amounts of nectar under the lid than those of sympatric N. rafflesiana (***: P<0.001).