Figure 3.
(a) Pads that slid left behind trails of contact-mediating fluid. (b) Adhesive force of pads that slid over different distances, prior to the detachment at 150°, significantly increased with sliding distance (repeated measures ANCOVA, F1,37 = 20.1, p < 0.01, n = 10). (c) Sliding distance of stick insect pads prior to detachment in adhesion tests where shear forces equivalent to one body weight were applied. Because pad area grows more slowly than mass, larger insects are more likely to slide. Sliding occurred only for insects weighing more than approximately 20 mg, consistent with a simple estimate based on the pad allometry and the static shear stress (see the main text). Because sliding increases adhesive strength, the variable sliding distance of pads helps large animals to attach safely, while small animals can still detach their pads effortlessly. (Online version in colour.)