Table 1.

Statistical results for friction forces and shear stresses (force per projected contact area) for smooth pads (N. cinerea) and hairy pads (G. viridula). Page's L-test was used to identify changes in shear force/stress with increasing pillar spacing. When a trend was present, consecutive pillar spacings were compared using pairwise Wilcoxon signed rank-sum tests.

	pillar height (µm)	Page's L-test	pairwise Wilcoxon signed rank-sum tests for consecutive pillar spacings (µm)
			3 versus 4	4 versus 6	6 versus 8	8 versus 12	12 versus 22
Nauphoeta cinerea
friction force	0.5	L6,10 = 686 p > 0.05	—	—	—	—	—
shear stress	0.5	L6,10 = 706 p > 0.05	—	—	—	—	—
friction force	1.4	L6,10 = 845 p < 0.001	0.110	0.002	0.920	1.000	0.850
shear stress	1.4	L6,10 = 836 p < 0.001	0.084	0.002	0.920	0.130	0.850
Gastrophysa viridula
friction force	0.5	L6,11 = 976 p < 0.001	0.007	0.007	0.067	0.067	0.320
shear stress	0.5	L6,11 = 981 p < 0.001	0.083	0.007	0.042	0.054	0.410
friction force	1.4	L6,15 = 34.5 p < 0.001	0.190	<0.001	0.140	0.055	0.980
shear stress	1.4	L6,15 = 32.2 p < 0.001	0.035	<0.001	0.140	0.150	0.800