Table 1.

Measured advancing contact angles and calculated surface energies for the majority of test surfaces on which the pulling forces of the beetles were measured

GlassPhotographic paperDry PhragmitesFresh PhragmitesFresh Glyceria
Contact angle with water (degrees)37.3±0.147.2±0.3127.9±0.6132.4±7.1136.3±1.6
Contact angle with di-iodomethane (degrees)59.3±0.155.6±0.7104.5±0.6109.1±2.5111.0±1.9
Total surface energy (mN m-1)*58.1351.327.145.875.32
Polar component (mN m-1)42.4632.420.080.120.01
Dispersive component (mN m-1)15.6618.907.065.755.31
Surface polarity (%)70.0463.
  • The values of the contact angles are means ± S.D. N is number of samples measured.

    For each sample, 35-52 single measured values were recorded automatically.

  • * Since the surface energies of natural solids are always composed of both energy and texture contributions, the calculated surface energies must not be considered as absolute values, which can only be determined for perfectly smooth surfaces.

  • Calculated as (polar component of surface energy/dispersive component of surface energy)×100.