Tribological properties of the beetle leg joints

Tribological properties of femoro-tibial leg joints in two beetles, darkling beetle Zophobas morio and Congo rose chafer Pachnoda marginata were studied. Very low friction of 0.004 was revealed by the direct measurements in the joint. It is assumed that semi-solid lubricant functioning as in technical bearings is one of the leading factors of the friction minimization. Dependence of the surface texture and physical chemical properties (hydrophobicity) on the cuticle friction was analysed. Contribution of the surface texture to the tribological properties of contacting surfaces was examined by the measurement in the tribosystem “contacting surface/glass”. It is supposed that coefficient of friction (COF) decreases with decrease of surface roughness. At the same time, no statistically significant correlation was found between the hydrophobicity of the surface and the value of the friction coefficient.