Geometrical features and wettability of dung beetles and potential biomimetic engineering applications in tillage implements

Dung beetles can break up dung pads and compact dung into balls and their cuticle surfaces do not stick dung or soil. The geometrical features of some dung beetles and wetting behavior of the pronotum cuticle surfaces of the dung beetle Copris ochus Motschulsky were investigated. It was found that dung beetles have embossed textured surfaces on their pronotum, clypeus and elytra. The head of dung beetles have shapes similar as bulldozing blades. The forelegs of dung beetles have a tooth-like structure with strong burrowing ability. The number and/or the size of the teeth of the forelegs are dependent upon the species of dung beetles. The pronotum surface profiles of the tested dung beetle C. ochus Motschulsky displayed approximately a statistical fractal character and the estimated fractal dimension of the pronotum surface profile was 1.877. The wetting tests showed that the apparent contact angles of water on the pronotum surface of the dung beetle C. ochus Motschulsky were 91-106.5° and the average contact angle was 97.2°, representing a hydrophobic property. Some potential engineering applications of the geometrical features of dung beetles and the wetting behavior of their cuticle surfaces in biomimetic designs of tillage implements were discussed.