Mechanical properties of the exocuticle and sections of Cybister elytra

The mechanical properties of elytra without epicuticle and sections of Cybister' s elytra were studied. The hardness and elastic modulus of elytra without epicuticle were obtained from the nano-indenter tests and the values are (0.065±0.007) GPa and (0.704±0.013) GPa, which are much smaller than the values of elytra with epicuticle. The mechanical properties of elytra sections follow some rules: On the transverse section, the hardness and elastic modulus in the coupling zone are slightly larger than those in the central and outer zone; and on the longitudeinal section, the hardness and elastic modulus in the central zone are apparently larger than those in the cephalosome and empennage zone.