Nanomechanical and Angle-dependence Optical Properties in Beetle Popillia Indgigonacea Motsch (Coleoptera)

The nanomechanical and angle-dependence optical properties of elytra of Popillia indgigonacea Motsch were studied in this paper. The surface morphology structure and interior microstructure of elytron are investigated by confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM), respectively. There are fish-like scales and pits on the surface of elytron. The interior microstructures are composed of multilayer of epicuticle, and then is feather-like units of exocuticle. The nanomechanical properties were got by nanoindentation technique. The values of reduced modulus (Er) and hardness (H) of the transverse section display a declining tendency from epicuticle to endocuticle, and fluctuant variation for longitudinal section. The relatively higher Er and H of elytron surface play a role in resisting force, and the lower strength is to buffer. Additionally, the optical testing of elytron specimen was conducted by angle-resolved spectroscopy system in different angles from 0° to 60°. The reflectance peak gradually transfers from 588 to 510 nm showing colors of orange, yellow and green when the incidence angle switches from 0° to 60° in multilayer.