Microstructure and material properties of hind wings of a bamboo weevil Cyrtotrachelus buqueti (Coleoptera: Curculionidae).

Wings of flying insects, as representative biomaterials, are composed of a flexible membrane and a stiff vein structure that are prone to bending and deformation under aerodynamic forces. Therefore, we must investigate the application value of insect wings in the field of engineering design from the perspective of bionics, which is a new challenge. In this study, we measured the mechanical properties of the hind wings of Cyrtotrachelus buqueti including "dried" and "fresh" samples. The wing membrane samples were prepared by carefully cutting the hind wings into 2.0 mm by 8.0 mm rectangular segments using a gauge. As the major wing veins are the main loading units under aerodynamic forces, we also separated them from the wings as a kind of investigative specimen. The wing membranes were adhered to a specially designed paper fixture and the mechanical properties of the wing veins and membranes were evaluated using a tensile testing machine. We observed the microstructure of the samples using a scanning electron microscope and accurately measured the thicknesses of desired the wing membranes and veins. The results show that there is a difference in the mechanical properties of the two samples. The elastic modulus and Poisson's ratios vary over the region in hind wing, so we can conclude that the wing membrane is an anisotropic and non-uniform material.