Fig. 1.

Microstructural characterization of the exoskeleton from the flower beetle, T. flammea. (A) Dorsal view of a red-colored T. flammea beetle. Image credit: Eva Nie (photographer). (B) Cross-sectional SEM image of the beetle’s elytra revealing the exocuticle (Exo) and endocuticle (Endo) layers. N represents the normal direction. (C) SEM image of the photonic structure in the exocuticle layer (boxed region in B). The white arrows mark the multilayer region. (D) The photonic multilayer is characterized by two structural parameters: p, period of the horizontal multilayer, and α, inclination angle. (E and F) False colored map of the multilayer period and orientation based on C. (G) Horizontal SEM image of the exocuticle showing the distribution of vertical micropillars. Two structural parameters are defined: r, the radius of the micropillar, and L, the spacing between adjacent pillars. The methodology for determining r and L is discussed in the Materials and Methods. (H) Low-magnification optical image of the cuticle polished in the horizontal orientation, which shows the upper photonic region and the lower micropillar-only region. Inset depicts the slightly inclined orientation of the polishing. (I) 3D model of the identified photonic microstructure consisting of a photonic multilayer laced with vertical micropillars. (J) Elastic modulus map based on AFM measurements. (K) Statistical analysis of modulus based on J.