Structural characteristics of the core layer and biomimetic model of the ladybug forewing

To explore the characteristics of the core structure of ladybug (Harmonia axyridis) forewings, their microstructure was studied using microscopes. The results suggest that trabeculae exist in the frame of the beetle (ladybug) forewing for the first time; this study represents the first determination of the parameters N, the total number of trabeculae in each forewing, and λ_t, the ratio of the cross-sectional area of the trabeculae to the effective area of trabecular distribution. The cross-sectional area of a single trabecula in the ladybug forewing is smaller than those in two other kinds of beetles, Allomyrina dichotoma and Prosopocoilus inclinatus. However, the average trabecular density of the ladybug forewing is 84 per square millimeter, which is the highest among these three kinds of beetles. The λ_t values are 1.0%, 1.5% and 10.5% for H. axyridis, A. dichotoma and P. inclinatus, respectively, and the corresponding N values are approximately 1.4, 1.7 and 3.7 thousand, respectively. Based on these findings, a biomimetic model of the ladybug forewing is proposed, which is characterized by a core structure with a high-density distribution of thin trabeculae surrounded by a foam-like material.