Elytra coupling of the ladybird Coccinella septempunctata functions as an energy absorber in intentional falls
Jie Zhang, Qiufeng Yuan, Yiling Jiang, Hong Pang, Hamed Rajabi, Zhigang Wu and Jianing Wu
在自然界中，动物利用纷繁复杂的生存策略适应生存环境，某些动物具备有效降低冲击伤害的特殊结构，如山羊角与啄木鸟头骨等。这些“能量吸收器”能够使动物在争夺领地、获取食物等场合最大限度地降低冲击对其组织、结构的伤害，并以此提高生存率。
类似地，七星瓢虫坚硬鞘翅能够保护柔软的腹部和脆弱的后翅免受伤害。例如：当瓢虫从接近0.5 m的高度坠落至地面时，长度仅7 mm的它们并不会因从体长70倍的高度着陆受到的剧烈冲击而丧命。针对这一现象，原有研究认为，瓢虫可以依赖鞘翅的层状结构吸收着陆冲击的能量。然而，关于瓢虫鞘翅之间的连接结构（即：“榫卯结构”）对于能量吸收的作用仍有待揭示。
近日，中山大学航空航天学院吴志刚教授、吴嘉宁副教授课题组，联合中山大学生态学院、中国地质大学（北京）、英国伦敦南岸大学学者，共同研究了七星瓢虫鞘翅间连接结构对冲击能量吸收的作用，并将此成果发表在国际仿生学知名期刊《生物灵感与仿生学》（Bioinspiration & Biomimetics）。
研究借助高速相机发现了七星瓢虫鞘翅连接结构在着陆前后的“连接-分离-连接”状态，评估了七星瓢虫在此过程中的机械能损失，结合碰撞动力学分析了七星瓢虫鞘翅间连接结构的分离能够使鞘翅增加大约33%的冲击能量吸收。仿照瓢虫鞘翅间“榫卯结构”吸能原理，课题组研制了一款可用于无人机坠落的防护装置，并通过实验证明了当连接结构分离时能够降低无人机受到的冲击力，对无人机等飞行器的抗震防护具备显著意义和较好的应用前景。
来源：科学网
Abstract
Some insects, such as bees, wasps, and bugs, have specialized coupling structures to synchronize the wing motions in flight. Some others, such as ladybirds, are equipped with coupling structures that work only at rest. By locking elytra into each other, such structures provide hindwings with a protective cover to prevent contamination. Here, we show that the coupling may play another significant role: contributing to energy absorption in falls, thereby protecting the abdomen against mechanical damage. In this combined experimental, numerical and theoretical study, we investigated free falls of ladybirds (Coccinella septempunctata), and discovered that upon collision to the ground, the coupling may fail and the elytra may unlock. This unlocking of the coupling increased the energy absorption by 33%, in comparison to when the elytra remain coupled. Using micro-computed tomography scanning, we developed comparative models that enabled us to simulate impact scenarios numerically. Our results showed that unlocking of the coupling, here called elytra splitting, reduces both the peak impact force and rebound velocity. We fabricated the insect-inspired coupling mechanism using 3D printing and demonstrated its application as a damage preventing on system for quadcopters in accidental collisions.
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