Insects that can walk on smooth surfaces have specialized structures, footpads, on their legs. Footpads play an important role in adhesion to the substrate surface. Although the morphology and function of footpads have been studied, the mechanism of their formation is still elusive. In the ladybird beetle (Harmonia axyridis), hairy footpads are present on the first and second tarsal segments of the legs. The footpads are covered with hundreds of hairs, i.e. setae, whose tips consist of four types: pointed, lanceolate, spatular, and discoidal. We examined the formation of the footpad during the pupal stage using immuno-staining and fluorescent-conjugated phalloidin staining. We found that a seta was composed of a shaft and a socket and some setae were accompanied by a neuron. By the mid-pupal stages, the shaft cells elongated to form a setal structure. Cytoskeletal actin bundles ramified to create a framework for the setal tip structure of the cells. We examined the effects of the application of cytochalasin D, which inhibits actin polymerization, on the formation of footpad setal structures. The results showed that the setal tips were deformed by the inhibition of actin polymerization. Our observations reveal that cytoskeletal actin filaments are involved in shaping the setae.

可以在光滑表面上行走的昆虫的腿上有专门的结构，即足垫。脚垫在与基材表面的粘附方面起着重要作用。尽管已经研究了足垫的形态和功能，但它们的形成机制仍然难以捉摸。在瓢虫甲虫（Harmonia axyridis)，腿的第一和第二跗骨节上有毛足垫。足垫上覆盖着数百根毛发，即刚毛，其尖端由四种类型组成：尖头、披针形、匙状和盘状。我们使用免疫染色和荧光偶联鬼笔环肽染色检查了蛹期足垫的形成。我们发现刚毛由轴和窝组成，一些刚毛伴随着一个神经元。到中蛹阶段，轴细胞伸长以形成固定结构。细胞骨架肌动蛋白束分支为细胞的刚毛尖端结构创建框架。我们研究了抑制肌动蛋白聚合的细胞松弛素 D 的应用对足垫刚毛结构形成的影响。结果表明，由于肌动蛋白聚合的抑制，刚毛发生了变形。我们的观察表明，细胞骨架肌动蛋白丝参与了刚毛的形成。