The cocoon with a unique hierarchy not only provides a space in which the pupa to adult metamorphosis occurs, but also protects the pupa from weather, predators and parasitoids. In this paper, scanning electron microscope (SEM) is adopted to elucidate the basic geometric properties of the cocoon and silk morphology. Tussah cocoon has a special geometric structure, and its silk fibers have shaped morphology. The fractal calculus is also employed to study the cocoon's thermal property. The cocoon's multiple layer hierarchy and the silk's belt-like cross-section guarantee the cocoon has an extremely good thermal insulation. In addition, an experiment is carefully designed to verify the theoretical prediction, and a domestic silkworm cocoon is used for comparison. Both the experimental and theoretical analyses show that the tussah cocoon's special fractal property leads to an extreme good thermal insulation and can be used for biomimetic design for the protective clothing and coatings.

具有独特等级的茧不仅提供了蛹到成虫变态发生的空间，而且还保护蛹免受天气、捕食者和寄生物的侵害。本文采用扫描电子显微镜（SEM）来阐明茧丝形态的基本几何特性。柞蚕茧具有特殊的几何结构，其丝纤维具有异形形态。分形演算也被用来研究茧的热特性。茧的多层层次和丝绸的带状横截面，保证了茧具有极好的隔热性。此外，还精心设计了一个实验来验证理论预测，并使用家蚕茧进行比较。