Some Physical Properties of Brazilian Wild Lepidoptera Silks

Wild moths silk fibers have distinct properties from the widely cultivated Bombyx mori silk and show promising applications in several areas. However, few Lepidoptera species have their silk properly characterized; the studies so far concentrate on a few groups of wild silk moths. In the Lepidoptera group, in addition to the construction of cocoons, the silk is used to construct collective shelters, migration, lifelines, and, in rare cases, to capture prey. Therefore, understanding the composition and properties of these silks can help understand their role in the biology of these species and their possible applications. In this paper, tensile tests and FTIR analysis of silks from seven species were performed, and the results were analyzed by multilinear regression, principal component analysis, and cluster analysis. According to our results and data from the literature, the average Young's modulus for silks from Papilionoidea, Psychidae, Saturniidae, and Sphingidae are 3.5, 21.4, 5.4, and 5.9 GPa, respectively. Furthermore, the silk from Papilionoidea has lower tensile strength than other Lepidoptera. Our results support the correlation between the silk's mechanic properties and beta-sheet polyalanine, beta-sheet polyalanine-glycine, serine, and oxalate concentrations.