COLLIN, M. A.*; SWANSON, B. O.; HAYASHI, C. Y.; Univ. of California, Riverside ; Pacific University, Oregon; Univ. of California, Riverside: Mechanical Properties of Embioptera Silk

Arthropods produce and use silk for a variety of purposes. Silk from a few types of arthropods have been mechanically tested and some of these silks were found to be exceptionally strong, lightweight, and extensible. Embioptera (webspinners) are an order of paurometabolous, subsocial insects that has been little studied. Other investigations of insect silks have focused on orders that are distantly related to Embioptera, namely Lepidoptera (moths), Diptera (flies), and Trichoptera (caddisflies). Embiids are unique because they produce silk throughout their lifetime, unlike other insects, which use silk during just one developmental stage. The primary function of embiid silk is for the construction of silken galleries and foraging tubes. We mechanically tested embiid silk from 15 individuals of Haploembia solieri. The mean diameter of the silk fibers was 0.86 � 0.31 micrometers. The tensile strength of the silk measured 159 MPa � 70. Compared to other arthropod silks, this is one of the weakest fibers tested to date. While individual Haploembia silk fibers are small and weak, embiids make sheets from these fibers and layer the sheets to construct sturdy galleries. Our future studies will include comparative mechanical analyses of silks spun by phylogenetically and ecologically divergent embiids. We will also characterize the silk protein coding genes from these insects. The comparison of molecular sequences and material properties of embiid silks, which are spun from tarsal glands, to lepidopteran and dipteran silks (spun from modified salivary glands) and spider silks (spun from abdominal glands), will improve our understanding of the multiple evolutions of arthropod silks.