Arthropod silk is a protein-based fiber used by spiders and insects for a myriad of functions, such as: egg-sac production, retreat construction, and prey capture. Silks involved in prey capture, however, are among the strongest, stretchiest, and toughest materials known to nature along with impressive adhesive properties that have provided a source of bio-inspired design for materials engineers. Whilst decades of research have greatly improved our knowledge of the mechanisms that drive these mechanical properties, their evolution and biological importance, fundamental questions still remain understudied or completely unaddressed. How does animal ontogeny influence silk properties? How do harsh environmental conditions affect silk adhesiveness? What are the roles of each silk fiber component in sticky composite threads used to adhere insect prey? To address these questions, four independent studies were conducted using two species of web-building spiders (Tasmanian cave spider Hickmania troglodytes and Taiwanese lace-sheet spider Psechrus clavis) and the Tasmanian glowworm Arachnocampa tasmaniensis. Frame silk of H. troglodytes webs becomes stronger and tougher as individuals grow larger and adhesiveness of their sticky cribellate threads increases when the underlying axial fiber becomes more compliant. Glue-coated capture threads of A. tasmaniensis are virtually non-functional outside of their native wet cave environments. Finally, constituents of cribellate silk from P. clavis have previously unreported roles in increasing work to fracture of the entire thread. These studies will springboard future work into the ecological and evolutionary consequences arising from or producing the observed trends along with providing inspiration for novel composites and fiber-based materials.
