The toughest recorded spider egg case silks are woven into composites with tear-resistant architectures.

In this communication, we report important preliminary evidence for possibly the toughest egg case silk threads recorded to date spun by the hermit spider, Nephilengys cruentata (G¯=193MJm(-3)). We further elucidate that the egg case itself is woven with a specialised repeat cross-weave that when subjected to tension, drives perpendicular-to-force threads to pile. This piling of threads constrains damage to small areas and retains the architectural integrity of the surrounding egg case material. We deduce that by having ultra-tough threads coupled to a tear resistant architecture, N. cruentata is able to protect its eggs from predators with a considerable level of effectiveness.