The orb web is a spectacular evolutionary innovation that enables spiders to catch
flying prey. This elegant, geometric structure is woven with silk fibers that are
renowned for their superior mechanical properties. We used silk gland expression libraries
to address a long-standing controversy concerning the evolution of the orb-web architecture.
Contrary to the view that the orb-web design evolved multiple times, we found that
the distribution and phylogeny of silk proteins support a single, ancient origin of
the orb web at least 136 million years ago. Furthermore, we substantially expanded
the repository of silk sequences that can be used for the synthesis of high-performance