Fig. 1.

A liquid wire. Whether stretched or relaxed, the typical capture silk thread of an araneid orb spider (here N. edulis) remains taut. Force monitoring reveals that when subjected to large tension T, the fiber behaves like a spring (I). As T is decreased, a force plateau $T\simeq T_{\text{P}}$ is reached, along which the thread adopts a wide range of lengths, just as soap films do (II). At lower tensions, $T<T_{\text{P}}$, the thread is totally contracted (III). See Movie S1 for full cycle.