Dimensions, Birefringences, and Force-Elongation Behavior of Major and Minor Ampullate Silk Fibers from Orb-Web-Spinning Spiders—The Effects of Wetting on these Properties

The effects of wetting by water were determined on the dimensions, birefringences, and force-elongation behavior of major and minor ampullate silk fibers from Araneus diadematus Clerck, and major only from Araneus sericatus Clerck and Araneus gemma (McCook) (all family Araneidae). The values obtained at room conditions (RC), in the wetted, restrained (WR) and wetted, axially unrestrained (WU) states, the ratios of these, between states, are reported upon. The unexpected supercontraction of major ampullate fibers, WU, is contrasted with the stabile behavior of those from the minor ampullate gland systems. When dried from the WR state, both types appear to recover their RC properties. But when dried slack from the WU state, the major ampullate fibers undergo the “drawing” phenomenon typical of many man-made protofibers. The techniques required in order to secure data on these fragile (diameters, 0.6–6.0 μm) fibers, are described in some detail.