The Force-Elongation Behavior of Web Fibers and Silks Forcibly Obtained from Orb-Web-Spinning Spiders

The force-elongation properties of web fibers produced by the major ampullate gland systems of four species of orb-web-spinning spiders have been determined and compared with the corresponding properties of fibers obtained from the same gland systems by forcible silking. Although all such fibers are highly variable in characteristics, on the average the former are possessed of rupture tenacities of the order of 80 g/tex and rupture elongations of 35%, a combination that gives them an extremely great resistance to failure in extension. There is some indication that fibers obtained by forcible silking without carbon dioxide-induced anesthesia are possessed of similar properties. But forcible silking under complete anesthesia results in the formation of fibers of lower tenacity and tends to produce an even greater variability in morphology and physical properties than is found among web mooring-line fibers from the same species. Techniques are described for the preparation of samples of these very small (3 to 5-micron diameters) and therefore very fragile fibers and for making measurements on them.