Mechanics of silk produced by loaded

We examined the effect of a spider's weight on silk parameters and material properties by studying the stress strain characteristics of radial fibres from Araneus diadematus made heavier by adding weight or 'centrifugation' in a carousel. Thus loaded, spiders produced thicker, stronger and stiffer threads. However, normalizing for diameter showed that the material properties of these thicker threads were in fact inferior: the increase in diameter was accompanied by a decrease in stiffness (Young's modulus). This suggests that this particular silk may not be a simple, homogeneous rod, as generally assumed.