Figure 6.

(a) Partitioning of the relative work of prey stopping by orb webs. The fraction of work performed by each route was independent of relative impact energy (aerodynamic damping F = 2.99, p = 0.17, radii F = 1.37, p = 0.29, capture spiral silk F = 0.13, p = 0.73). Fraction of work was calculated as the total energy absorbed by that specific route divided by the total energy input to the web. Relative impact energy was calculated as (total energy absorbed (μJ)/spider body weight (mg)) to account for differences in web sizes. Relative impact energy is a measure of the ‘difficulty’ of the catch. Symbols indicate the mean and bars indicate the confidence intervals of each estimate as calculated from propagation of error, with the capture spiral and aerodynamic bars shifted slightly to the right, respectively, so as not to overlap. Internal dissipation by radii was sufficient to account for all energy absorption in six of eight trials, indicated by a fraction of work that included unity (1) in the confidence interval for that estimate. Boxes and dotted line indicate the two impacts in which the projectile broke through the web. (b) Fraction of work by each of the three energy dissipation routes did not depend on spider body weight (radii F = 0.08, p = 0.78, capture spiral F = 0.69, p = 0.44, aerodynamic F = 0.46, p = 0.53). Capture spiral and aerodynamic work were only important in some smaller spiders. However, aerodynamic work was always rather low, and never exceeded 30% of total energy input to the web. Blue diamond, radii; red square, capture spiral; green triangle, aerodynamic dissipation.