Effects of spider size on the probability of bridging. Plots show the probability of bridging predicted by logistic regressions (continuous line) using either a) body mass or b) carapace width as predictor variables. Each dot corresponds to the trial of one single individual (females solid circles, males empty circles). To distinguish between males and females, successful bridging takes the value of 1 for females and 1.05 for males, while unsuccessful bridging takes the value of 0 for females and 0.05 for males. The red arrows show the threshold beyond which the predicted probability of bridging is les than 5%, and the red small vertical lines mark the limits of the confidence interval for this threshold.