Dragline use by an orb web spider (Nephila clavipes) was analysed by observing both intact spiders and those prevented from producing a dragline. The behaviours observed were those associated with returning to the web hub and prey capture. Upon returning to the hub, spiders resume the resting position by rotating within the hub, producing several new dragline attachment points during the rotation. The importance of the spider's use of the dragline was made clear by preventing experimental animals from producing the dragline. During resting, the permanent dragline-to-web attachment enabled the spider to maintain the correct posture. Prey capture behaviour was adversely affected in spiders prevented from using the dragline: without a dragline, all relevant components of the behaviour required more time to perform, and movements within the web (e.g. toward prey and back toward the hub) were directed less accurately. The benefit of the dragline to the spider, in terms of safety, time, energy and reduced exposure to predators, is likely to be significant.
