Abstract
Many laboratory experiments demonstrate how orb-web spiders change the architecture of their webs in response to prey, surroundings and wind loading. The overall shape of the web and a range of other web parameters are determined by frame and anchor threads. In the wild, unlike the lab, the anchor threads are attached to branches and leaves that are not stationary but move, which affects the thread tension field. Here we experimentally test the effect of a moving support structure on the construction behaviour and web-parameters of the garden cross spider Araneus diadematus. We found no significant differences in building behaviour between rigid and moving anchors in total time spent and total distance covered nor in the percentage of the total time spent and distance covered to build the three major web components: radials, auxiliary and capture spirals. Moreover, measured key parameters of web-geometry were equally unaffected. These results call for re-evaluation of common understanding of spider webs as thread tensions are often considered to be a major factor guiding the spider during construction and web-operation.
Highlights
IntroductionNumerous studies have examined the intricate features of spider orb webs typically concluding that the features of orb webs are largely dictated by their function as prey traps (Fig. 1) (Burtscheidt et al 2019; Dyson 2018; Krink and Vollrath 2000; Mortimer et al 2014; Nyffeler 2009; Pasquet et al 2013; Rhisiart and Vollrath 1994; Schneider and Vollrath 1998; Souza et al 2007; Uetz et al 1978; Vollrath et al 1997; Wu et al 2013; Zschokke 2011)
A spider remained stationary for multiple extended periods partway through the build resulting in a total construction time of 15119 s, more than twice as long as the longest construction time by any spider (6805 s). As this behaviour was abnormal and created an extreme outlier in terms of web construction time, this run was excluded from the temporal web building analyses. This run was not excluded from the web design analyses and spatial web building analyses because the resulting web design and distances covered were not affected by this behaviour
We found no significant effects of the shearing on both web building and a range of selected web features shown to be affected by blowing wind (Figs. 3, 4 and 5)
Summary
Numerous studies have examined the intricate features of spider orb webs typically concluding that the features of orb webs are largely dictated by their function as prey traps (Fig. 1) (Burtscheidt et al 2019; Dyson 2018; Krink and Vollrath 2000; Mortimer et al 2014; Nyffeler 2009; Pasquet et al 2013; Rhisiart and Vollrath 1994; Schneider and Vollrath 1998; Souza et al 2007; Uetz et al 1978; Vollrath et al 1997; Wu et al 2013; Zschokke 2011). In windy conditions, spiders like the garden cross spider Araneus diadematus alter many web features (presumably in order to minimise wind damage) such as total web area, capture spiral area, web eccentricity, mesh space, capture spiral count, radial count, total radial length and total capture spiral length (Vollrath et al 1997; Wu et al 2013; Fig. 1) In another example, in constrained spaces, A. diadematus modifies many interconnecting key features of web architecture again showing the high degree of flexibility in the spider’s web-construction algorithm (Krink and Vollrath 2000). The potential effects of moving anchors are interesting because spiders carefully manage silk tensions in their
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