Optimal area use in orb webs of the spider Araneus diadematus

We studied the abilities of the garden cross spider Araneus diadematus rega rding adaptation of web geometry to spatial constraints. Spiders reacted to a spatial reduction in their building site from a square-shaped frame to a slimmer, rectangular frame (side ratio 1:2) by maintaining overall web geo metry while reducing the web area covered by the sticky capture spiral. How ever, when the frames were changed further to a rectangular side ratio of 1 :3, the spiders changed specific web properties in such a way that a furthe r reduction in the capture spiral area was prevented. Construction of the t hreads making up the web frame and the auxiliary spiral requires that the s pider explores the spatial constraints of its building site. The geometry o f both frame and auxiliary spiral threads in turn determine the geometry of the capture threads. Since in very narrow frames the spider adjusted the a uxiliary to suit the subsequent capture spiral, we suggest that an initial spatial survey led to the final adaptation of overall web geometry to a web site.