Various orb weaving spiders decorate their webs with extra silk structures. In the araneid genus Argiope, these web decorations consist of flimsy aciniform silk threads arranged in zig zag shaped bands. The adaptive value of these structures is still unclear and controversy over a suite of possible functional explanations persists: the high variation of web decoration adds further uncertainty. Web decorations can differ in shape, size, and frequency across species and even within species. Physiological processes may influence individual variation in web decorating behavior. Molting events are major physiological transitions combined with fundamental alterations of the metabolic state of the spiders. For gaining new insights into possible proximate mechanisms driving web decorating behavior, we observed subadult Argiope keyserlingi Karsch 1878 females in the laboratory and registered the individual variation of web decorations associated with the maturity molt under laboratory conditions.

We found substantial individual variation of web decorations of A. keyserlingi. The most striking result was that subadult spiders built dramatically oversized decorations prior to the last molt. Since aciniform silk is used for both constructing web decorations and immobilizing prey we suggest that these extensive decorations might provide a store for the swift replenishment of aciniform silk after the molt. High silk recycling rates make temporary outsourcing less costly and facilitate a rapid resumption of prey capture following lost foraging opportunities during the molting phase. Thus, we argue that the solution of the riddle of web decorations might reside in the physiology of molting spiders.