Web-building spiders are in the unique situation where they reside in the middle of their web and are therefore relatively exposed to predators. All rights reservedĪnimals are able to assess the risk of predation and respond accordingly via behavioural and physiological changes. Despite the increase in detectability, incorporating a conspicuous cruciform decoration to the web effectively defends the spider by diverting the attack towards the decoration or leg, but not by camouflaging or intimidating, thus, supporting the deflection hypothesis. When both spiders and decorations were present, chicks also attacked the spider main bodies and their legs or decorations, and not randomly: they attacked the legs or decorations sooner and more frequently than they attacked the main bodies, independence of the ratio of the surface area between the decoration and spider size. Chicks attacked the spider main bodies significantly less frequently on the decorated webs than on the undecorated webs, thus reducing predation risk. Spider bodies and decorations were conspicuous against natural backgrounds to the avian visual systems. Then we determined actual predation risk on spiders using naïve chicks as predators. We employed visual modelling to quantify the conspicuousness of spiders and decorations from a perspective of avian predators. Here we tested this hypothesis using the X-shaped silk cruciform decorations built by females of Argiope minuta. However, empirical evidence for this deflection function remains limited. The decorations may also deflect predator attacks from spiders. These conspicuous decorations are hypothesized to deter predators by warning the presence of sticky webs, camouflaging spiders, acting as a decoy, or intimidating predators by their apparent size. Many orb-web spiders adorn their webs with extra, bright white silk. Since stingless bees respond similarly to different levels of signal strength, I conclude that variation in decorations does not affect prey interception.Īlthough camouflage as an effective antipredator defence strategy is widespread across animals, highly conspicuous color patterning is not uncommon either. I also demonstrate that the likelihood of prey hitting the capture area is greater than that of hitting the hub area in decorated webs. I show that stingless bees (Trigona carbonaria) respond to the silk decorations of Argiope keyserlingi Karsch 1878 in similar ways irrespective of the pattern of decorations. In this study, I tested the response of bees to varying decoration patterns. The prey attraction hypothesis implies that as the signal changes, so should the response of the intercepting insects. By varying the decoration pattern, spiders minimize the potential predation costs of constructing a highly visible signal and deter potential prey such as bees from associating decorations with danger. Two main hypotheses, (prey attraction and predator avoidance) have had intermittent support and criticism. The functional significance of web decorations in orb-web spiders has been an area of intense study for well over a hundred years. Thus, we argue that the solution of the riddle of web decorations might reside in the physiology of molting spiders. 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. 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. The most striking result was that subadult spiders built dramatically oversized decorations prior to the last molt. We found substantial individual variation of web decorations of A. 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. Molting events are major physiological transitions combined with fundamental alterations of the metabolic state of the spiders. Physiological processes may influence individual variation in web decorating behavior. Web decorations can differ in shape, size, and frequency across species and even within species. 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. In the araneid genus Argiope, these web decorations consist of flimsy aciniform silk threads arranged in zig zag shaped bands. Various orb weaving spiders decorate their webs with extra silk structures.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |