The effect of food and silk reserve manipulation on decoration-building of Argiope aetheroides

In this study I investigated how decoration-building of Argiope aetheroides is proximately controlled. Since decoration silk is produced from the aciniform glands and these glands' secretion is also used in prey-wrapping, I tested if manipulating the amount of silk in the aciniform glands would lead to changes in the building of decorations. When the aciniform,lands of A. aetheroides were supplemented by giving spiders ample prey and silk was not depleted, a significant increase in total area and number of arms of decorations was found. When the aciniform glands were intensively depleted by repeatedly removing the wrapped prey from webs, the size of decorations in subsequent webs was significantly reduced. Spiders building webs with small or no decorations were still able to produce plenty of silk to wrap prey. Therefore, the presence of undecorated webs seemed to result from the silk reserve, which the spiders may invest on decoration-building, being depleted, rather than the aciniform glands being completely emptied. Based on the results, I propose that there is a threshold point in the aciniform glands, and the amount of silk reserve in the glands relative to that threshold determines the size of decorations.