Behavioral Ecology Advance Access published online on March 11, 2008
Behavioral Ecology, doi:10.1093/beheco/arn030
Wrap attack activates web-decorating behavior in Argiope spiders
a Institut für Biologie, Bereich Zoologie, Martin-Luther-Universität Halle-Wittenberg, Hoher Weg 4, D-06099 Halle (Saale), Germany b Department of Zoology, University of Melbourne, Melbourne, Victoria 3010, Australia
Address correspondence to A. Walter. E-mail: andre.walter{at}zoologie.uni-halle.de.
| Abstract |
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Various orb-weaving spiders add extra silk structures—"web decorations"—to their webs. The adaptive value of these web decorations is still unclear, and the suite of functional hypotheses remains controversial. Spiders in the genus Argiope decorate their webs with densely woven zigzag ribbons made of fibrous aciniform silk. This type of silk is also used by the spiders for "wrap attacks" to immobilize the prey by wrapping it with a dense silk cover. Previous studies suggested that the spiders use accumulated excess silk for building web decorations due to a constant secretion in the aciniform glands. We test if this hypothesis holds for 3 species, which construct different types of web decorations: linear in Argiope bruennichi, irregular in Argiope sector, and cruciate in Argiope keyserlingi. We show that depletion of aciniform silk has a stimulating effect on web-decorating behavior in 3 species of Argiope. The aciniform glands apparently readily overcompensated experimentally induced silk losses, and so silk depletion may result in the activation of the according glands. We suggest that the aciniform gland activation might be an important mechanism for Argiope's wrap attack to ensure sufficient wrapping of silk under high prey density and repeated wrapping events. The web decorations might function as a mechanism to maintain high gland activity, thereby maximizing the efficiency of the wrap attack strategy of Argiope.
Key words: aciniform silk, Argiope, capture strategy, gland activation, web decorations.
Received 26 September 2007; revised 7 February 2008; accepted 7 February 2008.