Do stabilimenta in orb webs attract prey or defend spiders?

Orb-weaving spiders are ideal organisms for the study of conflict between b ehavioral investments in foraging and defense because their webs provide ph ysical manifestations of those investments. We examined the impact of inclu ding stabilimenta, designs of bright-white noncapture silk, at the center o f orb webs for foraging and defense in Argiope aurantia. Our findings sugge st that stabilimentum building is a defensive behavior, supporting the "web advertisement" hypothesis that the high visibility of stabilimenta can pre vent birds from flying through webs. Yet, spiders often do not include stab ilimenta in their webs, indicating that a serious cost is associated with t hem. We also show through comparison of paired webs with and without stabil imenta, that stabilimenta reduce the prey capture success of spiders by alm ost 30%. This demonstrates the potential impact that defensive behaviors of spiders can have on their foraging success and suggests that much of the v ariation in stabilimenta may be accounted for by a cost-benefit trade-off m ade when including stabilimenta in webs.