Foraging strategies and feeding regimes: Web and decoration investment in Argiope keyserlingi Karsch (Araneae: Araneidae)

The principal foraging cost for web-building spiders is the amount of silk invested in their webs. Spiders in the genus Argiope additionally decorate their orb webs with conspicuous UV-white silk bands, called web 'decorations' or 'stabilimenta', which enhance foraging success by attracting prey to the web. We subjected Argiope keyserlingi Karsch to different feeding regimes and measured their foraging response with respect to the size and design of the orb-web, and the number and length of decorative silk bands. Spiders experiencing low prey encounter rates constructed larger webs and incorporated more silk but fewer web decorations than spiders experiencing high prey encounter rates. When the rate of prey encounter was constant, the spiders increased the amount of silk per web but with little change in the number of decorative bands. In contrast, when prey supply was variable, spiders increased the number of decorative silk bands but not the amount of silk invested in the web.