Behavioral Response of Argiope trifasciata to Recent Foraging Gain: A Manipulative Study

Abstract

This study investigates how recent foraging gain affects the web-building behavior of the garden spider, Argiope trifasciata, especially stabilimentum-building. Adult female spiders in the field and in cages were randomly assigned to two groups, fed and unfed. Spiders in the fed group received three grasshoppers each day; spiders in the unfed group received no prey. The experiment was terminated after each A. trifasciata had built four consecutive webs; the number of days required by each spider was recorded. During the experiment I recorded silk length, catching area, mesh size and stabilimentum area of each web spun by test spiders. Continuously fed, field and caged spiders decreased silk output and web size, increased mesh size and increased the interval between successive foraging bouts. Unfed, caged spiders increased silk output and web size, maintained mesh size and shortened the interval between successive foraging bouts. Although unfed spiders in the field exhibited the same trend, changes in the web characteristics were not statistically significant. Stabilimentum size of fed caged spiders was greatly enhanced, but that of field spiders was unaffected. The size of stabilimenta built by unfed spiders in both field and cage was unaffected by the treatment. These results indicate that Argiope trifasciata do not alter size of stabilimenta in response to recent foraging gain alone, and factors other than food intake are involved.