Behavioral response of Argiope trifasciata to recent foraging gain: A manipulative study

This study investigates how recent foraging gain affects the web-building b ehavior of the garden spider, Argiope trifasciata, especially stabilimentum -building. Adult female spiders in the field and in cages were randomly ass igned 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 ex periment was terminated after each A. trifasciata had built four consecutiv e webs; the number of days required by each spider was recorded. During the experiment I recorded silk length, catching area, mesh size and stabilimen tum area of each web spun by test spiders. Continuously fed, field and cage d spiders decreased silk output and web size, increased mesh size and incre ased the interval between successive foraging bouts. Unfed, caged spiders i ncreased silk output and web size, maintained mesh size and shortened the i nterval between successive foraging bouts. Although unfed spiders in the fi eld exhibited the same trend, changes in the web characteristics were not s tatistically significant. Stabilimentum size of fed caged spiders was great ly enhanced, but that of field spiders was unaffected. The size of stabilim enta built by unfed spiders in both field and cage was unaffected by the tr eatment. These results indicate that Argiope trifasciata do not alter size of stabilimenta in response to recent foraging gain alone, and factors othe r than food intake are involved.