A COMMUNITY ANALYSIS OF THE WEB-BUILDING SPIDERS IN TEMPERATE AND TROPICAL FORESTS WITH EMPHASIS ON THE RELATIONSHIPS BETWEEN FORAGING ACTIVITIES, PREY ABUNDANCE, AND HABITAT STRUCTURE

A guild approach to community structure was used in this study of the web-spider species assemblage in tropical and temperate forests. The foraging activity of orb-web, tangle-web, and sheet-web spiders was determined in a visual search of undergrowth vegatation. Prey activity was monitored in adhesive traps. The vertical distribution of vegetation provided a measure of habitat structure.; The peak spider activity times were parallel to the peak insect activity times in the temperate forest. However, spider activity times were not parallel to insect activity times in the tropical forests. Six hypotheses were suggested to explain this discordance. Some experimental evidence suggests that predation by birds may influence the activity times of tropical spiders.; In a multiple stepwise regression analysis insect abundance and the amount of vegetation in a particular area were the best predictors of the number of spiders active during most time periods on all sites. Enclosure experiments indicate that the density of spiders that occupy an area is directly related to both the number of insects available as prey and the number of web sites in the area. Orb-web weavers and tangle-web weavers reached higher densities than sheet-web weavers in all experimental treatments. Preliminary social behavior was observed in five spider species at very high prey densities.; The proportion of the active spiders found in tangle webs was positively correlated with the evenness of the vertical vegetation profile. The proportion of spiders in orb webs was negatively correlated with the evenness of the vertical vegetation profile. The proportion of spiders in sheet webs was not significantly related to any measured parameter.; This research indicates that the guild approach to spider community analysis is very useful in determining the factors critical to these organisms. The consistency of the results obtained here combined with results from many other studies on spider ecology provide evidence that the fundamental organization of the web-spider community is at the guild level.