Vertical Stratification in Orb‐Web Spiders (Araneidae, Araneae) and a Consideration of Other Methods of Coexistence

Measurements of the web height and counts of the number of webs on randomly selected plots in lespedeza fields reveal that immature Argiope aurantia and Argiope trifasciata, very large araneid spiders, place their webs at different heights. In late summer this vertical stratification disappears, while the numbers of the two species on plots become positively correlated. Coexistence of the two spider species may depend in part upon the usual occurrence of high mortality during the immature stages. Invasion of webs by araneids is reported as possible competitive interference. The two larges species of European araneids also show vertical stratification only as immatures. However, the niches of most Polish Araneus species in fields seem differentiated by parameters related to prey size: season of breeding and size differences between species.