ABSTRACT

Colonial, or territorial permanent–social, web–building spiders in the orb–weaving families Araneidae and Uloboridae exhibit a combination of solitary and social behavior. These spiders maintain individual territories within the aggregation or colony and do not disperse before reaching reproductive maturity. Although all colony members contribute to the communal silk framework of the colony to some degree, each individual builds, occupies and defends its own orb web, and prey are usually not shared. In this chapter, we focus on the ecological conditions and behavioral characteristics that influence the evolution of sociality. We describe and compare the web structure and group–living arrangements seen in a variety of orbweaving species, as well as apparent behavioral transitions from simpler to more complex forms of social behavior within taxa.

Long–term ecological research on a single taxon (Metepeira) has identified the primary benefits (enhanced prey capture and reduced silk costs) and costs (increased rates of predation and egg–sac parasitism) of groupliving. Here, we present new data from our research on one species in this genus (M. incrassate) and examine how these benefits and costs vary with group size and affect individual fitness.

Extensive research on a variety of spider taxa suggests that differences in life histories and the internal organization of colonies (regarding web territories and communal retreats) reflect divergent subsocial and parasocial pathways to the evolution of group–living. However, there remain a number of unanswered questions concerning the genetic structure of colonial web–building spider populations.