A COMPARISON OF AGONISTIC BEHAVIOR OF COLONIAL WEB-BUILDING SPIDERS FROM DESERT AND TROPICAL HABITATS

The agonistic behaviour of two species of colonial spiders, Metepeira sp. a (atascadero), and M. incrassata, from desert and tropical habita ts, respectively, in Mexico, were compared by observing induced intera ctions between immature and/or female spiders at natural web sites. In dividuals of the desert species showed a greater tendency to escalate to potentially damaging behaviour, whereas the tropical species exhibi ted primarily low-intensity aggressive behaviour. In both species, gre ater body mass determined which spider gained possession of the web in unequally matched contests, whereas in equally matched contests, web residents won more often than did intruders. Desert spider conflicts w ere of significantly longer duration than tropical spider conflicts. T he significance of these results for understanding the evolution of so cial behaviour in spiders is discussed. (C) 1995 The Association for t he Study of Animal Behaviour