PREDATORY BEHAVIOR OF THE SOCIAL SPIDER MALLOS-GREGALIS - IS IT COOPERATIVE

1- In the communal, non-territorial spider Mallos gregalis, large numbers of individuals share communal webs and feed as groups on the same prey. The seemingly cooperative nature of this behavior is critically examined. 2- It is misleading to characterize the behavior of spiders when they contact prey as a cooperative predatory attack since the web, rather than the direct action of the spiders, is evidently the principal factor in subduing prey. Flies landing on webs are trapped for considerable time periods, often indefinitely, even if not contacted by spiders. 3- Predation may be indirectly cooperative through web-building activites, since larger webs built by larger groups of spiders are more effective traps. 4- Since adult males lack functional cribella, they seem to be at least partially parasitic with respect to web building and predation. 5- Some individuals bite flies, then depart after a short period. Other spiders remain and feed on these flies. Possibly, the departing spiders contribute to the handling of prey upon which they do not themselves feed. © 1979 Masson.