Spider cocoons and their suspension systems as barriers to generalist and specialist predators

Summary This study tests hypotheses regarding spider cocoons and their suspension systems as barriers to generalist and specialist predators. Evidence presented here suggests that the suspension systems ofMecynogea lemniscata andArgiope aurantia cocoons are effective barriers against small generalists such as ants, but fail to stop large generalists such as birds. Cocoon covers were found to be generally ineffective against generalist predators. Various component layers of these cocoons are shown, however, to be an effective barrier against the attack modes of specific predator guilds. Cocoon covers function primarily as barriers to specialists that use active “burrowing” larvae to gain entrance into the cocoon, while the flocculent silk layer is shown to be an effective barrier against specialists which use a long ovipositor to attack cocoons. These findings support suggestions that the primary role of the cocoon is to provide protection from predators and parasites. These results also support a close evolutionary relationship between cocoon architecture and specialized predators.