Background/Question/Methods: Much of the rich complexity of natural communities in both their structure and dynamical dynamics emerges from the interaction of natural enemies – e.g., predators, parasites, and herbivores – with their victims – e.g., prey, hosts, or food plants.  This talk will address the issue of whether or not there is a general theory of natural enemy-victim interactions, rather than say a collection of loosely arranged, more specialized theories.

Results/Conclusions: There are clearly some general principles governing such interactions which arise from the fundamental constraints of thermodynamics and conservation of mass.  Beyond these, ecologists have now developed a conceptual framework for understanding in general when to expect oscillatory dynamics, versus regulation to a stable equilibrium.  This framework, which involves the interplay of density dependent feedbacks and heterogeneity, seems robust, but some ecologist still question its generality, and particular natural enemy-victim systems often have idiosyncratic structural features that are crucial to understanding their persistence and dynamics.  These details are particularly important when relating the theory of predator-prey interactions to the theme of diversity and species coexistence.