Concern over declining biodiversity and the implications for continued provision of ecosystem services has led, recently, to intense research effort to describe relationships between biodiversity and ecosystem functioning. Here we extend this effort to the relationship between natural enemy species diversity and natural pest control. From simple modelled food-webs and simulations of natural enemy species loss we derive specific predictions concerning the effect of herbivore life-history traits, such as life-cycle type and concealment, on the shape (reflecting diversity effects) and variance (reflecting species composition effects) of the relationship between natural enemy diversity and pest-control. We show that these predictions are consistent with the emergence of different pest types following intensification of rice production in Asia. We suggest that basic biological insights can help define the structure of ecological processes and allow more accurate predictions of the effect of species loss on the delivery of ecosystem services.