Biological control of a particular pest species is seldom a simple system of just one pest species and one natural enemy. Such pest-enemy interactions are in general embedded in richer communities of multiple interacting pests and natural enemies, and those interactions can affect the control of that particular pest species. Especially the role of generalist predators in these natural enemy communities are under debate. On the one hand, they can be very effective by establishing in crops prior to pest invasions, but on the other hand, disrupt the biological control by interacting with other natural enemies (hyperpredation, intraguild predation). In this project we aimed to better understand which characteristics of natural enemies, including generalist predators, and which types of interactions among species are essential for pest suppressive ecosystems in greenhouse crops. Both ecological theory and empirical data about food web complexities can contribute to the design of these biocontrol ecosystems. Based on the literature, these interactions were written down in a scientific paper. Additionally we studied the interactions between two generalist predator species and the interaction between a generalist mirid bug and a specialist aphid predator. Future research will focus on how the nutritional value of different food sources (plant, pest species, alternative food, other natural enemies) will affect their feeding behaviour. This information is crucial for developing and managing resilient cropping systems.