Carnivorous plants have close associations with other species that live in or on the plant. Sarracenia purpurea has a particularly large number of inquiline species, many of which are obligates that live in its water-filled leaves. These include a well-studied food web of bacteria, protozoa, rotifers, mites, and Diptera larvae, all of which depend on the prey of the host plant. This model system has been used to address fundamental questions in ecology and evolution, including studies of keystone predation, succession, consumer versus resource control, invasion, dispersal, and the roles of resources and predators in metacommunities. The microecosystem also has been used to understand density-dependent selection, the genetic structure of populations, evolution over climatic gradients, and evolution in a multispecies, community context. In this chapter, the ecology of this potentially mutualistic contained community is explored in the context of its carnivorous host.