At least two insects also use the pitchers as a breeding location. A community of microorganisms eventually develops in the water at the base of the pitchers. These microorganisms live on the nutrients of the decaying insects, and may actually increase the nutrients available to the plant by further digesting its prey. The microorganisms are themselves prey to at least two species of carnivorous insects – the larvae of a mosquito and the larvae of a midge – which complete their life cycles in the pitchers. For some reason, the digestive enzymes secreted by the plant affect neither species.
(quoted from USDA site)