AntsCanada (previously) has an overpopulation problem in his yellow crazy ant colony, so he added two kinds of carnivorous pitcher plants. The resulting relationship between ant versus plant turned out to be quite fascinating.
Via Science Daily wild pitcher plants often have ant species that work with them to maintain their health via symbiosis:
The unusual relationship between insect-eating pitcher plants and ants that live exclusively on them has long puzzled scientists. The Camponotus schmitzi ants live only on one species of Bornean pitcher plants (Nepenthes bicalcarata), where they walk across slippery pitcher traps, swim and dive in the plant's digestive fluids and consume nectar and prey that fall into the trap. Though the benefits to the ants are obvious, it has been harder to tell what exactly the plants gain. However, plants that harbor the insects grow larger than those that do not, suggesting a mutualistic relationship exists between the two.