There are more than 600 species of plants worldwide known to capture small animals to obtain extra nutrition. One species in the tropical peat swamp forests of Borneo, the fanged pitcher plant, Nepenthes bicalcarata, not only traps insects, but also provides a home for the highly specialised species of carpenter ant, Camponotus schmitzi.
The plant's leaves are specially modified as cup-shaped insect traps. These pitchers produce sweet nectar to lure insects; slippery surfaces on the upper rim of the pitcher cause them to slide and fall into the pitchers where they are held and digested by the fluid within. Amazingly, the resident Camponotus schmitzi ants appear to be completely immune to the traps; they nest inside hollow stems of the plant, feed on the traps' nectar without falling and "steal" prey from the pitchers by swimming and diving in the digestive fluid.
Many "ant-plants" have evolved close relationships with ants, which can provide protection from leaf-feeding insects and fungal attack, in return for nesting space and food rewards. The fanged pitcher plant is the only known insect-eating ant-plant. Despite a number of studies since its discovery in the late 19th century, it has been unclear what, if anything, the plant gains from the association.
We discovered that the Camponotus schmitzi ants thoroughly clean the slippery trapping surface of their host plant. Even when strongly contaminated by cornflour, the ants' cleaning restored the slipperiness of the trap within a few days. By cleaning the slippery trap, the ants ensure it is maintained in good condition and can continue to capture insects for much longer than if the ants are absent. Indeed, the pitchers of Nepenthes bicalcarata can live and remain active three times longer than pitchers from other Nepenthes species in the area. So, by maintaining the traps of the plant, the ants do more than just clean: they help the plant to be well-fed.
Source: http://www.functionalecology.org
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