Pitcher plants are well known for ‘tricking’ insects into plunging to their death. One particular pitcher plant, Nepenthes bicalcarata not only have the usual device to get insects into falling to their death, they have an additional helper – ants (Camponotus schmitzi) that help them to capture more prey while preventing thieves from stealing nutrients from them!
Ants clean the surface for insects to fall in
These ants nests in the swollen, hollow part of the pitcher tendrils. They got housing with ‘rent’ from their pitcher plant landlord. And the way that the ants pay their rent is by cleaning the part of the pitcher plant (called peristome) that cause the unknowing prey to slide into the pitcher cup.
When they are no ants renters, this part of the pitcher plant is easily contaminated with fungal and other microscopic growth. When the right ants are present, the pitcher has a higher capture rate due to a nice, clean and smooth surface for insects to fall into the cup. The long-term benefit – pitcher plants with the right ants’ renters live longer!
But this is not enough rent. The ants needed to do more!
Ants swim in pitcher cup to hunt nutrients’ thieves
Not all insects that fall into the cup end up to be food for the pitcher plants. Some mosquito larvae have adapted to live in the digestive juice of the pitcher cup and STEAL the nutrients that are meant for pitcher plants.
So the ants were recruited to help hunting down these nutrient thieves. Normally ants cannot swim, let alone dive. To be able to catch the nutrient thieves, these ants swim and dive in the pitcher plant digestive fluids hunting down mosquito larvae and chopping them into pieces.
In return for such a good service, the ants got to consume some of the prey that was in the pitcher cup. A win-win situation indeed.
Thornham DG, Smith JM, Grafe TU, Federle W (2011) Setting the trap: cleaning behaviour of Camponotus schmitzi ants increases long-term capture efficiency of their pitcher plant host, Nepenthes bicalcarata. Functional Ecology 26: 11-19.
Scharmann M, Thornham DG, Grafe TU, Federle W (2013) A novel type of nutritional ant-plant interaction: ant-partners of carnivorous pitcher plants prevent nutrient export by dipteran pitcher infauna. PLoS ONE 8(5):e63556. doi:10.1371/journal.pone.0063556