Pitcher plants produce sweet nectar to lure insects in their
deadly traps - this is what can be read about Nepenthes. But
there is much more in it than a green robber catching animals.
It seems to be true for the solitary insects, for moth, flies or beetles.
But the relationship between ants and pitcher plants is a very
special and for more interesting one.
As other insects ants are attracted by the nectar produced
by the plants. Searching for the nectar they climb the plant, and if
successful they go back to the nest to alarm their sister workers. (Having
a perfect working trap would be of a massive disadvantage for the plant.
It would catch one ant when it could attract lots of them.) But ants do
not only collect nectar, and here begins the more interesting part. While
adult animals need the sugar as "fuel" the larvae need protein
to grow. Depending on the species this can be e.g. fungae or other insects.
Many other plants use this to get protection against herbivores. They produce
nectar, and the ants who collect it also collect other prey on the plant,
cleaning it while doing so. This phenomenon is called myrmecophily.
On Nepenthes ants do the same, and this seems to be the reason why
the pitcher plants offern nectar not only on the peristome but also on other
parts, especially the young, develloping leafs and pitchers.
Nepenthes bicalcarata goes one step beyond this. It is usually living
with its own ants, and the ant species Camponotus schmitzi can only be
found nesting in this pitcher plant species. The plant offers "her"
ant not only nectar but also nesting space. The tendrils of the pitchers are
hollow and swollen.
Many other plants produce similar domatia in leaves, stems or other parts.
Most of them have their specialized ant species, and most of them can not survive
without this protection.
N. bicalcarata is not depending on its ant.