How do some Melastomataceae plants benefit from providing shelters for ants?

In some members of the Melastomataceae family, such as Maieta, Tococa, and certain Clidemia species, the plants develop saclike outgrowths at the base of their leaves that serve as shelters for ants.1

These ants enter the shelters through small holes on the lower surface of the leaves. By inhabiting these structures, the ants provide a defensive benefit to the plant by protecting the leaves from herbivores, such as caterpillars, which the ants kill or drive away. This relationship is a form of defensive mutualism, where the plant provides housing in exchange for protection against herbivory.12