Term:

Domatium (pl. domatia)
Definition:

A cavity or chamber, mostly associated with leaves, that usually serves as home for ants or mites.
Notes:

In Lecythidaceae, a few species of Cariniana, such as C. domestica, C. micrantha, C. pyriformis, and C. rubra have domatia in the axils of their secondary veins. Species of Coroupita also have them in the axils of secondary veins but the domatia in the species of this genus are axillary tufts of hairs.