Domatium

A domatium (plural: domatia, from the Latin "domus", meaning home) is a tiny chamber produced by plants that houses arthropods.

Ideally domatia differ from galls in that they are produced by the plant rather than being induced by their inhabitants, but the distinction is not sharp; the development of many types of domatia is influenced and promoted by the inhabitants. Most domatia are inhabited either by mites or ants, in what can be a mutualist relationship, but other arthropods such as thrips may take parasitic advantage of the protection offered by this structure.