inquiline

An animal that lives commensally in the nest, burrow, gall, or dwelling place of an animal of another species.

The other study[…]involved the larvae of the caterpillar Maculinea rebeli, an inquiline of Myrmica schenki.

Queens of socially parasitic inquiline ants reproduce by laying eggs in the colonies of other species.

An organism that lives within a reservoir of water collected in the hollow of a plant stem or leaf.

Captured prey also constitute the resource base for a community of inquiline bacteria, protozoa, and invertebrates that inhabit the water-filled pitchers. For at least two of these inquilines (the pitcher-plant mosquito Wyeomyia smithii Coquillet and the pitcher-plant midge Metriocnemus knabi Coquillet) the availability of captured prey limits individual growth, and ultimately population growth[…]

The insect and other animal inhabitants of the pitchers, known collectively as the inquilines, may benefit the plants by breaking down prey and making nutrients available for plant absorption.