inquiline
From ZooTerms (Dictionary of Invertebrate Zoology)
inquiline (noun; Latin inquilinus, tenant): 1. A commensal organism that lives habitually on or within the body of another, or in its nest or abode without benefit or damage to either; a guest. See also inquilinism.
2. An animal that lives in the home of another species and derives a share of its food
See also: inquilinism. 3. An insect developing inside a gall produced by another species.
