an animal that uses or lives habitually in the home of some other species, as does the cuckoo, for example, which lays its eggs in other birds’ nests
inquilinism /inʹkwiliniz(ə)m/ noun
inquilinous /-ʹlienəs/ adj
[Latin inquilinus tenant, lodger, from in-2 + colere to cultivate, dwell]