Which animal that lives in another animal or plant and eats the animal or plant without killing it?

Well, if you mean animals that eat both plants and meat, you are thinking of an omnivore, although parasites feed off animals and plants without killing them. Leeches are wll known for sucking blood without killing the creature they feed off fof, and also tape worms etc, although they can cause people or animals to starve. Hope I helped :)

-Hannah