This discovery has a spy-movie-like plot. Enemies live among the hosts unidentified and feast on them later! Such is the case with beetles that belong to the Staphylinidae and are called rove beetles. Their hosts are army ants.
Across the tropical forest floor are several army ant colonies. The ant-mimicking beetles look like ants, smell like ants, March with ants, and even groom the ants. They do all this with excellent deception. Vivid changes in body shape and behaviour fools the ants into accepting these beetles. Rove beetles have glands that secrete defensive chemicals that help them to survive among the army ants without the ants wanting to devour the beetles. This is how these beetles evolve into army ant parasites and later feed on them.
This phenomenon has occurred multiple times in the history of evolution in these beetles. The interesting part is that rove beetles and army ants are not even close relatives. Their last common ancestor lived 105 million years ago!