There the grown serpent lies; the worm that’s fled
Hath nature that in time will venom breed,
No teeth for the present.
– William Shakespeare
Macbeth, Act 3, Scene 4. Macbeth has just learned that Banquo has been murdered but his son Fleance escaped. Using metaphors to compare Banquo to a snake and Fleance to a worm, Macbeth comments that the son will in time grow into as big a threat to him as his father.