CHIZPURFLE

"Chizpurfles are small parasites up to a twentieth of an inch high, crablike in appearance, with large fangs. They are attracted by magic and may infest the fur and feathers of such creatures as Crups and Augureys. They will also enter wizard dwellings and attack magical objects such as wands, gradually gnawing their way through to the magical core, or else settle in dirty cauldrons, where they will gorge upon any lingering drops of potions."

-J.K. Rowling