Number twelve, Grimmauld Place has an infestation of Doxys. Doxys can be removed by using Doxycide, a liquid that causes the creatures to become immobile. If bitten by their poisonous teeth, the antidote should be taken immediately.
The occupants of Grimmauld Place spend time trying to get rid of the Doxys in the drawing room. Fred and George Weasley secretly keep some of the unconscious Doxys from Grimmauld Place, hoping to experiment with the venom for their new joke product, Skiving Snackboxes.