A few things to consider Wigwam:
Have you carried any old or damp wood indoors recently? - a load of them could have fallen off.
They feed on rotting wood - so check for damp in door surrounds etc as this may be a problem anyway.
Check for holes where they may be getting in (and out - because they won't last long in a warm dry house) and use either ant powder or the smellier but more effective solution, creosote.
(by the way, am assuming that this is an indoor problem)