Timber that does not sound right
Tap along skirting boards, posts and frames. A hollow or papery sound can indicate that the inside has been consumed, even where the surface still looks intact.
Trails, mud and blistered paint
Look for narrow mud-like lines running over walls, foundations or posts, and for paint or plaster that has blistered or cracked along a timber edge.
Wings and small pellets
After a swarm, discarded wings collect near door frames and windows. Small pellet-like material near skirting boards may also be a sign worth investigating.