They were after wood (carpenter ants). They ate the deck and some of the support structure. They like damp wood.<p>The solution was:<p>1. get rid of all rotting wood near the house
2. make the deck out of concrete and iron
3. make sure no vegetation touches the house
4. roof overhangs that keep the exterior wood dry<p>and lastly, just to be sure, the bug guy comes and sprays a Line of Death around the perimeter once a month :-)<p>The idea is to not create an environment that is attractive to pests. For example, I also had a yellowjacket problem. I eventually was told that they loved cedar shingles. Replaced the shingles with asphalt ones, and no more yellowjackets.