We have many problems with rot and wood destroying insects in this region. A few months back, I was inspecting an older house that had a number of issues with wood destroying organisms. Since many of the insect pests are attracted to wet and decayed wood, it is common to find wood destroying insects living in rotten and wet wood.
At this particular crawl space, the first thing that I noticed, when opening the hatch, was frass or shavings from carpenter ants.
Honestly, that was no big surprise, since I had previously seen the little devils crawling around at the perimeter of the house.
In addition to the carpenter ants, once down inside the crawl space, there was an ongoing infestation of wood boring beetles -- the anobiid beetle that is so common here in the northwest. The pest leaves tiny shot-sized exit holes and causes massive damage to the afflicted lumber.
The problems at this home were, in part, caused by high moisture levels in the crawl space, the result of a missing vapor barrier over the earthen floor. The solution to the infestation, which can be expensive to repair, is to have a contractor come in and locate all of the structurally damaged wood. Rebuild the substructure in a professional manner and eliminate the conditions that were conducive to creating the problem in the first place. Finally, have a licensed pest control operator apply a chemical treatment that will control the wood destroying insects.