There are several insect species that feed on or otherwise damage sound, healthy wood, including termites, carpenter ants and carpenter bees. When wood is damaged or wet, it may be susceptible to attack by other bugs and fungi.
Termites are a well-known household pest that can cause major structural damage to buildings, but they aren't the only wood-boring pests that can cause dangerous structural deficiencies. Because there are relatively few wood-damaging insects, it can be easy to identify these pests by location. For example, carpenter ants tend to be found in cooler climates, while powderpost beetles thrive in structural wooden beams only in damp, coastal areas, though they can be found in hardwood furniture in any climate.