Wood is a biological material. If protected from moisture and insect attack, it can last for centuries. When wood is not properly protected, however, it will succumb to biological processes that decompose wood: insects that eat the wood or fungi that cause rot and decay. The most damaging insects that attack structural wood are termites. Their activity results in damage and control costs that exceed $1.5 billion per year nationally. Beetles are the next important group of insects that attack wood, while bees, wasps and ants are third in importance, depending on geographical location. Wood-inhabiting fungi are another group of organisms that occasionally cause problems.