Termites can be divided into three main types: subterranean, drywood and dampwood. These species will do the most damage to your home, but their behavior differs in a number of ways.
Subterranean termites are the most common termites in the U.S. They build their nests underground and create tubes of mud to access their food source. They also can tunnel up straight from underground if there is wood contact with the soil. Subterranean termites prefer springwood to hardwood, as hardwood is difficult for them to digest. The damage that they cause usually appears in layers. These chambers they create are called galleries. Often you can find soil in the galleries of subterranean termites.
Drywood termites don't need the soil to create their colonies. They prefer nesting in dry wood with low moisture content. Typically, this is interior wood, such as furniture. They eat the wood across the grain and create galleries within the interior of the wood they are feeding on. The walls of the galleries are very smooth and there is never soil present. Fecal pellets and shed wings are found outside the termite colony as debris, and can be a sign of infestation.
Dampwood termites prefer high moisture content in the wood they consume and live in. This is usually found outdoors as rotting wood on the exterior of your home. Their colonies are similar to the drywood termites, however, they will eat spring and summer wood. Their colonies also can contain the fecal pellets, which they sometimes don't expel. These pellets attach to the walls and create a bumpy surface.
The ecological significance of termites is great when it comes to managing debris. Termites eat dead and dying wood and help keep waste under control. When they turn to your home as a food source, however, that can be costly.