These are small termites. The winged form is approximately 3/8 inch (8-9 mm) long including the wings. They are dark brown to brownish black with brownish gray wings. The soldiers have a cream-colored head with black jaws and a grayish white body. They are approximately ¼ inch (6 mm) long. Nearly half their length is head and jaws. The "worker" caste is grayish white and about 3/16 inch (5 mm) long. They live in the soil in nests which may originate in buried stumps or logs that may be as deep as 10-20 feet (3-6m).

Since subterranean termites live in and obtain their moisture from the soil, damp wood is not essential for attack. This makes any wood structure a potential site for subterranean termite feeding. The most frequent type of infestation is in buildings constructed near or on pre-existing nests. Cement slab foundations are no deterrent since eventual frost cracks, cold joints between slab and foundation walls, and areas around plumbing provide easy entry for these termites.

Indications of subterranean termite infestation are swarming behavior, damage signs, the distinctive tapping sounds that the soldiers make when disturbed, and especially by the presence of shelter "mud" tubes. These are often found on the foundation walls or in cracks. Occasionally they may be suspended from soil to subflooring. The tubes provide protection from natural enemies. Although clearly diagnostic of subterranean termites, tubes are not always present. Fecal pellets of subterranean termites are often clumped in the galleries or incorporated into the shelter tubes and feeding areas of the wood and rarely are loosely scattered as with dampwood termites. Fecal material packed in the galleries of the wood appear to be "scaly" and offer a distinctive clue like that of subterranean termites rather than some other woodeating pest - even in the absence of this termite. Mature colonies swarm annually, while colonies from a primary pair may not produce swarms for several years. They may swarm at any time of the year, depending on climatic conditions. In eastern Washington, swarming is predominantly in the spring, while in western Washington, swarming is predominantly in the fall.

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Pacific Dampwood

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Western Subterranean

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Subterranean Termite Tubing