Drywood vs subterranean termites: how to tell the difference
Both are common in the San Fernando Valley, but they live differently, leave different clues, and are treated differently.
Updated October 2026.
Quick comparison
| Feature | Drywood termites | Subterranean termites |
|---|---|---|
| Where the colony lives | Inside the wood itself | In the soil |
| Typical evidence | Piles of tiny hard pellets below small holes | Mud tubes on foundations; damaged wood packed with soil |
| Where to look | Eaves, attic framing, window and door trim, furniture | Foundation, crawlspace, wood touching soil, fence posts |
| Swarm timing (SoCal) | Often late summer through fall | Often spring days after rain |
| Common treatments | Local treatment or whole-structure fumigation | Soil treatment or monitored bait stations |
Reading the clues
Pellets (frass). Drywood termites push their droppings out of small "kick-out" holes. They look like tiny grains of sand or coffee grounds, each with six concave sides under a magnifier. Fresh piles that come back after you sweep them up point to active drywood termites.
Mud tubes. Subterranean termites need moisture and build pencil-width tubes of soil and saliva to travel from the ground to wood. Break a tube open: live termites inside, or a tube rebuilt within days, means active infestation.
Swarmers and wings. Both types swarm. Piles of discarded wings near windowsills and light fixtures tell you a colony is nearby but not which type. Save a few swarmers in a sealed bag for the inspector.
Why identification matters
Fumigation addresses drywood termites throughout the structure but does nothing to subterranean colonies in the soil, and soil treatment doesn't reach drywood colonies in the attic. A licensed inspector (Branch 3, verifiable at pestboard.ca.gov) will identify the species and mark the findings on a diagram.
Reduce your risk
- Keep wood-to-soil contact to a minimum: fence posts, planter boxes and siding should not touch soil.
- Fix leaks and keep sprinklers from soaking the foundation.
- Paint or seal exposed wood such as eaves and fascia, and keep attic vents screened.