The signs are completely different — and so are the treatments. Here's how to tell drywood and subterranean termites apart, and why it matters before you spend a dollar on treatment.
Why Identification Comes Before Treatment — Every Time
Getting the wrong treatment for termites doesn't just fail to solve the problem — it wastes the full cost of treatment. Fumigation is highly effective against drywood termites but has zero effect on subterranean termites. Termidor soil barrier eliminates subterranean colonies but doesn't touch drywood termites living in above-ground wood.
Before you spend a dollar on any termite treatment, you must correctly identify the species. This is why professional inspection — not YouTube diagnosis — should always be step one.
How to Identify Drywood Termites
Drywood termites (Incisitermes minor and Cryptotermes species) live entirely within the wood they eat. They have no soil contact and get moisture from the wood itself. They're the most common termite threat in Southern California.
Primary signs of drywood termites:
- Frass — the most reliable indicator. Drywood termites push excrement out of small kickout holes. Frass is hexagonal (6-sided), sand-like pellets, typically cream to dark brown in color. You'll find piles on surfaces below infested wood — windowsills, floors, or countertops.
- Kickout holes — tiny circular holes (about 1–2mm) in wood surfaces where termites push out frass. Common in eaves, fascia boards, window frames, and hardwood floors.
- Swarmers found indoors in late summer/fall — winged reproductives emerge August–November, typically in the afternoon. Finding discarded wings near windows is a strong indicator.
- No soil contact needed — if the infestation is in attic framing, second-floor walls, or furniture, it's almost certainly drywood.
- Hollow sound when knocking on infested wood — the interior galleries create a distinctive hollow resonance.
How to Identify Subterranean Termites
Subterranean termites (Reticulitermes hesperus is the most common California species) live in underground colonies and require moisture and soil contact. They're the most destructive species in the US.
Primary signs of subterranean termites:
- Mud tubes — the clearest indicator. Pencil-width tunnels of soil, mud, and termite secretions running from soil level up foundation walls, piers, pipes, or any path from soil to wood. Finding mud tubes is essentially a confirmed subterranean infestation.
- Damaged floor joists — subterranean termites consume wood along the grain, leaving a honeycomb-like structure. Floor joists in crawlspaces are a common target.
- Swarmers from soil in spring after rain — pale yellow, small (about ¼ inch), equal-length wings. Found near soil entry points rather than inside the home.
- Spongy or bouncy floors — especially near bathrooms or kitchens where subfloor moisture is higher.
- Require soil contact — if the infestation is on the ground floor, near bathrooms or kitchen, or in the subfloor, suspect subterranean.
Side-by-Side Comparison
| Feature | Drywood Termites | Subterranean Termites |
|---|---|---|
| Colony location | Inside the wood | Underground |
| Soil contact required | No | Yes |
| Primary evidence | Frass + kickout holes | Mud tubes |
| Swarming season | Aug–Nov (afternoon) | Feb–May (after rain) |
| Swarmer color | Dark brown/black | Pale yellow |
| Damage pattern | Across wood grain, smooth galleries | Along grain, honeycomb |
| Effective treatment | Fumigation, heat, orange oil | Termidor soil barrier |
| Does NOT respond to | Termidor | Fumigation |
What Happens When You Treat the Wrong Species
This scenario happens more often than it should: a homeowner sees termite activity, calls a pest company, and the company recommends — or the homeowner requests — a treatment without proper identification. One common example:
A homeowner finds frass piles (strongly indicating drywood) and requests Termidor treatment at $1,200 because it's cheaper than fumigation. Termidor is applied to the foundation perimeter. Result: zero effect. Drywood termites in the attic framing have no exposure to the soil barrier and continue feeding. A year later, the same homeowner pays $1,800 for fumigation anyway — having already spent $1,200 on an ineffective treatment.
The reverse also happens: fumigation ordered for what turns out to be subterranean-only activity. Effective for eliminating any drywood present, but the subterranean colony in the soil remains intact. Mud tubes reappear within weeks.
The Inspection Is the Starting Point
A licensed inspector who physically examines the property can differentiate the two species from physical evidence in under 30 minutes. Attempting to self-diagnose based on photos or descriptions risks a costly error. Our free inspection includes species identification as the first step before any treatment recommendation.
Related: Drywood Termites · Subterranean Termites · Tent Fumigation · Termidor Treatment