Drywood vs. Subterranean Termites | Fresno Termite Control

One question, two completely different problems

“I have termites” is only half a diagnosis. Fresno houses host two different insects under that name, and they have less in common than their shared name suggests: they live in different places, leave different evidence, and fail under different attacks. Everything that matters comes after you know which one you have. Drywood treatment happens in the wood itself, subterranean treatment happens at the soil, and neither method touches the other termite at all. Buy the wrong one and the colony keeps eating while the receipt ages.

That’s not a hypothetical. Tent jobs get sold for mud-tube problems, and soil treatments get pitched at drywood infestations, sometimes through error and sometimes through whatever the seller had on the truck. Either mistake runs to real money: a fumigation that didn’t touch the soil colony, or a trench-and-treat around a house whose actual problem is sealed in an attic rafter. The defense is cheap: learn the evidence, which is unambiguous most of the time, and make any recommendation explain itself against what was actually found. This guide covers the two species in depth; the broader signs guide covers the full evidence checklist if you’re starting from “I found something weird.”

The identification table

Where the colony lives

Drywood termites: Entirely inside the wood
Subterranean termites: In the soil, commuting to the wood

Signature evidence

Drywood termites: Frass pellets below kick-out holes
Subterranean termites: Mud tubes on foundations and piers

Swarm timing here

Drywood termites: Hot, still late-summer afternoons
Subterranean termites: After the first fall rains

How they're treated

Drywood termites: In the wood: local, heat, or tent
Subterranean termites: At the soil: barrier or baiting

What to compare	Drywood termites	Subterranean termites
Where the colony lives	Entirely inside the wood	In the soil, commuting to the wood
Signature evidence	Frass pellets below kick-out holes	Mud tubes on foundations and piers
Swarm timing here	Hot, still late-summer afternoons	After the first fall rains
How they're treated	In the wood: local, heat, or tent	At the soil: barrier or baiting

Mud tubes built by subterranean termites on a concrete foundation

Close-up of worker termites in exposed wood

Drywood termites: the colony inside the board

A drywood colony needs no soil, no moisture source, and no contact with the ground. The whole operation (king, queen, and a few thousand workers) lives inside the piece of wood it’s eating, extracting the water it needs from the wood itself. That self-sufficiency is why drywood termites turn up in attic rafters, fascia boards, window frames, garage framing, and even furniture, and why an infested antique can seed a house that never had a termite problem.

Because the colony is sealed inside, the evidence is what escapes. Drywood termites keep their galleries clean by pushing droppings out through pinhole-sized kick-out holes, and those droppings, called frass, pile up below: dry, hard, six-sided pellets like coarse pepper. Find fresh frass and you’ve found an active gallery within a few feet. The flip side of their self-sufficiency is pace. A drywood colony numbers in the thousands rather than the hundreds of thousands, so the damage accumulates slowly, board by board, which buys homeowners time if the evidence gets read early. No-tent local treatment handles the confined cases; spread-out infestations push toward whole-structure methods, and that decision gets its own guide.

Still not sure which you have? The free inspection answers it with evidence.

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Subterranean termites: the colony under the yard

The western subterranean termite is Fresno’s dominant species by a wide margin, and its operation is the inverse of drywood’s. The colony lives in the ground, where the moisture is, and can number in the hundreds of thousands. Workers tunnel out through the soil, and when they have to cross open air to reach wood, they build the mud tubes that give them away: covered soil highways up stem walls, piers, and plumbing penetrations. Break one open and live workers mean an active commute.

Moisture dependence is their defining trait, and in Fresno we hand it to them. A climate that should bake the ground dry all summer instead keeps it damp wherever lawns and drip lines run against foundations, which is why subterranean pressure here is steady rather than seasonal. They’re also the bigger structural threat: a large soil colony feeding on sill plates and floor framing removes far more wood per year than a typical drywood colony sealed in one board.

Swarm timing separates the species too. Subterranean swarmers fly on warm days after the first soaking fall rains, occasionally again in spring; drywood swarmers pick hot, still afternoons in late summer. Either way, treatment happens where the colony is — at the soil for this one, never in the wood alone.

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