Scientific Name: Reticulitermes hesperus | Reviewed by The PCC Research Team
The Western Subterranean Termite is the most common and destructive termite species in California. Unlike Drywood termites that fly directly onto your roof, Subterranean termites attack your home from the ground up, quietly chewing through the framing from beneath your foundation.
Because they live deep underground in massive colonies of up to 100,000 bugs, they are incredibly difficult to detect until severe damage has already occurred. Understanding their unique biological need for soil moisture is the key to identifying and killing them.
The “Cliff Notes”: Key Takeaways
- The Dirt Connection: They must maintain physical contact with the soil to survive. They use mud tubes to cross concrete foundations to reach the wood of your house.
- No Sawdust: Unlike Drywood termites, they do not leave neat piles of frass. They pack their feces and dirt into the walls to insulate their tunnels.
- Spring Swarmers: They swarm during the daytime, typically on warm, sunny mornings immediately following a heavy California spring rain.
- The Cure: Liquid soil trenching (Termidor) or in-ground bait stations (Sentricon). Tenting a house will not kill them.
Biology: The “Thin Skin” Weakness
Why do Subterranean termites live in the dirt, while Drywood termites live in the attic?
The answer is in their exoskeleton. Western Subterranean worker termites are pale, creamy-white, and have incredibly thin cuticles (skin) that lack the waxy, water-retaining coating found on other insects. If a Subterranean worker is exposed to the dry, open air of California, it will rapidly lose moisture, dehydrate, and die within hours.
To survive, they must live in the damp, temperature-controlled soil deep underground. When they travel upward to eat the wood framing of your house, they build “Mud Tubes” (made of saliva, dirt, and feces) over the concrete foundation. These tubes act like a pressurized, climate-controlled highway, protecting them from the sun and dry air while they commute to work.
A massive, expensive mistake homeowners make is paying $3,000 to tent their house for Subterranean termites. Fumigation (Vikane gas) only kills bugs above the ground inside the wood. It does not penetrate the soil. As soon as the tent comes off, the Queen living 5 feet under your yard simply sends a new wave of workers up the mud tubes to continue eating your house. You must properly identify the species before signing a contract.
The “Along the Grain” Damage Pattern
If you break open a piece of damaged wood, you can easily tell which species caused the destruction.
Western Subterranean termites are picky eaters. When they attack a piece of structural lumber, they only chew through the soft “spring wood,” leaving the harder “summer wood” intact. This creates a distinct, layered, honeycomb-like pattern, with damage running strictly along the grain of the wood.
Furthermore, because they need to retain moisture, they will pack these hollowed-out galleries full of dried mud and soil brought up from the ground. Wood damaged by Subterranean termites often looks blistered or warped, frequently mimicking water damage.
The Spring Swarm
While Drywood termites usually swarm in the late summer/fall, Western Subterranean termites are spring swarmers.
Between March and May, especially on a bright, sunny day immediately following a heavy spring rain, the mature underground colony will release thousands of flying reproductives (swarmers). Subterranean swarmers are entirely black with four translucent wings of equal length.
- Read our Swarmer Identification Guide to learn the difference between flying termites and flying ants.
Eradication: Cutting the Soil Connection
Because the Queen is hidden safely underground, spot treatments (like Orange Oil) or tent fumigations will fail. You must establish a barrier between the soil and the home.
1. Liquid Soil Trenching (Termidor)
An exterminator digs a shallow trench around your entire foundation and pumps hundreds of gallons of a non-repellent liquid termiticide (like Fipronil) into the dirt. When the termites walk through the invisible barrier, they carry the poison back down to the Queen. Read our Trenching Guide here.
2. In-Ground Bait Stations (Sentricon)
Instead of pumping liquid chemicals into the earth, exterminators install green plastic bait stations around the perimeter of the home. The cellulose bait contains a chemical that prevents the termites from molting, causing the entire colony to slowly collapse from the inside out.
Get a Soil Treatment Quote
Because Subterranean termite treatments require digging trenches or drilling through concrete patios, prices vary wildly based on your home’s footprint. Contact a licensed California structural pest control operator to measure your property.
Call For Trenching Quotes: (866) 204-1751Frequently Asked Questions
Q: Why do I have Subterranean termites if my house is built on a concrete slab?
A: Termites only need a gap of 1/32 of an inch to enter a home. In slab-foundation homes, they easily squeeze through the expansion joints in the garage, the tiny gaps where plumbing pipes penetrate the concrete, or simple stress cracks in the slab.
Q: Will removing mulch from my foundation stop them?
A: It won’t stop an active infestation, but pulling thick wood mulch and wet soil away from your home’s siding is the #1 preventative measure you can take. Subterranean termites thrive in moist, earth-to-wood contact zones.
Q: If I break their mud tubes, will they die?
A: No. While breaking the tube exposes the few workers currently inside to dry air, the millions of termites underground are safe. They will simply rebuild the mud tube overnight, often taking a slightly different path.