Subterranean Termite: Signs, Mud Tubes and Treatment

Quick answer

A subterranean termite is a termite that lives in a colony in the soil and travels to wood above ground through tunnels and mud tubes, eating the wood from the inside while staying hidden.

It is the most common termite in most of the United States. Colonies need moist soil, can hold hundreds of thousands or even millions of termites, and are treated with soil barriers or baits, not tent fumigation.

Quick facts

The key facts about Subterranean Termite, with sources:

Main U.S. genera: Reticulitermes (native), Coptotermes (Formosan), Heterotermes (desert Southwest) ²
Most common type: The native subterranean termite, in most of the U.S. ¹
Colony size: Hundreds of thousands to several million termites ²³
Worker size: About 1/4 inch, cream-colored and eyeless ³
Moisture need: High; usually keeps a link to the soil ²
Best-known sign: Mud (shelter) tubes about 1/4 inch wide on foundations or wood ³
Treatments that do not work in buildings: Fumigation, heat, freezing, electrocution ²

Key takeaways

Subterranean termites live underground and come up into a house through mud tubes, cracks and wood that touches soil.
They need moisture, so wet soil, leaks and wood near the ground raise the risk.
Swarmers inside the house, mud tubes and hollow wood are the main signs.
Tent fumigation does not control them; soil-applied termiticides and baits do.
One colony can feed on many spots more than 200 feet apart, so spraying one board fixes nothing.

A soil-dwelling wood eater, explained simply

Think of a subterranean termite colony as a city under your yard. The termites live in the soil, where it is damp and dark.

They send workers out through tunnels to find wood, which they eat for its cellulose (the tough fiber in plants).

When the wood is above ground, such as a sill plate or floor joist, they build tubes of mud to reach it without drying out.

In science terms, these are social insects with three main castes. Workers do the feeding and building. Soldiers guard the colony with large jaws. Reproductives (kings, queens and, once a year, winged swarmers) make more termites ³.

The EPA says the native subterranean termite is the most common type in most of the country. Drywood termites and the invasive Formosan termite are less common ¹. Termites as a group cause billions of dollars in structural damage each year ¹.

Workers are about 1/4 inch long, soft, cream-colored and blind ³. People rarely see them because they stay inside soil, tubes and wood. That is why many owners first learn about termites from a swarm or from damage found during a remodel ¹.

Not the same as drywood termites

Subterranean termites nest in soil and need moisture. Drywood termites live entirely inside dry wood with no soil contact and leave six-sided droppings. The two are treated in very different ways ².

How a subterranean termite colony finds and eats a house

The colony follows the same pattern whether it is eating a fallen log or a floor joist.

Start small. A new king and queen dig into soil near wood. UC IPM notes a colony may have only about 75 members after its first year ².
Grow for years. Over several years the colony grows to hundreds of thousands of termites ². University of Maryland Extension says some reach several million ³.
Forage underground. Workers tunnel out to food. One colony can use food sources more than 200 feet apart ³.
Build mud tubes. To cross concrete or reach wood above the soil, workers build tubes from soil, saliva and bits of wood or drywall ².
Eat along the grain. They hollow out the softer wood and leave the harder layers, so the surface can look fine while the inside is thin ².
Swarm. A mature colony sends out winged swarmers once a year to start new colonies ⁴.

Process From soil nest to damaged wood

Soil nestDamp, dark, protected colony center
Underground tunnelsForaging reach can exceed 200 feet
Mud tubeSoil and saliva bridge over concrete
Structural woodSill plates, joists, framing
Hollow galleriesSoft wood eaten, hard layers left

The colony stays connected to soil moisture, which is why breaking the soil link is the basis of most treatments. Source: [2] [3]

Activity follows the seasons, though not neatly. In California, UC IPM reports foraging is minimal from November to February and highest in summer, with erratic swings in between ².

Main subterranean termite species in the U.S.

Swarm timing varies by species and region; local extension offices publish the dates for your area.
Species	Where it is found	Swarming	Notes
Eastern subterranean termite (Reticulitermes flavipes)	Most widely spread across the eastern U.S. ⁵	February to April in Mississippi ⁴	Dark swarmers; most common house-infesting termite in much of the East
Western subterranean termite (Reticulitermes spp.)	California and the West ²	Afternoons in spring or fall, often after rain ²	Most common and destructive type in California ²
Formosan subterranean termite (Coptotermes formosanus)	Hawaii, the Southeast, north to Virginia, inland to Tennessee, and southern California ⁵	May to June in Mississippi; at dusk, drawn to lights ⁴²	Soldiers are 10–15% of the colony vs 1–2% in native colonies ⁵
Desert subterranean termite (Heterotermes aureus)	Sonoran Desert, southeastern California ²	Late afternoon or early evening, July to September ²	Most destructive subterranean species in that desert ²

Formosan termites also build “carton” nests from soil, chewed wood and saliva inside walls or hollow trees ⁵. That lets a colony live above ground if it finds a steady water source, such as a roof leak.

Example: why one foraging colony reaches so much of a lot

This example uses only published figures to show the reach of one colony. It is an illustration, not a survey of any real home.

Input	Published figure	What it means for a house
Distance between food sources one colony uses	More than 200 feet ³	A colony nesting under the neighbor’s yard can still reach your sill plate
Formosan foraging range in the field	Up to 100 m (about 328 ft) ⁵	Invasive colonies reach even farther
Colonies under one house	A 2,400 sq ft footprint could sit over several colonies ²	Treating one spot may leave other colonies untouched
Width of a mud tube	About 1/4 inch ³	Easy to miss behind stored boxes or insulation
Time to swarm	Several years of colony growth ⁴	If swarmers appear indoors, the colony has been there a while

The point is scale. A pencil-width tube on one pier may be the only visible part of a colony spread under a whole yard. That is why pros treat the soil around the whole structure or use baits the colony shares, not a spray on one board.

Where the term shows up on paperwork

On a termite inspection report, look for “subterranean termites” with the evidence found: live termites, mud tubes, damage or swarmer wings, and where each was seen. A good report also lists “conducive conditions,” such as wood touching soil or a leak.

On a treatment proposal, the type matters. A subterranean plan names a liquid soil treatment, a bait system or both, plus the areas covered. A plan that offers tent fumigation for subterranean termites is a red flag, because UC IPM says fumigation does not work for them in structures ².

On a termite bond or warranty, the contract usually says which termites it covers. Many cover subterranean termites only. Our guide to termite warranties and bonds explains what to check.

On a product label, termiticides must carry directions to control termites and protect the structure. The EPA says a product without them should not be applied for that purpose ¹.

Warning signs of subterranean termites

These are the signs extension entomologists list. One sign is enough to call for an inspection.

Mud tubes on foundation walls, piers, exposed wood or even ceilings ³. Breaking one open may show live workers ².
Swarmers or piles of shed wings on floors, window sills or in spider webs ³.
Wood that sounds hollow or lets a screwdriver push through the thin surface ²¹.
Dark or blistered wood, or paint that bubbles and peels ³².
Soil packed into cracks and gaps where it should not be ³.
Sagging floors or new settling cracks, in later stages ³.

Do not tear into structure or spray swarmers

Spraying or vacuuming swarmers does not touch the colony feeding in the wood ⁴. Do not pull out load-bearing wood yourself. Many termiticides are highly toxic, and a bad barrier treatment can contaminate a home or a nearby well ¹. If a termiticide reaches a person, call Poison Help at 1-800-222-1222.

What each control approach does well

Strengths

Liquid soil treatment is the most common soil method. It puts a treated zone between the colony and the house ¹.
Baits use a slow-acting active ingredient that workers carry back and share ¹. UF reports chitin-synthesis-inhibitor baits kill workers as they molt, with full die-off in about 3 months ⁵.
Building fixes such as keeping wood 12 inches above soil cut the colony’s easy routes ².
Pre-construction options include treated soil under slabs, treated wood and borate wood sprays ¹.

Weak spots

Soil treatments may need trenching, drilling or rodding through slabs, which a pro must do ².
UC IPM says baits can take months or even years and need ongoing checks ².
A poorly done barrier can contaminate the home and wells and still fail to protect it ¹.
No method lasts forever. Homes with a history of termites should be inspected every few years ².

Why subterranean termites are hard to stop for good

The colony stays out of sight in the soil, often past your lot line, so success is judged by the lack of new activity, not by a dead nest.

Most yards are full of termite food. UC IPM points out that soil around a home usually holds buried roots, stumps or old fence posts, so swarmers in the yard do not prove the house is infested ². It also means new colonies can start nearby after a treatment.

Building details can hide them. Stucco or siding that runs into the soil lets termites travel unseen up to the wood ². Slabs, porches and additions create gaps that are hard to treat.

What drives the cost of subterranean termite work

We do not list prices here, because a fair figure needs many dated local quotes. The things that move a quote are steady, though.

The method matters most. A liquid soil treatment is priced on the linear feet of foundation and how much drilling through concrete it needs. A bait system adds monitoring visits over time.

The foundation type (slab, crawl space or basement), the size of the building, how much damage must be repaired and whether a warranty is included all change the total. Our termite treatment cost estimator shows how these factors combine.

Lifespan applies to the treatment, not the bug. Mississippi State Extension points readers to a table in its Publication 2765 on how long soil treatments last ⁴, and protection depends on the product label and soil conditions.

The University of Maryland suggests a contract with yearly inspection and re-treatment after an infestation ³. Get the length of coverage, and what voids it, in writing.

How a professional subterranean termite job usually runs

Inspection. UC IPM says a licensed pest management professional must inspect before any treatment ². The inspector maps tubes, damage and moisture problems.
Bids. University of Maryland Extension advises getting estimates from several companies and comparing plans, costs and warranties ³. The same source says you can take weeks or even a few months to weigh the problem, so there is no need to sign on the spot ³.
License check. Termite firms must be licensed by the state. The EPA says to ask to see the license ¹. Our license lookup tool points to each state’s search.
Treatment. The crew applies a soil treatment around and under the structure, installs bait stations, or both. Some jobs drill through slabs or porches.
Re-entry and records. The EPA says the applicator should tell you when it is safe to go back into treated areas ¹. Keep the service record and product name.
Repairs and follow-up. Fix the moisture problem and damaged wood. Bait systems get regular checks; soil jobs get yearly inspections if under contract.

Our termite control service page covers what a job includes. Structural repairs to load-bearing wood may need a contractor and a building permit.

What an owner can check and fix

Keep wood under the house at least 12 inches above the soil, per UC IPM ².
Grade soil so water drains away, and keep gutters and downspouts working ¹.
Fix leaks quickly and keep crawl space vents clear of plants ¹.
Seal cracks and utility openings in the foundation with cement, grout or caulk ¹.
Keep firewood, lumber and wood debris away from the house ¹.
Look over the foundation and crawl space once or twice a year for tubes or damage.

The 12-inch rule of thumb

UC IPM recommends keeping structural wood at least 12 inches above soil, or putting a 12-inch band of smooth concrete, coarse sand or other inorganic material between them ².

A yearly pest inspection adds a trained eye, and our pest risk checklist covers the moisture and wood-contact items to look at.

When to call a professional

Call when you find mud tubes, swarmers indoors, or soft or hollow wood. Mississippi State Extension says swarmers inside a building mean it is infested and needs professional treatment ⁴.

Call your current company first if you already have a termite contract ⁴. Call a structural contractor as well if floors sag or wood is badly damaged.

Do not buy a product that only says it “kills termites.” The EPA notes those products only kill termites they touch and do not protect the structure ¹.

Rules and standards that apply

Federal (EPA, FIFRA). The EPA registers termiticides under federal law. A product needs more than 100 studies and tests before registration ¹. Termiticide testing follows EPA Pesticide Registration Notice 96-7 and test guidelines OCSPP 810.3600 and 810.3800 ¹.

The label. Termite labels must include directions to control termites and protect the structure. Use outside the label is illegal. Most states also review labels ¹. Our pesticide safety guide explains labels and signal words.

State licensing. States license termite companies and applicators. In Maryland, for example, Extension says to confirm certification with the Maryland Department of Agriculture Pesticide Regulation Section ³. See our page on pest control licensing.

Complaints. To report a misapplication, contact your state pesticide agency or the National Pesticide Information Center at 1-800-858-7378 ¹.

Subterranean termite vs other wood pests

Feature	Subterranean termite	Drywood termite	Carpenter ant
Where the colony lives	In soil ²	Inside dry wood, no soil link ²	Outdoor parent nest plus indoor satellites ²
Main sign	Mud tubes ³	Six-sided fecal pellets ²	Fibrous sawdust (frass) ²
Gallery contents	Soil in galleries ³	Pellets, no soil ²	Clean, smooth tunnels, no soil ²
Eats wood?	Yes	Yes	No; it digs nests in wood ²
Tent fumigation used?	No; not effective ²	Yes, for widespread cases ²	No

Ant swarms are often mistaken for termites. The EPA notes ant front wings are longer than the hind wings and ant antennae bend at a right angle, while termite wings are about equal and antennae are straight ¹. Our pest identifier walks through the clues.

Common subterranean termite myths

Myth Swarmers in the yard mean my house is infested.: Reality Not on their own. UC IPM says most soil holds buried wood, so yard swarms are common. Swarmers indoors are the real alarm ²⁴.
Myth Tenting the house will kill them.: Reality Fumigation, heat, freezing and electrocution are not effective for subterranean termites in buildings ².
Myth A brick or concrete house is safe.: Reality Termites cross concrete in mud tubes and enter through cracks and utility gaps ²¹.
Myth If I kill the swarmers, the problem is gone.: Reality Vacuuming or spraying swarmers leaves the colony feeding on the house ⁴.
Myth I must sign today or the house will fall down.: Reality University of Maryland Extension says you can take weeks or even a few months to evaluate the problem and compare bids ³.

Where the species and season change by region

The termite in your soil depends on where you live. The invasive Formosan subterranean termite is found in Hawaii and the Southeast, north along the Atlantic coast to Virginia, inland to Tennessee and in southern California; in Florida it is mostly in dense urban areas ⁵.

Its swarms come later and at dusk. In Mississippi, eastern subterranean termites swarm February to April and Formosans May to June ⁴. In California, the desert species Heterotermes aureus flies July to September ².

Ask your inspector which species they found, because it changes the swarm calendar and how hard the colony is to control.

When it matters to you, and what to do next

Your next step depends on what you found. If you see swarmers only outside, note the date and watch. If you see swarmers indoors, mud tubes or hollow wood, book a licensed inspection. If you are buying a home, get a wood-destroying organism inspection before closing.

Collect a few swarmers or wings in a sealed bag. They help an inspector tell termites from ants and name the species.

Compare at least two plans. Ask which method, which areas, how long the protection lasts, what the warranty covers and how follow-up works. Our guide to choosing a pest control company lists the questions.

Decision guide What to do about what you found

If Swarmers outdoors only: Then Note the date and watch; yard swarms are common ²
If Swarmers indoors: Then The building is infested; book a licensed inspection ⁴
If Mud tubes on the foundation: Then Inspection before any treatment ²
If Already under a termite contract: Then Call that company first ⁴

Source: [2] [4]

Quick decision guide

A yard swarm alone means watch and note the date. An indoor swarm, mud tubes or hollow wood call for a licensed inspection. If you are under contract, call that company first, and if you are buying, get a WDO inspection before closing.

Questions about Subterranean Termite

What do subterranean termites look like?

Subterranean termite workers are about 1/4 inch long, soft, cream-colored and eyeless, according to University of Maryland Extension. Soldiers guard the colony with large jaws. Swarmers are dark brown to black with wings about equal in length. Most people see swarmers or mud tubes rather than workers, because workers stay inside soil, tubes and wood.

What are termite mud tubes?

Mud tubes are tunnels subterranean termites build from soil, saliva and bits of wood so they can travel from the soil to wood without drying out. They are usually about 1/4 inch wide.

UC IPM lists four kinds: working, exploratory or migratory, drop and swarm tubes. Breaking one open may show live termites. A tube on a foundation is a reason to book an inspection.

How do I know if mud tubes are active?

You cannot tell for sure from the outside, which is why a trained inspector checks. UC IPM notes that breaking a tube open may expose live workers and soldiers, which confirms activity.

An empty tube may be old, but other tubes, hidden galleries or a second colony can still be active. Leave the decision to a full inspection of the whole structure, not one tube.

When do subterranean termites swarm?

Most subterranean termites swarm in spring, but the timing depends on species and region. In Mississippi, eastern subterranean termites swarm from February to April and Formosan termites from May to June. UC IPM says western species swarm in spring or fall afternoons, often after rain, and the desert species flies July to September.

Can tent fumigation get rid of subterranean termites?

No, tent fumigation is not used for subterranean termites. UC IPM says fumigation, heat, freezing and electrocution are not effective against them in structures, because the colony lives in the soil. Control uses liquid soil treatments, bait systems or both. Fumigation is a drywood termite treatment.

How fast do subterranean termites damage a house?

Subterranean termite damage builds slowly, so University of Maryland Extension says you can take weeks or even a few months to evaluate the problem and get several bids. A colony large enough to swarm has usually been there several years, so damage may already exist where you cannot see it.

Do termite baits work on subterranean termites?

Yes, termite baits can control subterranean termite colonies, but they are slow. Workers eat a slow-acting active ingredient and share it. UF reports chitin-synthesis-inhibitor baits take about 3 months for worker die-off. UC IPM says baits may take months or years and need ongoing monitoring.

Should I treat subterranean termites myself?

Treating subterranean termites is a job for a licensed professional. Soil treatments often need trenching or drilling through concrete, and the EPA warns that a poor barrier treatment can contaminate a home or nearby wells and still not protect it.

UF notes over-the-counter products are unlikely to control Formosan termites. Owners can fix moisture and wood-to-soil contact.

How often should a house be inspected for termites?

A house with a history of subterranean termites should be inspected every few years at least. UC IPM suggests inspections every 3 to 5 years, and every several years for homes with past activity. Many termite contracts include a yearly inspection, which University of Maryland Extension recommends after an infestation.

What attracts subterranean termites to a house?

Moisture and wood near the soil attract subterranean termites. The EPA lists poor drainage, leaks, blocked vents, plants against the house and stored wood as risks.

UC IPM adds wood within 12 inches of soil and stucco that runs into the ground. Fixing these does not kill a colony but makes the house harder to reach.

Sources

U.S. EPA, Termites: How to Identify and Control Them, retrieved October 11, 2026.
UC Statewide IPM Program, Pest Notes: Termites (Publication 7415), retrieved October 11, 2026.
University of Maryland Extension, Termites, retrieved October 11, 2026.
Mississippi State University Extension, Bug’s Eye View: Eastern Subterranean Termite Swarmers (Vol. 8, No. 2), retrieved October 11, 2026.
UF/IFAS Extension, Formosan Subterranean Termite (IN278), retrieved October 11, 2026.

Expert review

Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.

How the numbers were checked: Biology, signs, species, swarm timing and treatment effectiveness follow UC IPM Pest Notes 7415, University of Maryland Extension, Mississippi State Extension and UF/IFAS IN278, attributed to each. Federal registration, label and safety points are from the EPA termite page.

Suggest a correction. We fix errors and say what changed.