Subterranean termite (swarmer)

How to recognise it

These are the features that identify a subterranean termite (swarmer). Each one is described in words so the identification works without the diagram.

1. The waist is broad and straight — the body reads as a single uniform tube with no pinch. A flying ant has a sharply pinched, narrow waist. This is the most reliable feature.
2. All four wings are the same length and shape, and extend well past the tip of the abdomen. A flying ant's forewings are clearly longer than its hindwings.
3. The antennae are straight and beaded like a tiny string of pearls, not elbowed. A flying ant's antennae bend sharply.
4. Wings detach very easily, so piles of equal-length discarded wings on windowsills and in spider webs are often the first evidence found.
5. Body is dark brown to black, 6 to 10 mm including wings.

What it leaves behind

• Pencil-width mud tubes on foundation walls, piers, and crawl space surfaces — the definitive subterranean termite sign.
• Piles of shed wings of equal length on windowsills, in spider webs, or near light fixtures, typically in spring.
• Wood that sounds hollow when tapped, and blistered or darkened paint over damaged areas.
• Damaged wood packed with soil, which distinguishes subterranean damage from the clean galleries of drywood termites.

Why an infestation persists

This is the mechanism that explains why treating visible damage does not solve the problem. Subterranean colonies live in the soil, not in the wood they eat, and reach the structure through shelter tubes that protect them from drying out. The colony may be substantial and some distance from the damage you can see, so removing or repairing damaged wood addresses the symptom and leaves the colony intact. Swarming is a reproductive event from a mature colony — typically several years old — which is why swarmers indoors are a serious finding rather than a nuisance. Foraging is driven by moisture, so anything that keeps soil damp against the structure increases pressure.

Where it occurs

Every state except Alaska, with the greatest activity across the Southeast and the southern half of the country. Formosan subterranean termites are established along the Gulf Coast, in Hawaii, and in parts of California.

Where to look for it

• The full perimeter of the foundation wall, inside and out, looking for pencil-width mud tubes running vertically from soil to timber.
• Crawl space piers, the underside of floor joists, and the sill plate, which is where tubes are found most often and where a torch and a mirror earn their keep.
• Behind and beneath anything stored against a foundation wall, since tubes are routinely built in the covered gap behind stacked boxes or timber.
• Expansion joints, plumbing penetrations, and the gap where a slab meets a wall, which give access with no visible tube at all.
• Windowsills and spider webs in spring, for piles of shed wings of equal length.
• Any timber that sounds hollow when tapped, or where paint is blistered or dimpled over a soft area.

When you see it, and why

Swarming is the event most people notice, and in most of the country it happens on warm days in spring, frequently after rain and often around midday. That timing matters for a practical reason: a swarm indoors is a once-a-year signal from a colony that has been feeding for years, so the absence of swarmers for eleven months of the year says nothing about whether a colony is present. Foraging itself continues year-round in the southern states and through most of the year elsewhere, because the soil below frost depth stays workable. Inspecting only in spring, when the visible signal appears, is how infestations run for a decade undetected.

What getting the identification wrong costs you

Mistaking a subterranean infestation for drywood termites sends the entire response to the wrong place: drywood work targets infested timber, while a subterranean colony lives in the soil and is untouched by it. The reverse error is equally expensive, committing a homeowner to soil treatment around a structure whose problem is inside a single piece of furniture. Mud tubes settle it. Mistaking swarmers for flying ants is the cheaper error only because it delays rather than misdirects — but a delayed termite finding is measured in structural damage.

What a professional actually does

A full inspection covers the accessible perimeter, the crawl space or slab edge, and any timber in contact with soil, and produces a diagram showing where evidence was found and where conditions are conducive. The report should separate those two findings clearly, because conducive conditions are a correction list rather than evidence of termites. Treatment approaches target the soil or the colony rather than the damaged timber, and any warranty should state in writing whether it covers retreatment only or retreatment plus repair of new damage. Ask what is excluded and what voids it before signing.

What it costs

Subterranean termite work is priced on linear footage of foundation rather than floor area, which is why two houses of the same size can be quoted very differently. A slab, a crawl space, and a finished basement are three different jobs. The figure that matters over time is not the initial treatment but the renewal: bonds are annual, frequently require a paid inspection to stay valid, and the difference between retreat-only and retreat-and-repair coverage can exceed the original treatment cost over a decade. Get the first-year total and the renewal terms in the same document.