Florida's subterranean termite pressure is the highest in the continental United States. The Eastern Subterranean termite (Reticulitermes flavipes) is found statewide, and the far more destructive Formosan Subterranean termite (Coptotermes formosanus) has established dominant populations in coastal and urban areas from Miami to Tampa. Unlike drywood termites — which live entirely within the wood they consume — subterranean termites nest in soil and travel upward through mud tubes to feed on your structure.
That soil connection is why subterranean termites are so hard to detect. Most of their activity happens in walls, under floors, and inside structural framing where you can't see it. A mature subterranean colony can contain hundreds of thousands to several million workers. By the time visible damage appears, the colony may have been feeding for two to four years.
Here are the five signs that indicate subterranean termite activity — any one of them warrants an immediate professional inspection.
Mud Tubes on Foundation Walls, Piers, or Slab Edges
Subterranean termites need to maintain contact with soil and cannot survive exposure to open air. To travel from their underground colony to the wood in your structure, they construct shelter tubes — narrow, pencil-thick tunnels made from soil, saliva, and fecal material. These mud tubes are the single most reliable indicator of subterranean termite activity.
Look for them along foundation walls (interior and exterior), along concrete block piers in crawl spaces, at slab joints and expansion gaps, along water pipes and conduit that enter through the slab, and on garage walls near the floor. Active tubes appear moist and dark. Inactive tubes dry out and crumble easily. If you break open an active tube, you'll see worker termites — small, cream-colored insects — retreating rapidly. A tube with no insects doesn't mean the colony is gone; termites often abandon tubes temporarily and may be feeding elsewhere.
Discarded Swarmer Wings Near Windows or Lights
Termite swarms are how colonies reproduce and expand. Reproductives — called alates or swarmers — emerge in large numbers, take flight, mate, shed their wings, and attempt to start new colonies. In Florida, Eastern Subterranean termite swarms occur primarily from February through May, often triggered by warm, humid weather after a rain. Formosan termite swarms typically occur in May and June, usually in the evening and are attracted to lights.
After a swarm, you'll often find piles of discarded wings on windowsills, near sliding glass door tracks, around exterior light fixtures, and on countertops near windows. The wings all detach at the same point and are of equal length — unlike ant swarmers, which have two differently sized wing pairs. If you see a pile of small, uniformly shaped wings with no body attached, termites have swarmed from within or near your structure. Even if you see the actual swarm event — a dense cloud of winged insects — resist the urge to spray. Swarmers don't feed on wood, and killing them doesn't affect the colony.
Hollow-Sounding Wood When Tapped
Subterranean termites consume wood from the inside out, following the soft springwood between growth rings. The outer surface often appears completely normal while the interior is riddled with galleries. A hardwood baseboard or door frame may look pristine but contain nothing but termite-consumed honeycomb inside.
Walk along baseboards tapping with a screwdriver handle or your knuckles. Solid wood produces a sharp, dense knock. Wood that has been hollowed by termites produces a distinctly different sound — dull, papery, almost hollow. Pay particular attention to areas near soil: baseboards along slab edges, door frames near the threshold, window frames at the sill level, and any wood that penetrates through or near the floor. Wood near a bathroom or kitchen — where plumbing runs — is also high-risk territory, since any moisture from a slow leak makes that wood even more attractive.
Sagging Floors, Bubbling Laminate, or Bowing Baseboards
When subterranean termites consume enough of a structural member, the wood loses its load-bearing capacity and begins to compress or fail. You may notice laminate or hardwood flooring that suddenly feels spongy underfoot, small blistering or bubbling in laminate near seams, crown molding or baseboards that bow away from the wall slightly, or floors that creak in new places that were previously solid.
These signs typically indicate a more advanced infestation where structural members — subfloor, joists, or wall studs — have sustained significant damage. However, some homeowners notice flooring issues relatively early when termites consume the subfloor directly beneath a high-traffic area. Flooring bubbling that resembles moisture damage, but without any obvious water source, is a particularly important flag worth investigating.
Doors and Windows That Suddenly Stick or Bind
When termites damage door frames and window frames, the structural integrity of the frame changes. As termite-damaged wood absorbs moisture and begins to compress under load, frames can shift or warp subtly. The result is a door or window that used to open and close smoothly but now requires extra force, sticks at certain points, or leaves uneven gaps.
This sign is easy to dismiss — doors and windows do swell seasonally in Florida's humidity. But if a door you've owned for years suddenly starts binding without a corresponding weather change, it's worth investigating the frame. Check the door frame corners and the area where the frame meets the floor or sill. If the wood sounds hollow or feels soft when pressed, schedule an inspection.
Understanding Subterranean vs. Drywood Termites
Not all Florida termites are subterranean. The state is also home to significant populations of drywood termites — primarily the West Indian Drywood termite (Cryptotermes brevis) — which live entirely within dry wood without soil contact. Drywood termites leave behind different evidence: small, six-sided fecal pellets (frass) that accumulate in piles below kick-out holes, but no mud tubes. The five signs above apply specifically to subterranean species.
The Formosan Subterranean termite deserves particular mention. Coptotermes formosanus is an invasive species first established in Florida in the 1980s and now prevalent in coastal and urban communities. Formosan colonies can exceed one million workers — far larger than native subterranean colonies — and can cause structural damage at a significantly accelerated rate. A Formosan infestation is a genuine emergency requiring immediate professional intervention.
Swarm season alert: Eastern Subterranean termites swarm February through May in Florida. Formosan termites swarm May through June, typically after dusk near lights. If you witness a swarm event, document it with photos and call a licensed inspector the same day.
What Not to Do If You Suspect Termites
Two common mistakes can make a termite problem significantly worse:
- Don't disturb the colony. Breaking open mud tubes, poking into damaged wood, or removing materials that termites are actively using can cause them to scatter and retreat deeper into the structure, spreading the infestation and making treatment more difficult.
- Don't apply DIY spray products. Retail contact insecticides labeled for termites may kill the termites they directly contact, but repellent chemicals alert the colony and cause foragers to route around the treatment zone. This delays professional treatment and can spread the colony laterally through the structure.
The correct response is to photograph what you've found, avoid disturbing it, and contact a licensed pest control professional. A trained inspector can trace mud tubes back to their source, probe suspected areas systematically, and recommend whether liquid termiticide barrier treatment, a baiting system, or a combination approach is appropriate for your situation.
For homes being bought or sold, a WDO inspection documents all evidence of wood-destroying organisms and provides the official Florida Form 13645 required by most lenders. If you suspect an active infestation, professional termite control should be addressed before or in tandem with any real estate transaction. For homeowners who want to understand their broader Florida termite risk, see our guide on how common termites are statewide.