Termite Swarm Season in Maryland: Timing, Swarmers and Flying Ants

When is termite swarm season in Maryland?

Eastern subterranean termite swarms in Maryland are typically a spring event, with a peak often falling in May and June and early swarmers possible on warm, damp days in March and April. Timing shifts with temperature and rain. Swarmers usually emerge on a warm day after rain, and a swarm lasts only a short while.

A swarm is a mature colony's way of spreading. Winged reproductive termites, called alates, leave the colony together, fly a short distance, shed their wings and try to pair up and start new colonies in damp soil. Most do not survive, but a swarm is a sign that a large, established colony is somewhere close.

In the Baltimore area, the weather changes quickly in spring, so the swarm window is not a single date. A warm, humid afternoon after a day or two of rain is the classic trigger. The same insects may emerge from several points at once, from a tree stump in the yard, a damp piece of wood on a porch or a crack in the foundation.

The calendar below is a guide to what is typical. Treat it as a reason to look, not as a deadline. If you see winged insects at any time of the year that you cannot identify, a photograph helps. Our Baltimore pest calendar shows how the termite window fits with ants, mosquitoes and the rest of the year.

How do I tell termite swarmers from flying ants?

Check three features: antennae, waist and wings. Termite swarmers have straight, bead-like antennae, a broad waist and four wings of equal length. Flying ants have bent (elbowed) antennae, a narrow pinched waist and front wings longer than the back pair. The differences are small, so look closely or photograph the insect.

The two insects are about the same size and both appear in spring, which is why they are so often confused. The difference matters, because swarming termites point to a colony that eats wood, while swarming ants may only be a nuisance, unless they are carpenter ants nesting in damp wood.

A clear photograph on a white sheet of paper, or the insect stuck to a piece of clear tape, is usually enough for a technician to tell the difference. Discarded wings are another clue. Termite swarmers shed their wings soon after landing, and the wings are all about the same size, so small piles of near-identical wings on a windowsill or in a spiderweb are a typical sign.

What does a swarm mean for my Baltimore house?

A swarm outdoors tells you a colony is nearby, but not that it is in your house. Swarmers indoors, shed wings on sills, mud tubes on foundation walls or soft, hollow wood are stronger signs that termites have reached the structure. In either case, an inspection is the way to find out, not guesswork.

Eastern subterranean termites live in the soil and travel to wood through mud tubes, which they build to hold in moisture. They can also enter through hairline cracks in foundations and gaps around pipes. They work slowly, and much of the damage is hidden inside joists, sills and framing before anything shows.

Baltimore's older housing stock gives them places to work. Many rowhouses have brick or stone foundations, wood joists and floor framing that touches the cellar, and porches and steps built close to the ground. A damp cellar or a leaking downspout can make a piece of wood easier to eat. It is also true that every house is different: a termite problem is about moisture, wood and soil contact, not the age of the house on its own.

In an attached rowhouse, you may be next to a house with its own history. Termites do not respect a party wall, though how far they travel is hard to say without looking. Tell a technician which side shares the wall and whether neighbours have had treatment, because it changes where to look.

For the full picture of what treatment involves, see termite control. For finding out whether there is anything to treat, termite inspection is the starting point.

Could it be carpenter ants instead of termites?

Yes. Carpenter ants swarm in spring too, and they nest in wood that has been damp. They do not eat wood the way termites do; they excavate it and push out coarse sawdust-like frass. Carpenter ants are larger, and their workers are often seen at night. A technician can confirm which one you have.

Carpenter ants are among the likeliest lookalikes in a Baltimore house, because they love the same moisture-damaged wood that termites do: a leaky window frame, a porch post, an old roof leak. On detached houses with mature trees, such as those around Roland Park and Govans, they often nest in a tree or stump and forage across the yard toward the building.

The signs differ. Termites leave mud tubes and eat along the grain, leaving a layered, maze-like pattern. Carpenter ants leave clean, smooth galleries and little piles of frass, which looks like fine wood shavings often mixed with insect parts. Workers are large for ants, and they may be seen walking along baseboards at night.

Because the treatment differs, getting the identification right matters. See carpenter ant control for how they are handled, and ant control if the insects turn out to be a more ordinary trailing ant.

What should I do if I find swarmers indoors?

Stay calm, keep a few specimens, photograph the area and arrange an inspection. Swarmers die within hours without moisture, so there is no need to panic. Vacuum up the rest, but do not spray the area heavily, because that can hide evidence a technician needs. Note where they appeared and any damp or damaged wood nearby.

Swarmers are drawn to light, so they often gather around windows and doors. They cannot bite or sting, and they do not eat wood themselves. The insects inside the house are the dispersing reproductives, not the workers doing the damage, and their wings fall off in short order.

The most useful thing you can do is collect evidence. Take photographs and save a few insects, plus any wings, in a small jar or taped to paper. Note the date, the time, the weather and the room. If they came from a specific crack, a baseboard or a window frame, mark it with tape.

Then look around. Check the cellar for mud tubes on the walls or around pipes, probe suspect wood gently with a screwdriver, and look for blistering paint or sagging floors. Do not tear anything open. A technician will look at the same places with a moisture meter and a probe. Calling (855) 974-4733 gets you a conversation about what you saw and whether a visit makes sense, and the price is confirmed before any work starts.

• Photograph the insects and any shed wings before cleaning up.
• Save a few specimens in a jar or on clear tape.
• Check the cellar, porch and sills for mud tubes, soft wood or frass.
• Fix leaking gutters, downspouts and pipes that keep wood damp.
• Do not move infested wood around the property.

Do I need a termite inspection when buying or selling in Baltimore?

Not always, but often. A wood-destroying insect (WDI) inspection is a common part of buying a house, and lenders and contracts sometimes ask for one. If you are buying an older rowhouse or a detached house with a wooden porch, an inspection before settlement is a sensible way to find hidden problems early.

An inspection looks at the structure for evidence of termites, carpenter ants and other wood-destroying insects, and for conditions that invite them: moisture, wood in contact with soil, clogged gutters and cracked foundations. Many of the best clues are in the cellar and around the porch, which is where an inspector will spend much of the time.

If you are selling, an inspection ahead of listing can remove a surprise from the contract. If you are buying, ask what areas the inspector could not reach, because finished cellars and enclosed porches can hide a lot.

Maryland regulates the business side of this work. The Maryland Department of Agriculture licenses pesticide businesses, and structural pest control firms must hold a pesticide business license with at least one certified applicator. People who inspect for pests or make recommendations need consultant certification. Ask any company about its license. For more detail on what goes into a visit, see termite inspection.

How can I make my house less attractive to termites?

Reduce moisture and remove wood that touches soil. Fix leaking gutters and downspouts, keep soil and mulch off foundation walls and siding, repair roof and plumbing leaks quickly, and keep firewood and lumber off the ground and away from the house. These steps do not make a house termite-proof, but they remove what termites need most.

Termites need moisture, and in Baltimore, with annual precipitation averaging about 43.6 inches at BWI, there is plenty of it. The best habits are dull but effective: gutters that drain away from the building, downspout extensions, grading that slopes away from the foundation, and a dry cellar with working ventilation or a dehumidifier.

Keep wood from touching soil. Porch steps, deck posts, trellises and fence boards that sit directly in the ground make an easy bridge. Pull mulch back from the foundation, trim shrubs off the walls and store firewood off the ground and away from the house.

Walk the house each spring, before the swarm window. Look for cracked paint on window sills, soft spots in porch boards, and mud tubes on foundation walls. If anything looks off, call early, because termite damage grows quietly. A routine general pest control plan does not replace a termite inspection, but a technician on a regular visit may notice warning signs.