Native subterranean termites swarm in early spring, usually in the afternoon. Formosan subterranean termites, established along the Charleston coast since the 1950s, swarm from about mid-May into July, most often in the evening and drawn to lights. A swarm seen indoors means winged reproductive termites have come from a colony nearby, which calls for an inspection.
Key takeaways
- Native subterranean termites usually swarm in early spring, and they tend to do it in the afternoon.
- Formosan subterranean termites swarm from mid-May to July, and their flights are mostly in the evening.
- Formosan swarmers are drawn to lights, so the first sighting is often at a porch or window light after dark.
- Sources differ on when Formosan swarming starts, so planning around mid-May is safer than waiting for a late-May date.
- A swarm indoors means reproductive termites have reached the building, which points to a colony close by rather than proving how much wood is affected.
- Time of day and season help separate native from Formosan termites, but a swarm alone does not identify the species or the extent of damage.
Which termites swarm in spring, and when?
Native subterranean termites are the ones that swarm in early spring, and in this area they usually do it in the afternoon. That timing is one of the more useful details a homeowner can know, because it separates them from the Formosan termites that swarm later in the year.
Native subterranean termites live in soil and feed on wood that touches the ground or sits close to moisture. When conditions are right, a colony releases winged reproductive termites, called swarmers, that leave the nest in a short and often visible flight. The Clemson Home and Garden Information Center, known as HGIC, describes the native species as swarming in early spring, usually in the afternoon.
The swarm is not the damage itself. It is the stage at which a colony sends out new reproductive termites to start new nests, which means the colony already exists somewhere nearby. A reader who sees swarmers in the afternoon early in the spring should take it as a reason to have the structure looked at, not as proof of a particular problem. A technician will look at the wood, the soil contact and the sub-floor before saying what is present.
When do Formosan termites swarm in the Lowcountry?
Formosan subterranean termites swarm from mid-May to July, and most of those flights happen in the evening. HGIC gives that window, while a newspaper account put the start in late May to early June, so the honest answer is that sources differ on the first few weeks.
The Formosan species is what sets the Charleston area apart from much of the rest of the country. Clemson HGIC says the species was introduced into South Carolina in the 1950s and dates its arrival in Charleston to the mid-1950s. Since then it has spread through many areas of Charleston County, with infestations concentrated in the coastal areas from Charleston south to Beaufort. Its swarms are a warm-season event, which is why the mid-May to July window is the one most useful for planning a visit or a check.
Because the start of the window is reported differently, a reader should not treat a single date as a rule. A press account put Formosan emergence in a narrower late-May to early-June window, which disagrees with the HGIC start. The safer reading is to expect swarmers from about the middle of May and to keep watching through July. Whatever the calendar date, the time of day is more consistent: Formosan swarms come in the evening, while native swarms appear in the afternoon. A homeowner with questions about Formosan subterranean termite treatment should bring that timing to the inspection.
Why do Formosan swarmers come out at dusk and gather at lights?
Formosan swarmers are drawn to lights, and HGIC describes their flights as mostly in the evening. That makes a porch light or a lit window the place where many people first notice them, often without knowing what they are looking at.
A termite swarm is a reproductive flight. The winged termites leave the colony to pair up and begin new colonies, and they need the right conditions to fly and find mates. The Clemson guidance that Formosan swarmers are drawn to lights is one of the more useful behavioral details for a homeowner, because it explains why the swarm often appears at a door, a window or a garage light after dark rather than out in the open yard.
A light is also a clue about where to look, but it is not a location. Swarmers can travel from the trees, the lawn or the wall, so a swarm collected under a light near the house does not tell you where the colony sits. A technician reads the swarm together with the structure, the ground around the foundation and any wood in contact with soil, rather than assuming the light is the source. A reader who finds swarmers at a porch light in the evening should write down the date, the time and the exact spot, because those details help a technician decide what to check first.
Why did Formosan termites become established in Charleston?
Formosan termites were introduced into South Carolina in the 1950s and reached Charleston by the mid-1950s, according to Clemson HGIC. Their spread since then has depended largely on people moving infested material from one place to another.
The species is not native to the Lowcountry. Clemson HGIC places its introduction in South Carolina in the 1950s and dates its arrival in Charleston to the mid-1950s. Clemson entomologists' research and citizen reports put it in sixteen South Carolina counties, and the university notes that it is in many areas of Charleston County. A colony that has been present in the same ground for decades gives the species a large footprint, so a home in the county may sit close to an established population rather than at the edge of a rare one.
Clemson's guidance also says that people are the main cause of the species spreading to new places, by moving infested material. Old railway ties are one example it names. For a homeowner, the practical point is that a termite problem can arrive on material someone brought in, such as lumber, old timbers or a load of landscaping stock, and not only by a colony slowly working outward.
What does a termite swarm indoors actually mean?
Finding swarmers inside a house means winged reproductive termites have reached the living space, usually from a colony nearby. It is a reason to have a technician look at the structure, not a diagnosis of how far the damage goes.
Swarmers are the reproductive members of a termite colony. After they fly, they land, shed their wings and try to start a new colony, which is why a swarm is so easily mistaken for flying ants. Indoors, a common reaction is to sweep up the wings and assume the matter is finished. The wings are only the evidence that a swarm happened. They do not show whether the colony is in the wall, under the floor, in a tree or in a neighbour's yard, and they do not show whether it has been working on the wood for months.
A reader who finds swarmers indoors should note where they were, what time of day it was, and whether they were on a window, a light or the floor. Then call a technician. The technician will check the structure for wood, soil contact and the moisture that subterranean termites depend on. The swarm is a clue, and the inspection is what turns that clue into a finding that can be acted on.
Can a swarm tell you which termite it is?
Not reliably. Timing and time of day help separate native subterranean termites from Formosan, but a swarm does not reveal whether a drywood species is involved, and it does not show how much damage has been done.
The timing rules in this guide are useful, but they are not a full identification. Subterranean termites need contact with soil or a steady moisture source. Drywood termites do not. They nest inside the timber itself, with no soil contact, which is why a soil barrier does not address them. The research available for this area did not produce a reliable month-by-month swarm calendar for the drywood species, so this guide does not offer one. Naming the mechanism is more useful than naming a month that could be wrong,
For that reason, a technician treats a swarm as a starting point for an inspection rather than an answer. The species matters because the approach differs, and so does the place to look. Subterranean termites are usually found where wood is in contact with soil or moisture. Drywood termites are found inside the timber, sometimes well away from any soil line. A homeowner cannot make that call from the outside of the house, and a guess can send the work in the wrong direction.
What does a termite bond have to do with a swarm?
A termite bond can change what is covered, so the first step after a swarm is to read the current contract. Clemson HGIC advises asking the holding company which subterranean termites and which damage the bond covers.
A homeowner who already has a termite bond often finds that a swarm is the moment the paperwork gets opened for the first time. HGIC advises a homeowner under a bond to read the current contract and to ask the holding company which subterranean termites and which damage are covered. Depending on the terms, the contract may need to be amended or rewritten. Those are details about the agreement rather than about the insect, and they are worth checking before deciding what the swarm means for the house.
A bond is also a reason to tell the holding company about a swarm before assuming it is covered. The contract states which species and which kinds of damage are included, and that wording is what decides the next step. Anyone without a bond should ask what an inspection will cover before any work begins. The price is explained and approved before work starts, and the scope of the job is what moves the quote, so a clear description of what was seen makes that conversation easier.
What should you do if you see swarmers?
Write down the date, the time, the place and what the swarmers looked like, then have a technician inspect the structure. Keep a few of the wings or insects if you can, since they help identify what you saw.
Start with the basics. Note whether the swarm happened in the afternoon or the evening, where it was, and whether shed wings were on a sill, a floor or a window. A short note like that is more useful to a technician than a general description. If the swarm happened at a light, say so, because Formosan swarmers are drawn to lights and that detail points toward the species. If you can, put a few of the insects or wings in a sealed container so they can be looked at later.
Then call a technician at (855) 974-4733. The phone line is answered 24/7. A visit the same day is possible when a technician is free, but no arrival time or result can be promised in advance. The technician will look at the wood, the soil contact, the moisture and any sub-floor access before recommending anything. The aim is to answer the question the swarm raised, not to sell a treatment before the cause is known.
Frequently asked questions
Is a swarm in May the same thing as one in March?
Not necessarily. Native subterranean termites swarm in early spring, usually in the afternoon, while Formosan subterranean termites swarm from about mid-May into July, mostly in the evening. A spring afternoon swarm points toward the native species and an evening swarm in early summer points toward Formosan, although a technician should still confirm which it is. Two swarms in two seasons can easily come from two different colonies.
Why do termites seem to appear only at night?
The Formosan swarms are the ones that come out in the evening, and HGIC describes them as drawn to lights. The native swarms are described as afternoon events, so the time of day is part of identification rather than a curiosity. Light is what makes a swarm visible near a house, which is why a porch light is often where people see them first. A reader who records the time has a more useful note for the technician.
How can I tell a termite swarmer from a flying ant?
Often you cannot tell from a glance, and a homeowner should not rely on one. Swarmers shed their wings after landing, so the wings on a windowsill may be the only sign that a swarm happened. Because the colony matters more than the single insect, the most practical step is to describe the swarm and let a technician look at it. Keep a few samples if you can.
Does a swarm mean the house is already damaged?
Not necessarily. A swarm shows that a colony is nearby and that reproductive termites have left it, but it does not show how much wood is affected. The extent of any damage is found by inspection, not by the swarm itself. That is why the next step is a look at the structure, including the sub-floor and any wood that is in contact with soil or moisture.
What should I read on a termite bond after a swarm?
Read the current contract and ask the holding company which subterranean termites and which damage it covers. Depending on the terms, the contract may need to be amended or rewritten. A swarm is a good reason to read the document before deciding what happens next. Keep the paperwork with the house records so the next inspection can be compared against it.
Sources
This guide is general information for Charleston homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.