It happens on a warm, still evening, usually after rain. The porch light is suddenly covered in winged insects, a few dozen find their way inside, and by morning there are wings on the windowsills. In parts of Florida, that scene can be a Formosan subterranean termite swarm, and the first evening is when most people make their decisions about it.
Swarm season is months away as this is written. That makes now the useful time to learn what a swarm means, what to do that night, and which preparations make the next season less stressful.
What a Formosan swarm is
The Florida Department of Agriculture and Consumer Services (FDACS) runs a Formosan Termite Program and publishes a consumer FAQ that answers most of what homeowners ask. Like all termite species, Formosans send out winged reproductives, called alates, to find new territory and start new colonies. According to FDACS, Formosan alates are golden brown with small hairs all over their wings and fly in massive swarms from April to July (FDACS, Formosan Termite Consumer FAQ).
The timing is specific. FDACS says swarms typically emerge between 8 and 10 p.m. on evenings with low winds and high humidity, especially after rain, and that the swarmers are attracted to white light.
Formosans are subterranean termites. According to FDACS, they live primarily underground and favor dark, moist, hidden environments, which they can also find in walls, attics and trees. FDACS notes that their colonies can extend as deep as the water table.
What to do that evening
Turn off the lights
Because swarmers are drawn to white light, FDACS recommends turning outside lights off, or switching to yellow bug lights, if you see a swarm. Indoors, the same logic applies to lamps near windows and doors. Formosans come in through windows, doors, exhaust fans and attic openings.
Vacuum the ones inside
FDACS’s instruction is direct: swarmers in the house should be vacuumed up and disposed of as soon as possible. The department adds that ninety-nine percent of swarmers die within a few hours if they find no moisture.
Notice where they are coming from
This is the observation that matters most for what happens next. FDACS draws a clear line between two situations:
- In a neighborhood that is highly infested, you should expect to see a few to 100 swarmers in the house during swarm season. FDACS says the presence of a few swarmers does not necessarily mean your home is infested.
- If the home itself is infested and the colony is in the walls or attic, FDACS says you would see several hundred to thousands of swarmers in the house, and the termites can chew through and break out of walls and ceilings.
So before you vacuum everything, take a moment to note whether the insects are gathered at windows and doors, which suggests they flew in, or whether they seem to be emerging from a wall, a ceiling, a baseboard or a crack in the slab. A few clear photos and a note of the time and rooms will help whoever inspects the house later.
Do not reach for a spray can
FDACS strongly recommends that homeowners do not treat for termites themselves, because they do not have access to current bait systems, chemicals and the equipment needed to treat under a home’s foundation. The department advises using a licensed pest control company instead, and you can confirm a company’s license through the FDACS pest control section.
Why Formosans get attention other termites do not
Three details from the FDACS materials explain why a Formosan swarm is taken seriously.
- They get through small gaps. FDACS says Formosans cannot chew through concrete but can displace small grains of it, and they exploit cracks the thickness of a credit card to get through slabs. They have been known to chew through, but not eat, soft metals, PVC pipe and rubber.
- They can live above ground. FDACS describes aerial colonies, which have no connection to the ground. These form when swarmers find a cellulose food source, a moisture source such as a pipe or roof leak, and a hidden space.
- They nest in trees. According to FDACS, Formosans can infest live, healthy trees, and trees close to a house can act as a reservoir that needs to be checked by a licensed pest control company or a certified arborist.
The aerial colony point is the one homeowners tend to overlook. A slow roof leak or a dripping line in an attic is not only a water problem in a Formosan area. It can be the moisture source a colony needs.
Preparing before the next season
FDACS publishes a prevention list on its Formosan Termite Prevention and Protection page. The practical items are:
- Have the home inspected annually by a licensed pest control company.
- Keep gutters clean, and extend gutter and drainage systems at least 1 foot away from the home.
- Take care not to disturb the termite treatment around the foundation.
- Repair cracks in the foundation and around the exterior, and repair any leaks in or around the home immediately.
- Eliminate wood-to-soil and stucco-to-soil contact, and keep plant material away from the exterior and foundation.
- Direct sprinklers away from the house.
- Turn off porch lights or use a yellow bug light during swarm season.
Several of these overlap with what inspectors call conducive conditions, which we cover in more detail in our article on conducive conditions around a Florida foundation. Our termite control page describes what an inspection typically looks at.
Questions homeowners ask
When do Formosan termites swarm in Florida?
FDACS says Formosan swarms occur from April to July, typically between 8 and 10 p.m. on evenings with low winds and high humidity, especially after rain.
Do a few swarmers in the house mean my home is infested?
Not necessarily. FDACS says that in a highly infested neighborhood a few to 100 swarmers indoors is to be expected during the season, while an infested home would see several hundred to thousands. Where they appear to come from matters as much as how many there are.
Should I spray the swarm?
FDACS strongly recommends against treating for termites yourself. Vacuuming the swarmers that come inside and turning off lights are the steps the department describes for the evening itself.
Can Formosan termites get through a concrete slab?
They cannot chew through concrete, according to FDACS, but they can work small grains loose and use cracks as thin as a credit card to get through slabs and structures.
If swarmers appeared inside rather than at the windows, the broader warning signs on our page about when a pest problem needs a professional are a reasonable next read. Homeowners on the southwest Gulf coast can also start from our Sarasota area page.
Checking what is available in your area
floridapestcontrolpro.com is a connection service. We do not perform pest control and we do not employ technicians. If you would like to be matched with participating providers based on your service area, you can use the request options on this site. Availability varies by area and by season, and you decide whether to move forward with anyone you speak to.