Fire Ants in the House: Why They Come Inside and What to Do

Fire ants are an outdoor pest, so finding them on the kitchen counter, around the bathtub or streaming out of an outlet is unsettling. In Texas slab homes it happens more than most people think, especially after a long dry spell or a week of heavy rain.

The good news: fire ants inside almost always trace back to a colony outside or under the slab, and there’s a clear order of steps that fixes it. The bad news: the first thing most people grab, a can of ant spray, usually makes it harder. This guide explains why fire ants come inside, how to find where they’re getting in, and what to do first.

Fire ants come into Texas homes looking for water and food, mostly during hot, dry weather or when rain floods their colonies. They usually enter through cracks in the slab, plumbing openings, weep holes, or along wires and branches that touch the house, and colonies can sometimes nest in walls or behind appliances. Don’t spray the trail. Find where they’re coming in, treat the colony outside or at the entry point, use a bait labeled for fire ants indoors, and fix any leaks. Leave anything inside electrical equipment to an electrician or a licensed pest professional.

Why do fire ants come inside?

Texas A&M AgriLife’s urban fire ant guide says fire ants from colonies near a home sometimes forage indoors for food and moisture, especially in hot, dry summer months. It also notes that whole colonies sometimes move into buildings during floods or drought, nesting in wall voids, in the attic or behind large appliances.

In practice, there are three triggers:

• Drought and heat. When the soil dries out, colonies go deeper looking for moisture. AgriLife’s Wizzie Brown notes that dry weather can push fire ants into homes looking for water. Kitchens, bathrooms, laundry rooms and the area around the water heater are the first places they show up.
• Heavy rain and flooding. When the yard is saturated, colonies move up and toward higher, drier ground, and the edge of a slab is often the highest, driest spot around. Our guide to why fire ant mounds pop up after rain explains what’s happening under the lawn.
• Food. Fire ants eat almost anything: grease, pet food, sweets, dead insects. Once a forager finds food indoors, it lays a trail and others follow.

Is it fire ants or another ant?

Before you treat, make sure they’re fire ants. In Fort Bend County, tawny crazy ants are also confirmed, and they need a different approach.

AgriLife notes that fire ant workers vary in size from about 1/16 to 3/16 inch within the same colony, and that when a mound is disturbed, hundreds of workers run up vertical surfaces to sting. Texas A&M’s tawny crazy ant guide points out that crazy ants don’t build obvious mounds the way fire ants do. If you’re not sure what you have, our ant control page covers the other ants we treat in Rosenberg homes.

How do fire ants get into a slab home?

Fire ants don’t need much. In a typical Rosenberg brick-on-slab house, they come in through:

• Cracks and expansion joints in the slab, especially in the garage and where the garage meets the house.
• Plumbing openings in the slab. Bathtubs in slab homes usually sit over a “bath trap,” an opening left in the concrete for the drain. Ants can come up through it and appear around the tub, the toilet or the vanity.
• Gaps around pipes and wires under the kitchen and bathroom sinks, behind the washer and at the water heater.
• Weep holes in the brick. AgriLife suggests screening weep holes, not sealing them shut, because they let moisture drain out of the wall.
• The AC line and outdoor unit. Condensate lines drip water right where fire ants want it.
• Bridges. AgriLife points out that branches, shrubs and cables touching the house let ants climb over any treatment at ground level.

Where we find the entry point in Rosenberg homes

When we follow a fire ant trail inside a Rosenberg home, it most often leads to one of a few places: the expansion joint or a crack in the garage slab, the bath trap under a tub, the gap around the drain line under the kitchen sink, or the bottom of a wall where the brick weep holes meet a mound outside. Outside, we usually find the colony in the bed right against the foundation, beside the AC pad or along a sidewalk that holds heat. The trail you see in the kitchen is often 20 or 30 feet from where the ants are actually coming in.

What to do first when you find fire ants inside

1. Don’t spray the trail. It feels like the right move, but AgriLife says treating trails rarely solves an ant problem, and most store-bought sprays are repellent. They scatter the ants, hide the trail you need to follow, and keep ants from taking bait.
2. Protect people first. If ants are near a crib, a bed or someone who can’t move easily, move them away right away. AgriLife warns that fire ants indoors can threaten sleeping or bedridden people and pets. Check pet food and water bowls too.
3. Clean up the food. Wipe up spills and grease, seal food, and pick up pet food. Vacuum the ants you can see and empty the vacuum outside right away, as AgriLife recommends.
4. Follow the trail. Watch where the ants go for a few minutes. They’ll lead you to a crack, an outlet, a pipe or a baseboard. That’s your entry point.
5. Check outside. Walk the outside of the house at that spot. Look for mounds against the slab, in flower beds, by the AC unit and under the hose bib.
6. Fix the water. Repair a dripping faucet, a leaking pipe under the sink, a running toilet or an AC condensate line that drips by the slab. Water is often why they came in.

How do you get rid of fire ants in the house?

The fix has two parts: the colony outside and the ants inside.

Outside: treat the colony

AgriLife says it’s best to control fire ants in the yard before they move into the house. Treat the mounds near the house with a labeled mound treatment, then bait the yard using the Texas Two-Step method. If mounds keep showing up against the slab, the colony may be living under it.

Inside: bait, not spray

Use a bait that is labeled for fire ants indoors and follow the label. AgriLife warns that bait products not registered for fire ants may not work. Place bait along the trail and near where ants come in, not on it where you’ll wipe it away. Let the ants carry it back. Don’t spray near the bait.

Seal what you can

Once the ants are under control, caulk gaps around pipes and wires, seal cracks in the slab and along baseboards, and trim back plants and branches that touch the house. Don’t seal weep holes; screen them.

Fire ants in outlets, the AC unit or the breaker box

This one is not a do-it-yourself job. AgriLife says fire ants chew insulation, cause short circuits and pack soil into equipment, and Texas A&M estimates the damage to electrical equipment in Texas at about $11.2 million a year. For safety, AgriLife says only electricians or licensed pest control professionals should treat electrical equipment, and the power must be turned off first. Never spray liquid into an outlet or a breaker box.

What about fire ants under the slab or in the walls?

If you keep finding ants in the same room no matter what you do outside, the colony may be under the slab or inside a wall. AgriLife says whole colonies sometimes nest in wall voids, attics or behind large appliances. You may notice ants coming out of the bottom of a wall, around a light switch or behind the refrigerator or dishwasher.

These colonies need to be treated where they are, usually with a dust or a non-repellent product applied into the void or through the slab opening. That’s work for a licensed professional, who has the products and the tools to reach the colony without contaminating the home. Our fire ant control service treats the yard, the foundation and the entry points together, so the ants don’t just move to the next room.

When are fire ants indoors an emergency?

Call right away if fire ants are in a bed, a crib or a room where someone sleeps, if someone in the house is allergic to stings, or if ants are inside an outlet or the electrical panel. Our emergency pest control line is answered 24/7.

If someone is stung, a white pustule usually forms in a day or two. Don’t pop it. Texas A&M’s fire ant medical page says to get emergency help right away for chest pain, nausea, severe sweating, trouble breathing, serious swelling or slurred speech.

How to keep fire ants out

• Bait the yard twice a year. Spring and fall baiting keeps the colonies near the house down. The Rosenberg pest calendar shows when fire ants peak.
• Keep beds dry and clear. Pull mulch and soil back a few inches from the slab, and keep the edge of the foundation visible.
• Fix leaks fast. Outside spigots, irrigation lines and AC drain lines are fire ant magnets.
• Trim plants and branches that touch the walls or roof.
• Watch after storms. After heavy rain or a flood, walk the outside of the house and look for new mounds against the slab. Our guide to Rosenberg flood zones and pests covers what else moves in after high water.

FAQ’s

Why do I have fire ants in my house all of a sudden?

Usually because of the weather. Dry heat sends fire ants looking for water indoors, and heavy rain pushes colonies toward the higher, drier ground around your slab. A new food source, such as pet food or a spill, can also bring a trail inside quickly.

Can fire ants live in the walls of a house?

Yes. Texas A&M AgriLife says whole colonies sometimes nest in wall voids, attics or behind large appliances, especially during floods or drought. A colony in a wall needs to be treated where it is, not just where the ants come out.

Can fire ants come up through the foundation?

Yes. They come up through cracks, expansion joints and plumbing openings in the slab, including the opening under a bathtub. Colonies can also live under the slab, which is why mounds keep appearing against the foundation.

What kills fire ants inside the house?

A bait labeled for fire ants indoors, placed near the trail and the entry point, combined with treating the colony outside. Avoid store-bought sprays while you’re using bait; Texas A&M says they repel ants and keep them from taking it.

Are fire ants in the house dangerous?

They can be. Fire ants sting repeatedly, and Texas A&M warns they can threaten sleeping or bedridden people and pets. Anyone allergic to stings should get medical help right away for trouble breathing, serious swelling or chest pain.

Why are fire ants in my bathroom?

Bathrooms have water, and in slab homes there’s usually an opening in the concrete under the tub for the drain. Fire ants often come up through that opening and show up around the tub, the toilet or the vanity.

Fire ants inside your home?

We treat fire ants in homes across Rosenberg and nearby Sugar Land and Fulshear. Call (281) 549-0821 24/7 for a free inspection. We’ll find where the ants are getting in, treat the colony and give you a written price before any work starts. Or learn more about our pest control in Rosenberg.