Ant Control in Chester County: Identify the Ant, Then Treat the Nest

Why the species matters before anything is applied

One ant on the counter does not tell you the species or where it nests. Odorous house ants often nest outside under stones and boards and walk in along siding. Pavement ants live in the soil under slabs and sidewalks and come up through cracks. Carpenter ants hollow out damp wood in the structure. If all three get the same treatment, whichever species it does not fit keeps coming back.

So the first visit is about identification and tracing. We look at the size and color of the workers, follow the trail back toward where it enters, and check the places each species nests. Then we decide on bait type, placement and outside work.

Odorous house ants

The odorous house ant (Tapinoma sessile) is a native species and one of the ants people call "sugar ants." Workers are tiny, 1/16 to 1/8 inch, uniformly brown to black, and all about the same size. Crush one and you get a rotten smell, which is the easiest way to confirm the species.

Penn State Extension describes colonies of several thousand workers with many queens. Workers move fast in single-file lines and prefer sweets, though they also take dead insects and grease. Outside they feed on honeydew from aphids and on flower nectar, so shrubs with aphids next to the house can feed a colony right at your foundation.

Nests are usually outdoors under rocks, boards, mulch and garden timbers, but odorous house ants will also nest indoors in wall voids near warmth and moisture, and even in termite-damaged wood. Winged reproductives appear from May through July. Because there are many queens, killing the workers you see does little to the colony.

Pavement ants

The pavement ant (Tetramorium caespitum) is one of the most common house-infesting ants in Pennsylvania. Penn State says it was likely carried here in ship ballast soil from Europe in the 1700s and 1800s. Workers are about 2.5 to 4 mm long, dark brown to black, with fine parallel grooves on the head and thorax and two small spines on the back.

Colonies sit under sidewalks, driveways, building slabs and large rocks. The ants enter through cracks in foundation walls and basement or garage slabs, and the giveaway is small piles of sand or soil next to a slab crack or along the top of a foundation wall. They eat almost anything that hits the floor: sweets, grease, dead insects and seeds.

Swarms normally happen in spring. In heated buildings, Penn State notes pavement ant swarmers can show up in late fall and into February, which is why people sometimes see winged ants in a basement in winter and assume the worst.

Side by side: three common house ants

Why we bait instead of spraying the trail

Spraying a trail kills the workers you can see. The queens and brood are somewhere else, and the colony keeps sending foragers. Penn State Extension's guidance for both odorous house ants and pavement ants is baiting with slower-acting baits, because workers carry the bait back and share it with the queens and developing ants before it takes effect.

We place bait where ant activity is actually happening, in spots children and pets cannot reach, and match the bait to what the species is feeding on. Baits are topped up while the colony is still taking them. Penn State notes that control with bait can take two weeks or longer, so do not judge it by the first few days.

Outside, work focuses on nest sites and the entry points ants are using, following the product label. Before we start, we tell you what to leave alone (the bait placements, mainly) and how long to keep people and pets off any treated surfaces.

Our process on an ant call

Ant jobs follow The Davis Inspection Standard, laid out step by step on our inspection process page.

• Identify the species before anything is applied.
• Find and name the conditions: a leak under the sink, mulch piled on the siding, a slab crack, aphids on the foundation shrubs.
• Place bait and treatment where the colony lives and travels, per the label.
• Set the follow-up and tell you re-entry and prep up front.

What brings ants inside here

Southeast Pennsylvania housing gives ants plenty of routes. In Norristown borough, 47.1% of homes are single-unit attached houses, according to Census ACS 2020 to 2024 estimates, and shared walls let a colony forage through more than one kitchen. Our page for Norristown homeowners has more on that housing. Newer townhomes and colonials usually sit on slabs or poured basements with garage slabs, the exact surfaces pavement ants nest beneath.

These homeowner fixes cut down on ant traffic:

• Fix plumbing leaks and damp spots under sinks and dishwashers.
• Keep mulch and stone a few inches back from siding and the foundation.
• Caulk cracks in slabs and foundation walls where you see sand piles.
• Wipe up sweet spills and keep pet food in sealed containers.
• Deal with aphids on shrubs planted against the house.

Carpenter ants need a different approach

Large black ants, a quarter to half an inch long, walking around the house at night are probably carpenter ants. They nest in moist or rotting wood, push out piles of coarse shavings, and send winged swarmers out in spring. The treatment depends on finding both the outdoor parent colony and any satellite nest in the house. Our carpenter ant control page covers the signs, the moisture problems behind them and how we treat them.

Flying ants vs termite swarmers

Winged ants and termite swarmers both show up in spring. Ants have a pinched waist, elbowed antennae and front wings longer than the back ones. Termites have a thick waist, straight antennae and four wings of equal length. If you find a pile of shed wings on a windowsill, save a few in a bag and call, and see our page on eastern subterranean termites.

If ants are a yearly problem along with stink bugs and spiders, a seasonal home pest control plan may make more sense than single calls. C.R. Davis III & Sons is family owned, licensed with the Pennsylvania Department of Agriculture and insured. Call (610) 935-9130.