The ants you see are a fraction of the problem
The ants on your counter are foragers from a colony that can number in the thousands, usually nesting outside or in wall voids. Killing foragers doesn't reduce the colony — it just sends more.
Why store-bought sprays backfire
Repellent sprays kill on contact but scatter the trail and can cause some colonies to split into multiple nests. The ants disappear for a week, then return along a new route. That's the cycle most people know: spray, brief relief, ants back in the same spots every spring and summer.
What source-focused treatment looks like
A licensed technician identifies the species first — pavement ants, odorous house ants, and others behave differently — then follows trails back to entry points and nesting areas. Treatment targets the colony source and the routes ants use to get inside, not just the surfaces where you see them.
One exception worth knowing: large black ants near damp wood may be carpenter ants, a specialty pest that's quoted separately because the treatment is different.
Keeping them gone
Ants are seasonal in Chicago, which is why ongoing protection matters: on Peski's ongoing plan, re-service between scheduled visits is included if covered ants come back. The one-time service carries a 30-day guarantee on the same covered pest.