Which ant is in your Marshalltown kitchen? Ant control depends on it

The ground thaws, April rains for most of a week, and a line of small dark ants is working the seam between the counter and the backsplash. Almost everybody reaches for the can under the sink. That reflex is how a trail in one room becomes trails in two by the end of May.

Which ant you have decides what ends it. Three species cover most of what gets into houses around Marshall County, and you can sort them out at the counter without a hand lens.

How do I tell which ant is in my kitchen?

Two checks do most of the work. Crush one and smell your finger, then follow the line to where it leaves the room.

A crushed odorous house ant smells like rotten coconut, or like blue cheese depending on your nose. Unmistakable once you have done it. Pavement ants smell like nothing much. Carpenter ants are big enough that you will not need the test.

The trail matters as much as the ant. A line running along the counter edge and disappearing behind the sink plumbing is a different problem from a line coming up out of a crack in the basement floor, and both differ from a few large ants crossing the floor one at a time, late at night, with no trail at all.

Odorous house ants, the small dark ants in a line on the counter

Small, dark brown to black, no sting, moving in a steady line rather than wandering. These are the ants most Marshalltown kitchens get, and the season is the giveaway. Their nests outdoors are shallow, which is the whole story: under mulch, landscape timbers, patio stones, the flat rock by the downspout. A week of April rain saturates those nests and the colony moves to the driest warm void it can reach. Foundation cracks and window frames are how they get there.

They live on honeydew from aphids outdoors, so a wet stretch that knocks the aphids off the shrubs moves them toward your sugar at the same time the water moves them out of the soil. Indoors they settle into wall voids, under dishwashers, and behind trim near a slow supply line.

For treatment the thing that matters is that one odorous house ant colony runs many queens across many connected nests. There is no single nest to find and destroy, which is why the can of spray behaves the way it does.

Why are ants coming up through my basement floor?

Pavement ants. Also dark and small, but they nest under concrete instead of under mulch, and they leave a tell. Look at the expansion joints in the driveway, the seam where the sidewalk meets the stoop, or the crack in the basement floor, and you will see small piles of granular excavated soil pushed up out of the gap. That is the nest below the slab telling on itself.

They come in through slab joints, plumbing penetrations, and under the bottom plate of a basement wall, which is why pavement ants show up in the laundry room more often than the upstairs kitchen. In spring you sometimes find them locked together in a shifting mat on a warm sidewalk. Two colonies fighting over territory. Harmless, and it tells you there is a nest on each side of that concrete.

Pavement ant colonies generally run one queen in one nest, so they do not split the way odorous house ants do. The problem is reach. The nest sits under the slab, and nothing sprayed on the floor gets to it.

Big black ants in the house usually mean wet wood

Carpenter ants, the biggest ant you will see indoors in Iowa. Black, with a smoothly rounded back when you look at it from the side. They do not eat wood. They hollow galleries out of wood that is wet or has been wet, and the shavings get pushed out through a slit as a small pile of what looks like sawdust with insect parts mixed in.

Where they turn up in the older neighborhoods here follows water. A porch post sitting on concrete that never dries. The sill under a window whose seal failed a few winters back. The band joist below a bathroom with a weeping supply line. The roof edge behind a gutter that has been overflowing at one corner since nobody was last up there. The housing stock around the downtown square runs 80 to 120 years old, and it has all four of those in quantity.

Two signals are worth a same-day call. Large ants trailing indoors after dark, since these forage at night. And winged ants inside in spring, which usually means the nest is in the structure, not a yard stump.

One more worth knowing by name. Pharaoh ants are tiny, pale yellow, indoors year round, and common in apartments and care facilities. If you are looking at very small light-colored ants in January, nothing above applies and neither does anything sold at a hardware store. Sprayed, they scatter worse than any ant here.

Why did spraying the ants make it worse?

Over-the-counter ant sprays are repellent by design. They kill the foragers on the counter, the visible part of the colony and the smallest part of it, and leave a treated band the survivors read as a hostile edge.

An odorous house ant colony answers that pressure by budding. Workers pick up brood and one of the several queens and walk away to start a nest where the pressure is not, which in a house means the next wall void over. One trail becomes two or three, in rooms that never had ants, and each new nest is a working colony. The home page puts it shorter: spray-and-pray makes satellite colonies.

There is a second cost. The workers on that trail were the delivery system for any bait you might use next, and a sprayed surface gets avoided, so the treatment that would have worked now gets refused. You also lost the trail, which was a free map to the nest.

How do you get rid of an ant trail for good?

Bait it, and then leave the trail alone while the bait does the work. Slow-acting matters more than strong. Ants pass liquid food mouth to mouth inside the nest, so a worker that makes it home carries the dose to the queens and the brood. A bait that kills on contact never gets home.

Which means a few things that feel wrong while you are doing them:

• Do not wipe the trail while bait is out. The pheromone line is what routes foragers to it.
• Set the bait beside the trail rather than on it, and near where the line enters the room rather than at the food they found.
• Expect more ants at first. A crowd on the bait is the treatment working.
• Clear the competing food. The ring under the honey jar, the pet bowl left down overnight.

Carpenter ants are the exception. Their diet varies enough that baiting is unreliable, so that job is finding the nest and then dealing with the water that made the wood habitable. Pavement ants coming up through a slab need the nest treated from outside along the concrete edge, not another pass across the basement floor.

What does ant control cost in Marshalltown?

A one-time general pest visit covering ants, spiders and roaches runs $150 - $350 on our pest control cost page, with pest type, infestation size and house size moving the number. That same page describes an ant job as an hour of targeted baiting, which is what it is while the trail is still in one room.

The quarterly plan on that page, $40 - $75 / month, buys a perimeter band that goes down ahead of the April rain instead of after the ants have already found the counter. That math works on a house where ants are an annual April event. If this is the first spring you have seen them, one visit is usually the whole job.

Should I call an ant exterminator, or wait it out?

One trail in a kitchen that has never had ants is worth baiting yourself first. If it goes quiet and stays quiet, that was the whole problem.

The versions that do not resolve on their own: a trail that came back after you sprayed it, trails in more than one room, large ants running after dark, shavings under a window sill, or ants still arriving after the wet stretch has ended and the ground has dried.

If you do call, leave the trail alone until somebody has looked at it. A live line gets followed to the entry point on the first visit. A wiped and sprayed counter turns that into guesswork. Say on the phone what you have already put down, because a treated surface changes what can be baited and how soon. What a visit covers is on the ant section of the home page.