Ants In The House In Winter? The Nest Is Inside

Ants crossing a kitchen counter in an Ohio January did not walk in from the yard. Insects outdoors are shut down at those temperatures. University of Minnesota Extension says it plainly about carpenter ants: finding them indoors in winter means there is a nest inside the building. The ant you are looking at is a resident, not a visitor.

That is a different problem from the one people call about in June, and it is worth knowing which one you have before you buy anything or spray anything.

Why The Calendar Changes What An Ant Means

Ants are cold blooded. Iowa State University Extension makes the inference for you: because carpenter ants are cold blooded, ants active in winter have to be coming from a warmed source. Penn State Extension describes the normal pattern, which is that the ants are inactive through the winter, and then the exception, which is that they will be active if a nest is located in a heated portion of a building. Ohio State University Extension's own carpenter ant fact sheet says the same thing in one line: the ants can continue to be active in wintertime when a nest is in a heated area of the building.

So the summer version of this question and the winter version have different answers. In summer, ants on the counter are usually foragers from a colony in the lawn, under the driveway or in the mulch bed, and the work is mostly outdoors. In winter, something warm and probably damp inside your walls is keeping a colony going while the rest of the yard is asleep.

Which Ant Is It, And Where Would It Be Living?

Three ants account for most winter sightings in Northeast Ohio houses, and each one tends to sit in a different part of the building.

Ohio State's BYGL bulletin adds the Ohio specific note on pavement ants: they come indoors looking for food and may build nests indoors where there is high moisture, including during the winter months. We went through telling the nuisance ants apart from the wood destroying one in carpenter ants in an Ohio house.

Follow The Water, Not The Crumbs

Every one of those sources lands on moisture. Connecticut's integrated pest management guidance tells homeowners to look for sources of moist or rotting wood when hunting a nest site, and the Wisconsin and BYGL descriptions both put indoor nests where the damp is. A heated house in February has a short list of places that are both warm and wet, which is what makes this findable.

• Under the kitchen sink and behind the dishwasher: the cabinet floor, the shutoff valves and the wall behind the trap.
• The bathroom wall: around a tub surround, a shower valve or a toilet supply line, especially on a second floor.
• Window sills and door thresholds: condensation on cold glass runs down and sits in the frame all winter.
• Any ceiling or wall under a roof problem: an ice dam or a plugged gutter wets framing you never see.
• The warm side of the house: around the water heater, the furnace closet, heat registers and the basement ceiling above them.
• The slab: expansion joints, cracks and the seam where a basement floor meets the wall.

Watching where a trail goes is worth more than anything you can buy. The ants are walking a route between a nest and a water or food source, and the end of that route is the part that matters.

Winged Ants At A Winter Window Mean Something Specific

Winged ants on the inside of a window in the middle of winter are a stronger signal than wingless workers. Penn State Extension says that if numerous winged reproductive ants turn up at windows inside the house, they probably came from an indoor nest. A colony only produces those when it is mature, so this is usually a problem that has been running quietly for a while.

It is also the moment people mistake ants for termites, which is an easy mistake and a bad one to act on. Eastern subterranean termites can swarm indoors in winter from a heated structure too. The body tells you which is which, and we laid the comparison out in flying ants or termite swarmers. If the insect has a thick waist, straight antennae and four wings of equal length, stop reading about ants and look at termite control instead. Either way, tape a few to an index card or seal them in a bag before you vacuum them up.

What A Couple Of Ants Does Not Prove

Two honest limits sit on either side of this.

A single ant is not proof of a nest. Minnesota Extension points out that carpenter ant workers get carried indoors with firewood, and those workers cannot start a nest or cause damage in the house. If you brought an armload in from the pile on Saturday and saw one ant on Sunday, that is the likeliest explanation. BYGL is careful in the other direction: a few scouting ants indoors is the first sign of a possible infestation, so it is not nothing either. The pattern decides it. One ant once is firewood. The same wall, the same hour, week after week, is a nest.

Quiet is not proof of the opposite, either. Minnesota notes that a nest sitting somewhere without enough indoor heat or sunshine, a north facing exterior wall for example, stays dormant until spring. A house can hold a colony all winter and show you nothing until April.

What Is Worth Doing Now, And What Can Wait For Spring

Winter is an awkward season for the outdoor half of ant work and a good season for the indoor half. The exterior sealing, the grading, the mulch pulled back off the siding and the branches cut away from the roof all keep until the ground thaws. The nest hunt does not.

• Fix the water first. A nest in damp framing is there because the framing is damp. The leak is the real repair, and it is one you can get done in January.
• Leave the trail alone for a day. Wiping it up scatters the ants and costs you the only map you have. Note where it enters the room and where it disappears.
• Save a few specimens. Identification decides the whole plan, and a photo of a blurry speck decides nothing.
• Do not reach for a residual spray along the baseboards. Ohio State's ant fact sheet is blunt that ant control takes more than spraying a residual insecticide around baseboards, and we went through why that backfires in why ants keep coming back after you spray.
• Understand why baits are the usual answer indoors. Wisconsin extension recommends baiting when the nest is somewhere you cannot reach, such as a wall void, because the workers carry the material back to the colony.
• Do not wait for April on purpose. Utah State University Extension describes odorous house ant subcolonies consolidating into a few overwintering nests in winter, then budding in spring so that many nests exist again by summer. The colony you can find in one place in February is several places by June.

Getting It Looked At In Stark Or Summit County

If the ants are repeating in the same spot, if the numbers are climbing, or if there is sawdust under a window frame, the useful next step is somebody opening up the likely spots and reading the moisture rather than treating a trail. Ant control starts with that inspection, and ants are one of the pests covered by State Shield Essential, the quarterly plan built around breaking egg cycles over four visits a year.

State Termite has worked Stark, Summit, Portage, Wayne and Tuscarawas counties out of North Canton since 1933, and the office answers around the clock. Get a free estimate or call 330-494-6199. If pests come back between treatments, so do we, at no cost.