The Ants You See Are Shoppers
A black garden ant colony lives outdoors, under a slab, a patio or at the foot of a wall. The queen never leaves it. The ants that turn up indoors are workers whose only job is finding food and bringing it back.
So an ant on your worktop is not lost and it is not looking for somewhere to live. It is on an errand, and your house is where the errand has led. Remove what it is collecting and the reason to visit goes with it; kill the ant and the colony sends another one out along the same route.
How One Scout Becomes a Trail
Early foragers wander more or less at random. When one finds something good, it heads home laying a faint chemical scent behind it. Other workers pick up that line and follow it to the food, and each one that succeeds tops the scent up on the way back.
That is why the pattern changes so quickly. At breakfast there is one ant by the kettle. By mid-afternoon there is a neat column from the back door to the sugar bowl, all using exactly the same path, round the same table leg, along the same edge of skirting.
The trail outlives the food. Even after the spill is gone, the scent line stays and workers keep checking it. Wiping the route with ordinary detergent and water removes it, which is why cleaning the path matters as much as cleaning the crumb.
What They Are After
Garden ants have a sweet tooth, but they will take protein and fat too, especially when the colony is raising young. The usual draws are:
- Sugar in any form. Jam, honey, syrup, fruit juice, a sticky ring under a squash bottle.
- Crumbs and grease. The gap beside the cooker, under the toaster, the floor round a high chair.
- Pet food. A bowl left down all day is an easy, reliable source and ants find it fast.
- Bins and recycling. Unrinsed tins, cans and bottles, and the sticky base of a kitchen bin.
- Water. In a dry spell a dripping tap, a damp sink cupboard or a pet's water bowl is worth the trip on its own.
For the kitchen in detail, from worktops to cupboards, see ants in the kitchen.
How They Get In
A worker ant is a few millimetres long, so almost any gap will do. The common ones are the threshold under a back door, the track of a patio door, cracks where a floor meets the wall, gaps round pipes coming through, and weep holes or airbricks at the base of the outside wall. If the nest is under the house or in a wall base, they may come up through a crack in the floor and never be seen outdoors at all.
Sealing these helps later on, but not first. Block the route while the nest is still active and the workers usually just find the next gap along.
Why It Happens When It Does
Ants are active outdoors from spring into autumn and busiest in warm weather, when the colony is growing and needs the most food. A sudden appearance usually means a nest nearby has woken up or grown enough to send foragers further. The way this plays out month by month in a home is covered on the ant season page.
Seeing ants indoors in the middle of winter is different. In an ordinary house that points to a nest in a warm spot under or inside the building, and it is worth a proper look.