Little black ant

How to recognise it

These are the features that identify a little black ant. Each one is described in words so the identification works without the diagram.

1. Extremely small at 1.5 to 2 mm, noticeably smaller than pavement or odorous house ants seen alongside them.
2. Uniform jet black and shiny, with no grooving on the head or thorax.
3. Two nodes on the waist and no spines on the thorax.
4. Workers are all the same size and move in slow, dense trails.

What it leaves behind

• Very fine trails along mortar lines, cabinet edges, and window frames.
• Small craters of fine soil in lawns and beneath objects on the ground.

Why an infestation persists

Colonies have multiple queens and nest in soil, rotting wood, and wall voids. Their small size means they exploit gaps that exclude larger ants, so sealing has to be thorough to matter.

Where it occurs

Widespread across the United States, most commonly reported in the East and South.

Where to look for it

• Mortar joints in brickwork, both inside an attached garage and on the exterior wall.
• The gap where a window frame meets the reveal, and around the frame of a cat flap or letter plate.
• Inside cabinet carcasses, particularly the drilled shelf-pin holes, which are the right size for this species.
• Beneath objects on the ground outdoors — stones, pots, boards — where small soil craters mark nests.
• Rotting timber in fence posts and landscape edging within a few metres of the house.

When you see it, and why

Activity runs from late spring through summer, with indoor trails most common in the warmest months. Colonies are multi-queen and nest in a wide range of sites, so unlike a single-nest species the population does not collapse when one nest is disturbed — which is why activity often appears to move rather than stop.

What getting the identification wrong costs you

Very small dark ants are routinely lumped together, and the distinction that matters is against the pharaoh ant — pale yellow rather than jet black. That one matters because pharaoh ants bud aggressively and, in a multi-unit building, spread between units when handled wrongly. If the tiny ants are pale and you live in an apartment, stop and get the identification confirmed before anyone treats.