Pavement Ants in Missouri: What They Are and How to Control Them

Pavement ants are one of the most widespread ant species in Missouri and are particularly common in suburban and urban settings where concrete surfaces are abundant. If you have ever noticed small dark ants emerging from cracks in your driveway, sidewalk, or patio — or found them trailing along the edge of a concrete slab inside your garage — you have almost certainly seen pavement ants.

Identifying Pavement Ants

Pavement ants (Tetramorium caespitum) are small — 2.5 to 3mm — and dark brown to black with parallel grooves (striations) on the head and thorax that are visible under magnification. They have two nodes between thorax and abdomen and a pair of small spines on the back of the thorax.

The most distinctive sign of pavement ants is small piles of fine soil or sand pushed up through cracks in concrete — this is the excavated material from their nest tunnels beneath the slab. These piles appear at expansion joints, along foundation cracks, and around the base of exterior walls.

Where Pavement Ants Nest

As the name suggests, pavement ants primarily nest under concrete — beneath driveways, sidewalks, patios, garage slabs, and building foundations. They excavate tunnels and chambers in the soil under the concrete and push debris up through any available crack or gap. Colonies can be large — 3,000 to 5,000 workers — and are typically located 2 to 3 feet below the surface.

They enter homes through cracks in the slab, around expansion joints, through gaps around plumbing penetrations, and along the edge where the slab meets the foundation wall. Once inside, they trail along baseboards and walls to reach kitchen and bathroom areas where food and moisture are available.

Seasonal Behavior

Pavement ants are most visible in spring and early summer when colony activity peaks. In spring, neighboring colonies frequently engage in large territorial battles — you may see masses of ants fighting on sidewalks or driveways, which is actually multiple pavement ant colonies fighting over territory. These battles are temporary and harmless, but they indicate high colony density in the area.

Swarmers (winged reproductives) emerge in late spring to early summer, often inside homes when the colony is beneath a heated slab.

Control Approach

Effective pavement ant control addresses both the interior trailing activity and the outdoor colony beneath the concrete:

• Interior bait: Slow-acting bait placed along active interior trails allows workers to carry the product back to the colony beneath the slab. Pavement ants accept protein and grease baits as well as sweet baits.
• Exterior perimeter treatment: Residual insecticide applied along the foundation perimeter and around slab edges creates a barrier that reduces colony foraging into the structure.
• Crack and crevice treatment: Insecticide dust or residual spray applied directly into expansion joints, slab cracks, and gaps around utility penetrations reaches ants using these as entry pathways.
• Exterior colony treatment: When colonies are located in accessible soil areas (not entirely under concrete), direct treatment of the colony site provides faster population reduction.

Like most ant species, pavement ants are best managed with a combination of interior bait and exterior treatment. Contact spray on interior trails without addressing the exterior colony typically provides only temporary relief as new workers continue to enter from the nest beneath the slab.

Frequently Asked Questions

Are pavement ants dangerous? No. Pavement ants are a nuisance pest — they do not sting (they can bite but rarely do), do not cause structural damage, and do not transmit disease. Their primary impact is contaminating food sources they access indoors.

The ant piles reappear after I seal the cracks — why? Sealing visible cracks addresses entry points but not the colony beneath the slab. The ants simply find new cracks or gaps through which to push their excavated soil. Colony treatment is necessary to stop the activity at its source.