The pavement ant, Tetromorium caespitum, is a common pest that nests directly beneath sidewalks, driveways, and other paved surfaces. While they do not cause structural damage, their large foraging trails and ability to invade kitchens make them a persistent problem. Addressing an infestation requires a strategic approach that targets the entire colony, not just the visible workers. This guide focuses on accurate identification, colony eradication, and long-term prevention.
Identifying Pavement Ants and Their Behavior
Pavement ant workers are small, measuring between 2.5 and 4 millimeters in length, and are dark brown to black. A distinguishing feature is the presence of fine, parallel ridges on their head and thorax, visible with magnification.
Their nests are identified by small, crater-shaped mounds of excavated dirt pushed up through cracks in pavement, along curbs, or near foundations. Pavement ants are omnivorous, consuming sweets, grease, seeds, and other insects. Foraging workers establish visible trails leading to and from food sources.
These ants are known for their territorial behavior, often engaging in aggressive battles with adjacent colonies, particularly in the spring. A single colony can contain several thousand individuals, and mature colonies may house multiple queens, leading to rapid population increase. They are also attracted to moisture, sometimes nesting indoors in wall voids or under floors near plumbing.
Eradication Strategies Targeting the Colony
The most effective long-term solution is eliminating the entire colony, including the queen, using slow-acting ant baits. These baits, available in gel, liquid, or granular formulations, contain an active ingredient with delayed action. Worker ants consume the bait and carry it back to the nest to share with the queen, larvae, and other nestmates through trophallaxis.
This transfer ensures the insecticide is distributed throughout the colony, poisoning the reproductive members and brood. Elimination can take several days to a few weeks. Do not use fast-acting or repellent sprays near bait placements, as these chemicals can kill foraging workers before they deliver the toxicant to the nest.
For outdoor colonies, non-repellent insecticide dust can be applied directly into the nest entrance or deep cracks. Non-repellent products are preferable because ants do not detect the poison and carry the dust particles deeper into the nest, preventing the colony from scattering or budding. Granular baits should be placed along foraging trails and near the nest entrance until ant activity ceases.
Immediate Area Treatment and Exclusion
While baits eliminate the source, immediate area treatments stop ants actively foraging indoors or along exterior trails. Diatomaceous Earth (DE) is a fine powder. When ants crawl over food-grade DE, the powder scratches their protective outer exoskeleton, causing them to dehydrate and die.
A light dusting of DE can be applied along baseboards, window sills, and foundation cracks to disrupt trails and create a physical barrier. Boric acid dust can also be used; it functions as a stomach poison if ingested, disrupting the ant’s digestive system. These dusts kill foraging ants on contact but do not eliminate the subterranean colony.
For immediate relief, physically block access points into the structure. Pavement ants enter through small openings around doors, windows, and utility lines. Sealing these entry points with caulk or sealant prevents future access into the home. Cracks where pipes and wires enter the building are common intrusion points and require special attention.
Preventing Future Infestations
Long-term control requires environmental management to make the area less hospitable. Since pavement ants are omnivorous, removing accessible outdoor food sources is necessary. This includes promptly cleaning up spilled food on patios, securing garbage cans with tight-fitting lids, and keeping pet food bowls clean.
Pavement ants are attracted to moisture, so controlling water sources near the foundation discourages nesting. Homeowners should fix leaky spigots and ensure gutters and downspouts direct water away from the building perimeter. Proper drainage prevents soil beneath sidewalks and foundations from becoming overly saturated, which ants find appealing for nest construction.
Maintaining a dry, clear perimeter around the structure discourages harborage. Trimming back vegetation that touches the house eliminates pathways ants use to access the structure. Removing piles of wood, stones, or debris near the foundation eliminates potential nesting sites.