Overview
Pavement ants (Tetramorium caespitum) are the most common kitchen ant in Montreal. They nest under concrete slabs, sidewalks, and foundations, and enter homes seeking food. While they pose no structural threat and do not transmit disease, they are a persistent nuisance that can be difficult to eliminate without professional treatment because the colony is located underground, inaccessible to surface sprays.
How to Identify Pavement Ants
- Size: 3–4 mm long — much smaller than carpenter ants (6–13 mm)
- Colour: Dark brown to black
- Head: Parallel grooves (striations) on the head and thorax — visible under magnification
- Antennae: 12-segmented with a 3-segmented club
- Stinger: Present but rarely used against humans
- Behaviour: Form visible trails along baseboards, counters, and walls
- Swarmers: Winged reproductives emerge in late spring and summer
Biology & Colony Structure
- Colony size: 3,000–5,000 workers
- Queens: Typically one queen per colony
- Nesting: Under concrete slabs, sidewalks, foundations, and in soil
- Foraging range: Up to 30 metres from the nest
- Diet: Omnivorous — sweets, proteins, grease, and virtually anything organic
- Activity: Year-round indoors; reduced outdoors in winter
- Territorial: Colonies fight aggressively with neighbouring colonies — large battles visible on sidewalks in spring
Risks
- Food contamination: Ants walk through garbage and contaminated areas before walking across food surfaces
- No structural damage: Pavement ants do not damage wood or other structural materials
- No disease transmission: Not known to transmit diseases to humans
- Nuisance: Persistent trails in kitchens and food storage areas
Signs of Infestation
- Visible trails: Lines of ants along baseboards, counters, and walls — especially in the kitchen
- Soil mounds: Small mounds of fine soil near cracks in concrete, along foundation walls, and between paving stones
- Swarmers: Winged ants emerging from cracks in concrete in late spring
- Foraging ants: Individual ants exploring food sources in the kitchen
- Entry points: Ants entering through gaps around pipes, under doors, and through cracks in the foundation
Prevention
- Store all food in airtight containers
- Clean kitchen counters and floors thoroughly after every meal
- Take out garbage daily and keep bins sealed
- Seal gaps around pipes, under doors, and in the foundation
- Caulk cracks in concrete near the foundation
- Eliminate moisture sources — fix leaky pipes and ensure proper drainage
- Schedule exterior perimeter spray treatment in April before ants become active
Professional Treatment
Professional pavement ant treatment uses gel bait applied along ant trails and near nest entrances, combined with exterior perimeter spray to create a barrier. The gel bait is carried back to the colony by foraging workers, eliminating the entire colony including the queen. Treatment typically requires 1–2 visits. Do NOT use aerosol sprays — they scatter ants and make bait treatment less effective.