Identifying pharaoh ants
Pharaoh ants are the smallest common ant species you are likely to encounter in BC — workers are 1-2 mm, smaller than a sesame seed. Colour is light yellow to golden-tan with a darker abdomen. They are often described as 'tiny yellow ants.' They run in visible trails that prefer warm locations — behind refrigerators, near dishwasher heat vents, under stoves, along baseboard heaters, and in wall voids adjacent to building mechanical rooms. The combination of tiny size plus yellow colour plus heat preference is reliable ID.
Why pharaoh ants are treatment-resistant
Pharaoh ant colonies have no single queen — a large colony can have hundreds of queens producing eggs simultaneously. When the colony detects chemical pressure (repellent spray, any contact insecticide), it splits into multiple groups, each retaining queens. A colony of 50,000 workers scattered across a building by spray pressure becomes 20 scattered mini-colonies that each grow back to full strength. This is why hospital and restaurant infestations with pharaoh ants are so persistent — every spray treatment makes the problem larger.
Why they are more common in multi-unit buildings
Pharaoh ants thrive in heated multi-unit buildings for two reasons: (1) the warm mechanical core of a building (boiler rooms, laundry, electrical rooms) provides the consistent heat above 25°C they prefer for brood development; and (2) the interconnected wall cavities of strata buildings allow colonies to move through the entire building without encountering outdoor barriers. A single pharaoh ant introduction — via infested produce, a moving box, or a commercial delivery — can colonize an entire 20-unit building within 18-24 months if not detected early.
Correct treatment protocol
- Confirm species (size, colour, heat preference) before any treatment.
- Do not apply spray or any repellent product.
- Deploy sweet-based non-repellent gel bait at all active trails — in every affected unit simultaneously if in a multi-unit building.
- Place bait in warm locations (near heat sources, mechanical rooms, baseboard heaters).
- Maintain bait for 60-90 days — pharaoh ant colonies are large and treatment is slow.
- Monitor and document progress. Decrease in visible activity within 3 weeks confirms bait uptake; zero activity takes 6-12 weeks in established infestations.
- Coordinate strata-wide treatment. Individual unit bait-only treatment fails if adjacent units have active colonies.
Pharaoh ants in commercial and healthcare settings
Pharaoh ants are a significant pest in hospitals and food service environments. In healthcare settings, they have been documented contaminating sterile equipment and IV bags, and are vectors for hospital pathogens including Salmonella and Pseudomonas. BC health authority standards require documented Integrated Pest Management (IPM) plans for any healthcare facility with pharaoh ant activity. The BC Food Premises Regulation also requires pest control for food-handling operations. Professional treatment with documented bait protocol is required — DIY is not appropriate in regulated settings.