Depending on the species, an ant colony holds anywhere from a few thousand to several hundred thousand individuals. Supermarket products only eliminate visible workers: the queen stays protected in the nest and keeps laying. How to fix the problem at the source.
Identify the species before acting
The black garden ant (Lasius niger) is the most common in Belgium. It enters through windows and tile joints, drawn by sugar. It's mainly a food nuisance and doesn't damage structures.
The carpenter ant (Camponotus sp.) is larger (6–12 mm), often shiny black. It excavates damp wood to build its nest, not to eat it like termites. The tunnels still weaken roof timbers and window frames: its presence signals a moisture infiltration.
The pharaoh ant (Monomorium pharaonis) is tiny (1.5–2 mm), golden. It nests indoors, behind electrical outlets, in false ceilings, under floorboards. It's the hardest species to eliminate: a colony can hold 300,000 individuals with dozens of queens.
Why spray insecticides fail
A contact spray kills visible workers but triggers a budding response in some species (notably pharaoh ants): sensing a threat, the colony splits. The queen leaves the nest with part of the workforce and starts a new satellite colony. Result: a spreading infestation.
Over-the-counter solutions (sprays, powder barriers) treat the symptom, not the source. The queen, protected deep in the nest, keeps laying uninterrupted throughout the warm season: the visible population rebuilds within weeks.
The reference method for established colonies is bait gel (a transfer insecticide). Workers ingest the bait and carry it back to the queen. Elimination takes 1 to 3 weeks. If the bait is disturbed before that or patience runs out, the method fails.
What you can do yourself
Remove sources of attraction: crumbs, open sugar bowls, food scraps. Ants follow chemical trails (pheromones): cleaning visible trails with soapy water temporarily breaks the trail.
Locate the entry point: follow the column backwards from the kitchen or bathroom to the crack, failing joint or gap under the door. Seal it with food-safe silicone.
Outdoors, a mound of fine soil near the foundations indicates a garden ant nest. Pouring boiling water directly into the mound works on small, shallow colonies, with no guarantee if the colony has spread deeper.
When to call a professional
Professional intervention is recommended if: ants keep coming back despite your efforts for more than 2 weeks, you see winged ants (swarming, a sign of a mature colony ready to multiply), you suspect carpenter ants (excavation in woodwork), or pharaoh ants appear in electrical outlets or bathroom fittings.
Professional treatment targets the queen, not just the visible workers, and for carpenter ants, treats the tunnels alongside the moisture problem that caused them.
Antinox intervenes within 24h with an inspection to identify the species and locate the nest. Without this step, no treatment lasts.
Prevention: the 4 critical points
Tile joints and kitchen/bathroom silicone: redo every 5–7 years. A failing joint is the main entry point for Lasius niger.
Wood in contact with moisture: check window frames, the base of exterior doors and basement beams. Wood at under 12% moisture doesn't attract carpenter ants.
Vegetation against the facade: branches and stems act as a bridge. Leave a 30 cm gap between vegetation and walls.
Food storage: airtight jars for sugar, flour and cereals. Pharaoh ants can get through the thin plastic of original packaging.
Frequently asked questions
Why are there ants in my bathroom?
The bathroom offers two things ants look for: water (leaks, condensation) and warmth (hot water pipes). Pharaoh ants nest especially in bathroom walls, behind outlets and under bathtubs. Seeing them with no obvious food source nearby is a sign of a nest inside the building.
Are carpenter ants as dangerous as termites?
Not in the same way. Termites eat wood, carpenter ants only excavate it to nest. The structural damage is real but slower. The real warning sign is the moisture they indicate: a carpenter ant infestation in roof timbers almost always reveals an infiltration or condensation problem to treat in parallel.
Does white vinegar keep ants away?
Temporarily. Vinegar destroys trail pheromones and disorganises workers for a few hours. It's not a treatment: the colony reorganises quickly. Useful while you identify and seal the entry point, useless as a lasting solution.
Do ants disappear in winter?
Garden ants go dormant when temperatures drop below 10°C. Indoors, with heating on, pharaoh ants stay active all year. If you see ants in your kitchen in January, the nest is inside the building.