Auckland's top ant exterminator
Ant Infestation | Coastal Brown Ants
Fed up with ants in your dishwasher and cat food? You're not alone.
The Coastal Brown Ant — also known as the big-headed ant — is one of the world's top 100 invasive species and one of Auckland's most common household pest problems. This ant has two distinct worker types: the larger "guard ant" (or major worker), recognisable by its disproportionately large head and powerful mandibles, and the smaller minor worker. Guard ants are roughly twice the size of minor workers and far less numerous. Both types range in colour from light brown to near black.
Feeding Habits
Coastal Brown Ants are primarily driven by fats and oils, with proteins as a secondary preference. This is why customers most commonly find them inside dishwashers, in pet food bowls, and along kitchen benches — anywhere residual grease and food matter collects.
Habitat & Behaviour
Coastal Brown Ants nest underground, typically in sandy or disturbed soils, and often beneath objects close to the home — think pavers, pot plants, retaining walls, and garden edging. One of the telltale signs of an infestation is small sandy mounds appearing around driveways and pathways as the colony excavates soil from nest entrances.
In Auckland, these ants are particularly prevalent in suburbs with sandy soils, coastal areas including but not limited to Onehunga, Northcote, Point Chevalier and Herne bay. Colonies support multiple queens, which allows them to grow rapidly and split into new nests — a process called budding — making them especially difficult to eliminate without targeting the colony directly.
One unusual behaviour that often surprises homeowners: Coastal Brown Ants are known to consume and repurpose soft bathroom grout as nesting material. If you're finding crumbling grout alongside ant activity, this species is almost certainly the cause.
Threats & Annoyances
Coastal Brown Ants don't sting painfully or cause structural damage, but they more than make up for it in sheer persistence. Their foraging trails through kitchens, bathrooms, and living areas — combined with their habit of contaminating food and destroying grout — make them one of Auckland's most frustrating household pests.
How ACES Treats Coastal Brown Ants
Off-the-shelf sprays rarely work. They kill worker ants on the surface but never reach the queens — and with multiple queens per colony, the infestation simply rebuilds.
At ACES, we use professional-grade oil-based granular baits sourced from leading research companies in Germany and the USA. Worker ants carry the granules back to the nest and share them through the colony, ensuring queens and larvae are targeted at the source. Our approach is species-specific, meaning the bait formulation is matched precisely to the Coastal Brown Ant's dietary preferences — maximising effectiveness and minimising any impact on the surrounding environment.
Every treatment is backed by our Silver Bullet Guarantee.
Are Coastal Brown Ants making your life difficult? Contact ACES today 09 302 1984 and enjoy an ant-free home — fast.