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What are fire ants and why are they so dangerous?

An extreme closeup of a fire ant


Professor Nigel Andrew
23 January 2024

Fire ants are the hottest topic in insect news right now and rightly so. But where do these invasive pests come from and what makes them so dangerous? Southern Cross University’s Professor Nigel Andrew has the answers.

Fire ants are native to South America. They were first observed in Brisbane in 2001, after probably hitching a ride on a ship that docked at the Port of Brisbane.

They are small ants, about 2-6 mm and extremely aggressive. They swarm when disturbed and don’t only hitch rides on ships – they have been known to catch a ride on mulch and trucks. Sometimes they even make rafts of their own bodies to float down waterways!

Copper brown in colour with a darker abdomen, you might see fire ants of various sizes in the one nest. Most queens might fly up to 2km before building a new nest. But some queens can move up to 30km when they fly and have favourable winds.

Image of a fire ant nest
Fire ant nests can look like mounds of dirt. Credit: National Fire Ant Eradication Program

Why is everyone so worried about fire ants?

Fire ants are a very real threat to people and livestock. Fire ant encounters usually involve tens or hundreds of ants, and they swarm. Their sting is extremely painful, especially when they sting all at once. They have killed people (due to anaphylactic shock after being bitten) in the United States, removed livestock from infested paddocks and have decimated entire native ecosystems.

They’re regarded as one of the world’s worst invasive species and although the DPI and National Fire Ant Eradication Program in Australia are working to control these pests, they have crossed the NSW-QLD state line and were found as far south as Ballina on the NSW North Coast in early 2024.

We need to now make quick and decisive decisions to eradicate this pest from south-east Queensland so it cannot spread any further and does not impact all our lives in the future.

Fire ants can build super colonies with multiple queens and millions of ants. Their nests look like mounds of dirt and you might find them on lawns, footpath edges, garden beds or in bushland.

If you find a nest don’t spray it. Photograph it from a safe distance and contact the relevant authorities immediately.

For information about identifying a nest and what to do, see

Image showing proportion of fire ants to a key
Fire ants range between 2 and 6 mm in length and are extremely aggressive. Credit: National Fire Ant Eradication Program

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