The specimen label
Red imported fire ant
- Name
- Solenopsis invicta, the red imported fire ant, in Queensland’s regulation.
- Length
- 2–6 mm, with ants of various sizes in one nest.
- Colour
- Head and body coppery brown, abdomen darker.
- Temper
- Highly aggressive when disturbed.
- Home range
- Native to South America; now also in the United States, China, Taiwan, Japan, the Philippines and Australia.
- Status
- A category 1 restricted pest under Queensland’s Biosecurity Act 2014.
The size range is the useful clue. Because one nest contains ants of various sizes, small and larger ants turn up together, all in the same copper-and-dark colouring.
The mound, and where it sits
A mound has no obvious entry or exit holes, so there is no doorway to look for. A flat nest is harder: Business Queensland describes it as looking like a small patch of disturbed soil.
Look in the open first. Fire ants are usually found in open areas such as lawns, pastures, roadsides and unused cropland, and can be found next to or under objects such as timber, logs, rocks, pavers or bricks. On acreage that means the house paddock, the verge, the edge of a paved path and the underside of a woodpile.
How a colony grows
- Day 1After a mating flight, a new queen starts a colony and lays 10–20 eggs within 24 hours.
- Days 6–10The eggs hatch, and the queen lays more.
- Months 6–12The colony is producing male and female alates, the sexually mature ants. Newly mated females leave the nest to start more colonies.
A nest left alone for most of a year is therefore no longer one nest’s worth of trouble: by then it can be sending out the queens that start the next ones.
How they travel
The Australian Government’s outbreak page describes fire ants as highly mobile. They can fly up to 5 km and travel over and under the ground. They can raft on waterways after floods or rain, stow away on goods and vehicles, and move with shipping containers and cargo.
People move them too. Queensland has changed its Biosecurity Regulation 2016 to help stop spread through human-assisted movement, and the outbreak page asks that equipment and machinery, slashers, excavators and wheelbarrows included, be cleaned of the soil and other material fire ants like to nest in. The reporting page sets out the zone rules for soil, hay and other carriers.
Why a sighting matters
Fire ants can inflict painful stings on people and animals. In rare cases a sting can cause a severe acute allergic reaction, anaphylaxis; the stings page covers first aid and what a sting does.
The wider stakes are why the law is involved. Business Queensland says that unless they are controlled, fire ants could spread to large areas of Australia and severely damage the local environment, the outdoor lifestyle, and the agricultural and tourism industries.
The record also shows they can be beaten. Fire ants were first detected in Australia in Queensland in February 2001, and they have been eradicated from Australia on eight occasions, six of them in Queensland. Surveillance is ongoing, and treatment and suppression are continuing in the parts of South East Queensland where the ants have been found.
“Report any unusual ants, even if you’re not sure.” Outbreak, Australian Government
That line is the whole of the identification test. Nobody is asked to be certain before they report, and in Queensland the report goes in within 24 hours of the sighting.