Red imported fire ant

How to recognise it

These are the features that identify a red imported fire ant. Each one is described in words so the identification works without the diagram.

1. Reddish-brown head and thorax with a darker abdomen, and workers of clearly varying sizes within one colony.
2. Two nodes on the waist and a two-segmented antennal club.
3. Mounds are dome-shaped, up to about 45 cm across, with no single central opening — this absence of an obvious entrance hole is characteristic.
4. Disturbing a mound produces immediate, coordinated swarming up vertical surfaces followed by near-simultaneous stinging.

What it leaves behind

• Dome mounds in open sunny turf, appearing rapidly after rain.
• Stings producing a burning sensation followed within a day by a distinctive sterile white pustule.

Why an infestation persists

Colonies relocate readily and can contain multiple queens. Stings are medically significant for people with hymenoptera allergy, and the characteristic pustule is a useful retrospective identifier.

Where it occurs

Established across the Southeast and south-central states and parts of California; under federal and state quarantine in much of that range.

Where to look for it

• Open sunny turf, which is where mounds appear first — lawns, playing fields, verges, and the margins of paths.
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• Along irrigation lines and in any consistently damp strip of lawn.
• Around electrical equipment at ground level — pump housings, meter boxes, and junction boxes — which this species enters and damages.
• After heavy rain, look for floating rafts of ants in standing water, which is how colonies relocate.

When you see it, and why

Mounds become conspicuous after rain in spring and autumn, when colonies push fresh soil to the surface, and this is when most stings occur because the mounds are new and unnoticed. Colonies relocate readily, so a mound removed from a lawn frequently reappears several metres away rather than disappearing. In the hottest part of summer foraging shifts to early morning and evening, which is worth knowing before letting children onto turf at dusk.

What getting the identification wrong costs you

Within the established range the mound plus the coordinated swarming response is distinctive, and the error that matters is the opposite one: assuming any stinging ant mound outside the quarantine area is a fire ant. Harvester ants make a superficially similar mound and are ecologically valuable, so destroying them costs something and gains nothing. The cleared vegetation-free disc and the single obvious entrance mark a harvester nest; a fire ant mound has no single opening.

What a professional actually does

Beyond treatment, the part worth paying for is knowing the quarantine rules. Federal and state quarantines restrict movement of soil, sod, and nursery stock out of infested areas, which affects anyone landscaping, selling plants, or moving fill. An operator working in the established range should be able to tell you what those rules mean for your property without being asked twice.