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Taxonomy terms

Red imported fire ant (Solenposis invicta)

Red imported fire ants are a reportable pest. Although the current area of infestation is in south east Queensland, anyone suspecting they have seen a fire ant nest should contact their state Biosecurity department.

Notice to Queensland residents…

Early detection is essential to control the spread of fire ants. Under the Biosecurity Act 2014, fire ants are a category 1 restricted pest and you are required to notify Biosecurity Queensland if you think you see them. Phone Biosecurity Queensland on 13 25 23 or complete the online yard check report form .

Tend to build nests in disturbed areas, often next to rocks, logs, posts, pavers and paths. Will also build nests in lawns / pasture areas.

It prefers moist, disturbed habitats – areas around human population are ideal. Typically, it  nests outdoors in soil and under rocks / pavers. Sometimes it will nest indoors in wall cavities and plug sockets.

There are two variants of the red important fire ant:

  • Monogynous colonies: Single queen, single nest variant

Monogyne nests can contain up to 250,000 individuals and produce alates (flying ants) that can disperse over 500 m before mating and setting up new colonies. They will defend their territory aggressively against other ants (including other fire ants).

  • Polygynous colonies: Multiple queen, multi-nest variant

Polygynous colonies can contain hundreds of queens and create new nests through budding – a queen takes a few workers and brood to set up a nest nearby. Through this process the polygynous variant can create super-colonies with a mound density of 220 mounds per hectare containing up to 50 million ants.

Both variants are present in the Queensland incursion.

Colour: Shiny red/brown to dark brown (on the abdomen) Size: 2.0 – 6.0 mm (workers are of variable size) Nodes on petiole: 2 Their colour and variable size of worker are key identification features.

Red imported fire ants show a preference for protein / oil, feeding on insects and other animals (alive and dead) and seeds. However, they show a preference for carbohydrate in the cooler months, when presumably they don’t require protein for nest growth. They will tend sap feeding insects to collect honeydew and feed on plant nectaries to get this carbohydrate.

Their nests, once 1-2 years old, become visible as a noticeable mound of dirt which has an open structure with no obvious opening. When the nest is disturbed the ants pour out of the nest in a highly aggressive manner

  • Red important fire ants have a very painful sting, a bit like a bee sting. Individual ants will sting multiple times and with ants swarming over potential victims, they can receive hundreds of stings
  • Like a bee sting, victims can suffer allergic reactions to the sting with potential anaphylactic shock

All fire ant treatments come under the control of the Biosecurity department of the Queensland Government. Biosecurity have an ongoing baiting program to treat infested areas several times a year. They also have a number of teams to treat new infestations reported by the public.

If a homeowner, business owner or farmer suspects they have fire ants on their property, they should submit a report to Biosecurity. They will send out a team to confirm (or otherwise), collect a sample for identification / genetic analysis and carry out a treatment.

However, it can take several weeks for Biosecurity to complete an assessment. If the property owner cannot or doesn’t want to wait, two self-management options are available:

  • DIY fire ant treatment
  • Engage a professional pest manager (who has completed the Biosecurity fire ant training) to carry out the treatment

If you intend to treat the problem yourself, one of the registered fire ant baits should be used. Follow the instructions on the label and apply the bait when the ants are active, making sure the ground is dry and no rain is forecast.

By engaging a pest professional it provide the benefit that they should take care of the treatment and all reporting requirements. Professional Pest Managers are able carry out direct nest injection treatments as well as bait treatments.

Fire ant baits can take a couple of weeks to completely eliminate the nest. However, they do have the advantage that you do not have to find every single nest – by spreading bait over the infested area the ants will find the bait taking it back to the nests.

The general public can help prevent the spread by remaining vigilant and reporting any suspected infestations.

In addition, the prevention measures legislation by the government restrict the movement of soil and materials from the infestation areas.

  • Little fire ants (Wasmannia auropunctata) are another invasive pest with a couple of areas of incursion in Queensland
  • The tropical fire ant (Solenopsis germinata) is also an invasive pest but is now considered established in the Northern Territory and it not being treated by the government

Treatment Notes:

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