Red imported fire ant (Solenposis invicta) in New Zealand

Pest Snapshot - Red Imported Fire Ant

Scientific name: Solenopsis invicta
Identification: Shiny red / brown ant with darker abdomen. Size: 2.0 – 6.0 mm. Create visible nest mounds with no obvious entrance.
Health threat: High
Bite / sting pain: Very painful sting that get create pustules and potential anaphylatic shock
Difficulty to control: Moderate
Diet: Oil and protein
Nest locations: Outdoors under objectives, next to vertical structures in grassed areas, in pastures and lawns
Colony structure: Both single queen, single nest and multi-queen, multi-nest
Main pest season: Spring – Autumn
Indoor/Outdoor pest: Outdoors

Red imported fire ants are not currently present in New Zealand. However, in the early 2000s there was one red imported fire ant incursion in Napier and 2 interceptions at ports in Auckland and Napier.

In the Napier incursion in 2006, a fairly large nest was identified and treated. After 3 years of surveillence and preventative treatments to the surrounding area, the incursion was declared eliminated in 2009.

Red imported fire ant information

Other common names:

RIFA / fire ant.

Invasive / native:

The red imported fire ant, is an and invasive ant, but it is not currently present in New Zealand.

Distribution:

Not currently present in New Zealand (but has invaded Australia).

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

Comprehensive information on where fire ants are found in Australia and New Zealand.

Typical nest location:

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.

Colony size / structure:

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.

New research has uncovered how a supergene explains fire ant colony structure.

Identification:

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.

Food preferences:

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.

Distinguishing features / behaviours:

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.

There are no other ants in New Zealand that build nests like this.

Bite / sting:

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

Treatment and Prevention notes:

If you think you may have spotted a fire ant nest do not try and treated and do not touch it. Take a photo and contact the Ministry for Primary Industries.

Go to the ants page for more species of ants.

Red Imported Fire Ant FAQ

What do fire ants look like?

Fire ants are a shiny red / brown ant, typically with a dark brown / black abdomen. The worker ants come in a range of sizes from 2.0 mm long to a large 6.0 mm long worker, with large heads.

red imported fire ant worker — Large fire ant worker

What does a fire ant nest look like?

Fire ants start to build an obvious nest mound after only a couple of months. They product a mound of dirt with a crispy outer layer, but will no obvious entrance / exit holes. As the nest matures it can grow to 60 cm or in diameter and 30 cm or more high (although sometimes the next can appear as a flat area of bare ground). The mounds will be built in open pasture / areas of lawn in large infestations, but often they will be built next to hard objects – beside logs and tree stumps, fencing, edge of pavements, etc.

The way to confirm identification of a fire ant nes is to probe the mound with a stick – ants will emerge rapidly in great numbers, attacking the stick aggressively.

fire ant nests The distinctive nest mounds made of dirt, of red imported fire ants

How to identify fire ants?

The easiest way to identify fire ants is by spotting their nests. Even after a few months, a nest mount starts to become visible. They produce a mound of dirt, often against a vertical hard objective with no obvious entrance. There are no other ants in Australia that produce nests like this. If you probe the nest with a stick (be careful), the ants will erupt from the nest in an aggressive manner.

As the ants typically forage at ground level amongst the grass, they can be hard to spot… until you get stung! Although it may be diffcult to tell fire ants from some other ant species (to the untrained eye), their aggressive nature and very painful sting is a big giveaway.

Are there fire ants in New Zealand?

No. Fire ants are not currently in New Zealand and the biosecurity teams are regularly inspecting for fire ants to prevent accidental introduction.

Why are fire ants bad for New Zealand?

Red imported fire ants are an invasive species to New Zealand. Without any natural predators and their rapid rate of reproduction, they will spread rapidly. The climate of much of New Zealand, especially the North Island, would allow fire ants to spread quickly if they get introduced without being detected.

If they become established and spread, they will have three big impacts on the New Zealand way of life:

They will seriously impact the ability of people to enjoy grassed areas. Their stings are very painful and each year it is likely there will be a couple of deaths from anaphylactic shock. Areas will need to have regular treatment to keep them fire ant free.
Agricultural and farming areas will be serious impacted – crops will be difficult to harvest and livestock will be affected.
Many native wildlife species will be largely eliminated from infested areas – in particular many invertebrates, lizards and ground dwelling birds.