Red imported fire ant

Solenopsis invicta

The red imported fire ant (RIFA) nests in open spaces, such as parks and pastures. They can swarm when they are disturbed by people or animals. A mass of angry ants can deliver hundreds of painful stings.

About the red imported fire ant

The RIFA worker ants vary greatly in size, ranging from 2mm to 6mm long. Mostly, the RIFA builds nests in the open. The nest looks like a raised mound of soil, up to 40cm high and 46cm wide. No ants in New Zealand build nests like these. These mounds can damage farm and garden machinery.

In urban areas, RIFA may nest under concrete. Their nests can undermine buildings and paths. Nests may have one or many queens. During flooding, the ants may cling together and form a raft to get to new ground.

The RIFA is quick to develop and reproduce. They can spread up to 40m a year.

Global distribution of red imported fire ant

Why this is a problem for New Zealand?

Economic impact

The ants' painful sting can make harvesting crops impossible. In other countries, people have had to abandon farms and orchards because of the ants. Farmers have needed to remove livestock from places infested with RIFA. Farm equipment can be damaged if a farmer drives over a nest.

They can 'farm' other pests, like aphids and mealy bugs, for their honeydew. Excess honeydew can cause black mould, damaging plants. Red imported fire ants also eat seeds and may attack fruit. They can eat young shoots and roots of plants.

Cost to eradicate

By 2018, Australia had spent AU$320 million over 17 years trying to eradicate the ant from Brisbane.

Environmental impact

They can prey on birds, lizards, and small mammals. They also compete with native lizards, birds, and insects for food.

Social impact

If it became established in New Zealand, this could spell the end of camping, outdoor BBQs, backyard cricket, and outside pets.

The RIFA delivers a painful sting. Some people can have a severe allergic reaction to the sting and can even die. In some countries, people have abandoned playgrounds and parks because of RIFA.

In extreme weather, the ants may seek shelter in people's houses.

Map of New Zealand showing where this pest could establish

How could it get here?

The RIFA is a hitchhiker species. They only need enough room for a queen and a few workers. They can hide in vehicles, shipping containers, machinery, anything with a crevice.

MPI has strict measures in place to limit the chances of RIFA making it through the border.

How to identify the RIFA

The first thing you are likely to see are the mounds made by the ants. Currently, no ant species in New Zealand build large mounds.

  • The ants are reddish-brown.
  • Worker ants range in size from 2mm to 6mm.
  • Males are about 6mm long.
  • Queens are about 8mm to 10mm long (not pictured).
Red imported fire ants in many sizes. Image: Creative Commons Flickr

They are aggressive and, unlike native ants, will swarm towards anyone or anything that disturbs their nest. They move quickly, particularly when it's warm.

Found red imported fire ants?

If you think you've found a fire ant mound:

  • photograph it (and any ants)
  • collect a sample of ants (only if it's safe to do so, do not disturb a nest)
  • call 0800 80 99 66

Note: This information is a summary of RIFA's global distribution and potential impacts to New Zealand.

Last reviewed: