Pest Ants in New Zealand

  • Ants are eusocial insects and belong to the Family Formicidae. They are related to bees and wasps, and all belong to the order Hymenoptera.
  • There are more than 12,000 species worldwide. New Zealand has remarkably few ant species – only around 40 species have been identified. (In Australia nearly 1,300 have been identified).
  • Ants are considered one of the most difficult crawling insect pests to control.

Although the majority of species are not considered pests, the reputation of the main pest ant species has resulted in ants being considered to be the number one global crawling insect pest.

Controlling ants is a challenge, due their sheer numbers and the nest/colony structure – to get lasting control you need to kill the nest, targeting the queen(s) as they are the colony’s egg production unit.

In the domestic situation, they are more of a nuisance, causing food spoilage and stinging/biting homeowners and pets. However, activity in and around electrical wiring is a known cause of house fires.

In commercial situations, they can be a problem in food handling establishments and certain horticultural and agricultural areas.

Perhaps their most significant impact is as environmental pests. Of the world’s top 100 invasive species, five are ants; Argentine ant, big-headed ant, crazy ant, little fire ant and red imported fire ant. These species have been transported around the world by humans and quickly invade new areas, decimating the local ecosystems.

In New Zealand, Argentine ants are a major problem, big-headed ants are present in warmer areas and there are a few spots where crazy ants have been identified.

Fortunately, fire ants are not present in New Zealand.

Working out what type of ant you are looking at is difficult. Identification is very challenging due to their small size.

Successful identification uses size, colour, head & jaw shape and the petiole number and shape. (The petiole is the connection between the thorax and abdomen).

For most homeowners, starting off as to whether it is a black or brown ant is the normal starting point, and that’s how we’ve grouped the species on this page.

If you can catch or kill an individual and look under a magnifying glass you can compare to one of the images above. Click on one of the images above to get additional information to confirm identification.

Here’s a useful article about identifying small brown ants in buildings.

Ants are social insects, with different castes having different roles within the colony. They go through a complete metamorphosis which means after hatching they develop through a number of larval stages before passing through a pupal stage to become an adult.

Ant eggs

Eggs are small white / translucent and oval shaped. They are often stuck to each other in clumps.

Ant larvae

Larvae look like small, segmented maggots, typically white / translucent or cream in colour. They are not particularly mobile and if they need to move they will be carried by workers.

Ant pupae

The pupae are typically cream, oval shaped sacs a bit larger than the adults.

Worker ants

All workers are female. They will often have different roles within the nest, such as looking after the nursery (eggs and larvae), excavating the nest, defending the colony or foraging. Typically they change their roles as they become older – with the older individuals taking on the foraging responsibilities. Workers live between 1-3 years, depending on the species.

Soldier ants

Some species have a specialised soldier caste. Typically they will be larger than workers often with larger heads / jaws. If a species does not have a soldier caste, the defensive responsibilities of the colony are carried out by the workers.

Flying ants

Flying ants or alates, are the winged reproductives – the new kings and queens that leave the nest to mate and start new colonies. These nuptial flight take place in late spring and early summer on hot, humid days. They mate in the air and lose they wings shortly after landing. The males die and the queens move off to find a suitable location to start a new nest.

In some species, there are additional female reproductives (without wings). They support the egg laying of the original queen when the colony gets beyond a certain size or the original queen dies. Such reproductives can also start new nests through the process of budding, when they leave the original nest with a small amount of brood and workers to set up a new nest nearby.

Queen ants

The queen ant is the most important ant in the colony as she lays the eggs. Sometimes there are multiple queens or reproductives in the same colony. To kill the nest it is necessary to kill the queen or all the queens in the colony. The queen is the longest lived individual in the colony and can live for over 20 years.


A nest is a single entity, but a colony may consist of one or more nests. Different species have different colony structures, varying in the number of nests and queens in the colony. There are three general nest structures:

  • Single nest, single queen (monodomous, monogyne)
  • Single nest, multiple queens (monodomous, polygyne)
  • Multiple nests, multiple queens (polydomous, polygene)

The serious pest species – the invasive ants – have a multiple nest, multiple queen colony structure, and it is one of the reasons why they are so successful in invading new areas. Their high reproductive rate allows them to spread rapidly and dominate areas. Over time they can create “super colonies” spread over hundreds of kilometres. This makes it virtually impossible to eradicate invasive ant species from a specific area, as they will re-invade from surrounding areas.


Ants are social insects and display a wide range of amazing and complex behaviours.

When it comes to food, foragers are able to remember good and bad for weeks, even after a single exposure – ants have a long-term food memory!

Although generically called “ant bites”, some species bite, some ants sting and some can do both. Strictly speaking a bite occurs when the ant closes its jaws on the skin and sting is when an individual injects venom from its stinger at the end of its abdomen. It’s the sting that has the potential to cause the most pain. The venom contains a number of chemicals including proteins. It is these proteins that can cause the severe allergic reactions when stung by some species, such as the red imported fire ant, bull ant and green headed ant, and the long lasting itching afterwards. Much like the severe anaphylactic shock caused by bee stings, there are a number of deaths worldwide due to anaphylaxis from ant stings.

For most stings, applying ice to the affected area provides some relief, but for those that suffer severe allergic reactions or experience multiple stings, it is important to seek immediate medical attention.


Professional pest managers succeed where homeowners generally fail in eliminating ant problems as they can access a range of specialist ant control products that are not available to the general public. Combined with their ability to identify the species causing the problem and their knowledge of their nest structure and behaviour, they can design a suitable treatment program.

Typically their treatment will depend on the species and location of the problem

  • House ants
  • Lawn ants
  • Ants in pavers

They will normally use a combination or products, often baits to eliminate the nest and sprays to keep the ants out of the house or treat a particular area. In severe infestations they may need to make more than one visit. If you live in an area infested with one of the invasive species, it is likely you will need regular treatments to keep them under control. For other treatments, the pest managers will often guarantee they will eliminate the problem and offer a warranty or service free period against further ant problems for a set duration.

The main objective in ant control programs is to eliminate the nest. To do this you need to kill the queen or queens. The best way to go about this is to use baits. However, when dealing with invasive species which may infest large areas and have multiple nests as part of the same colony, it is often necessary to use a combination of sprays and baits… and also require regular re-treatment to keep the numbers down (as complete elimination is often impossible).

Although insecticide resistance can be an issue with bed bugs and German cockroaches, there is little evidence of insecticide resistance in ants.

There’s not much you can do to prevent an outdoor ant problem (other than get a professional treatment), but a few of the standard pest prevention techniques will minimise the chances of them becoming a problem indoors.

  • Good hygiene is critical
    • clean away split food and dirty dishes straight away
    • ensure rubbish is put in secure containers
    • don’t leave pet food in bowls on the ground
  • Keep food in sealed containers
  • Seal any small entry holes in the exterior walls / around doors and windows

Remember they will also look to move indoors during the warmer months; during hot dry periods in search of water, or during lengthy periods of heavy rain for a dry nesting site.


Invasive are ants that have been introduced into New Zealand by accident. New Zealand has very few native ant species and these invasive ants quickly out compete the New Zealand ants, and indeed often dominate an environment and completely upset the ecological balance.

Although Argentine ants and big-headed ants are already present in New Zealand, there are a number of other invasive ants that we need to prevent entering and becoming established in New Zealand. 

Our library of pest control articles has further information on pest control ants, ant baits and ant research.

The Landcare Research also has lots of good information on ants.