Although the majority of ant 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, big headed, crazy, little fire and red imported fire ant. These species have been transported around the world by humans and quickly invade new areas, decimating the local ecosystems.
Ants getting into food in homes and businesses is more of a nuisance and issue of contamination, as they are not known to spread disease. However, contamination is a serious issue for food management businesses, as no-one wants ants in their food!
However, a couple of ant species do deliver very painful stings, which hurt at the time and can itch for days afterwards. For some people, they can cause allergic reactions which sometimes result in anaphalactic shock which requires urgent medical intervention. In Australia, there have been a few deaths as a result of bull ant stings.
It is important to note that although ants bite (grab on to you with their jaws), it is their sting that hurts. The sting is a needle organ that is thrust out from their abdomen and injects the venom.
The main stinging ants of concern are native ants – bull ants, green-head ants and green tree ants. Bull ants are the largest ants in Australia and there are several species, some of which have their own common name, such as the bulldog ant or jack jumper ant. They are very aggressive ants with large eyes and good vision. Although their nests aren’t particularly large, even one sting is very painful.
Green-head ants are one of the most common stinging ants in residential areas and are commonly found nesting in lawns. Although their bites are considered ‘only’ moderately painful, their sting area can itch for days afterwards.
Two other ants worth a mention are the green tree ant and red imported fire ant. Green tree ants are found in the tropical parts of Australia and then can spray irritant chemicals from their abdomen – often when they bite these chemicals are sprayed into the bite site. Red imported fire ants are an invasive pest now well established in southeast Queensland and northern NSW, despite an active Government control program. These ants have the potential to decimate the environment and change our way of life – they are very aggressive and deliver multiple painful stings. Like a bee sting, these can cause allergic reactions, including anaphalaxis which can result in death.
There are over a 1,000 ant species in Australia but only a few of these are considered as pest ants. It is not particularly scientific, but for many people it is easy to use colour to help distinguish the different types of ants. Here we group the main pest ants in to either black ants or brown ants.
Many of the pest ants in Australia and indeed around the world are invasive ants. Invasive are ants that have been introduced into Australia from another country by accident. They are also called tramp ants and can cause significant economic and ecological damage.
Invasive ants have some common features – they all have rapid rates of reproduction and form multi-queen, multi-nest colonies that are capable or outcompeting local ant species and taking over large areas. Some of the worst invasive ants globally are also present in Australia and include the Argentine ant, big-headed ants (coastal brown ant), fire ants (various species) and white-footed ant.
Dr Ben Hoffman provides a summary of the fight against exotic invasive ants in Australia.
An invasive ant which is becoming more of a significant global threat is the Asian needle ant. Although not yet present in Australia, the climate conditions in Australia would be ideal for its establishment.
Red imported fire ants are considered one of the worst invasive ant species. Not only do they have a significant environmental impact, but they are a serious health risk (with their painful stings and chances of severe allergic reaction) and will have a serious negative impact on animal husbandry and agriculture. If they become established in Australia they will significantly impact the Australian way of life. There is a National Fire Ant Eradication Program in an attempt to prevent their spread. Unfortunately they are spreading in southeast Queensland and are now in northern New South Wales.
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. The queen is the most important caste in the nest as she lays all the eggs. 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.
Eggs are small white / translucent and oval shaped. They are often stuck to each other in clumps.
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.
The pupae are typically cream, oval shaped sacs a bit larger than the adults. These are often assumed to be ant eggs to the untrained eye, but they are a lot bigger.
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 can live between 1-3 years, depending on the species.
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 or alates, are the winged reproductives – the new kings and queens that leave the nest to mate and start new colonies. These reproductives leave the nest in large numbers as part of a nuptial flight, which takes 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, additional female reproductives (without wings) are produced. 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.
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, so that the colony loses its egg laying capacity. The queen is the most long-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:
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 even if they are eliminated from a defined area, they will re-invade from surrounding areas.
Understanding the nest / colony structure and likely nesting sites for the ant species causing a pest control problem is essential understanding in deciding on the appropriate ant treatment.
Ants are social insects and display a wide range of amazing and complex behaviours.
From a control point of view, understanding their foraging behaviour and food preferences is important information when deciding on which ant bait to uses in a control program, where to place the ant bait and how much bait to apply.
[Phil to check if there is an article on ant bait application? If not write one]
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.
Most homeowners find it tempting to try and rid of an ant problem with a bit of DIY pest control, but find it frustrating that they often don’t succeed. Often this is because spraying the ants only kills the ones you can see – there are plenty of other ants back in the nest which can replace them and so the problem quickly returns.
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, for example
For ants in the house the primary objective is to eliminate them out of the house and prevent them re-entering the building. For ants in the lawn it is important to kill the nests. For ants digging up pavers a strategy of killing the nest or excluding the ants from the area works well.
Pest managers will normally use a combination of products to get on top of an ant problem. They will often use sprays to keep the ants out of the house or treat a particular area and baits to eliminate the nest.
They use specialist ant sprays to treat areas and around the perimeter of buildings. Sometimes they use repellent sprays which create a “barrier” to prevent entry, sometimes they will use specialist non-repellent sprays. These non-repellent sprays are designed to kill ants that walk over the treated area. In addition they are relatively slow acting (which is a good thing!). This allows the ants that walk over the treated surface pick up some of the insecticide on their body and pass it on to they nest mates during normal contact, therefore magnifying the effect of the treatment.
(For the really technical, you may ask the question about whether insecticide resistance is an issue in ants, making some products less effective? Although insecticide resistance can be an issue with bed bugs and German cockroaches, there is little evidence of insecticide resistance in ants.)
Sometimes when treating large areas, instead of using sprays, pest managers will use insecticide granules (not baits, but insecticide treated sand). These are often used when dealing with coastal brown ants and funnel ants.
To get lasting control it is important to kill the nest or nests causing the problem, which means killing the queen or queens, as they are producing all the eggs. If you can’t find the nest to destroy it physically or through spraying, you need to use ant baits. Although ant baits will kill the nest causing the problem, it won’t stop new ants moving into the area in the future.
In cases of severe infestations pest managers 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.
To get lasting protection from ants is it necessary to eliminate the nest. To do this you need to kill the queen or queens in the nest, as they produce all the eggs. If you don’t kill the queens, the queen can always product more workers to replace any you kill and the nest will recover. The best way to go about eliminating an ant nest is to use baits.
Ant baits consist of an attractive food source and slow acting insecticides. Ants feed on the bait, take it back to the nest and feed it to other members of the nest, including the queen(s). It needs to be slow acting so that it can passed around the nest before the ant realise it’s not good for them. By the time they do, it’s too late. As long as enough bait is applied relative to the size of the nest, small nests should be eliminated in 1-3 days and larger nests within 1-2 weeks. However, one of the tricks in successful ant bait treatments is choosing the best bait for the ant species of concern, as typically different ant species like different food sources – sugar, protein or oil/fat.
When dealing with invasive ants, although baits are very successful in eliminating individual nests, the problem is that there are often a large number of nests in an area, all part of the same colony. Therefore, 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).
More information on pest control for 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.
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.
The best treatment for ants depends on the species and to a degree, depends on where the problem is. Most pest professionals will use of combination of baits (to kill the nest) and specialist ant sprays to prevent the ants coming into the house.
After a professional ant treatment, you should see a big drop in ant numbers after 24 hours, but if baits are being used, it will take longer to kill the nest. Typically, a nest will be completely eliminated with a bait within 3-7 days. However, if it is a major infestation or large colony, it could take up to 2 weeks, and sometimes a second application may be required.
If a spray is being used to keep ants out of the house, it will typically last between 6-12 weeks, depending on the amount of sun and rain it received. However, most professional will provide a longer warranty, sometimes 6 months or more. This will depend on the species, but they can offer a longer warranty as they normally carry out a range of actions, not just a spray to eliminate the ant problem.
Yes and no. To permanently get rid of ants, you need to destroy the nest and this can be done with baits or if you can find the nest, through directly spraying with insecticide. However, there will also be plenty of other ants ready to move into the area. Therefore to keep the yard clear of ants or prevent ants getting into the house, regular treatments will be required.
Ant baits are generally seen as the best (or smartest) and products as they kill the nest. However, it is important to choose the correct ant bait for the species in question – different ant species have different food preferences so its important to choose the bait to match. There are also a range of specialist ant sprays, which are only available to professional pest managers. These are classed as non-repellent sprays. They aren’t designed to repel the ants and create a barrier, rather they create a treated zone which the ants walk on, picking up the insecticide. Not only does this kill the ant in question, but the ant can also transfer the insecticide to other nest mates, magnifying its effect.
Bull ants (bulldog ants, jack jumper ants) are the most dangerous ant in Australia. Not only is their sting extremely painful, but it can cause significant allergic reactions and anaphylaxis. There have been a few deaths as a result.
Red imported fire ants are now fairly well established in southeast Queensland and have been found in northern NSW. It’s sting is a bit like a bee sting, but often a victim will receive multiple stings as the ants swarm over the victim. Like a bee sting, severe allergic reactions can occur – it is estimated that between 0.5 – 2% of victims will experience an anaphylactic shock. Although rare, this can result in death. Although no deaths have been reported in Australia to date, there are one or two deaths a year in the US, where the infested areas are that much larger.
Our library of pest control articles has further information on pest control ants, ant baits and ant research.
The Australian museum also has lots of good information on ants.