Problem ants

An invasive ant is an ant species that is outside its home range (introduced) and damages the human or natural environment. There are many introduced ant species in the Pacific region, most of which are harmless to people, agriculture and the environment. However, a number of very invasive ant species can cause serious harm.

In this section you'll find information on:

the serious problems invasive ants cause
what makes these ants so successful and especially
how critical associations with other insects drive their abundance
where these ants are currently found
features of the the ant life cycle and its importance
how to identify the worst invasive ants

We focus on the:

5 worst threat ants to the Pacific and
13 other unwanted ants that cause problems from time to time

Of the 12,000 or so species of ants globally only a few are responsible for damage to economies, environments and people.

Part of the reason these invasive ants are such a problem is the incredibly high numbers they can reach. When invasive ants reach high abundances, they cause harm in three ways:

1) Agriculture: the ants "farm" scale insects, aphids and other sap-sucking bugs, which damage crop plants, reduce yields and spread crop diseases
2) Environment: they can kill or injure local wildlife including birds, crabs, lizards, insects and make it difficult for stock animals like pigs and chickens to feed
3) Society and Culture: many invasive ants sting, bite or spray acid when disturbed. Stings can form blisters and become infected. Even if they don't sting or bite ants can be in such high numbers that people cannot eat, work or sleep because there are always ants crawling all over them.

A bird killed by yellow crazy ants (© Mikhaila Jacoby)

We focus mostly on the biology and impacts of what are considered the 5 worst invasive ant species. These are the yellow crazy ant (Anoplolepis gracilipes), the red imported fire ant (Solenopsis invicta), the African big-headed ant (Pheidole megacephala), the little fire ant (Wasmannia auropunctata) and the Argentine ant (Linepithema humile). These five species are on the International Union for the Conservation for Nature's 100 of the world’s worst invasive alien species list due to the damage they can cause, and their worldwide distributions. These are also the ants that are most commonly targeted in management programmes, because of the problems they cause.

As well as the five worst ants we have selected 13 other unwanted ants that can cause problems from time to time, but much less often than the 5 worst species.

Click on the icons below for a list of the ants in the PIAT that share these features: