Argentine ants Linepithema humile (Mayr) are one of the world's most invasive and problematic ant species. They are very aggressive, and although they are not poisonous, they do bite people.
Unlike other ant species, Argentine ant colonies cooperate with each other, and can combine over winter into super-colonies. They reach enormous numbers, which means they have a huge appetite. It also makes them more aggressive towards other insect populations through their sheer numbers.
What do they look like?
Face of an Argentine ant
The best way to tell Argentine ants from other ants is by their colour and trails. Argentine ants are small (2-3 mm long) and honey-brown in colour, while most other common household ants in New Zealand are black.
Argentine ants are highly active in searching for food and their trails are often five or more ants wide. Unlike most other ants, they climb trees to get to food sources. Often when people start to notice an ant problem around home where there has not been one in the past, it is due to Argentine ants “moving in”.
Did you know that Argentine ants don't smell when squashed?
Because of their sheer numbers, appetite and aggressiveness, Argentine ants can have a massive impact on the natural environment. While they are one of the major household and garden pests, they pose a serious threat to the conservation values of our reserves and natural areas. These threats include:
- eliminating other species of ants
- competing with kiwi for food such as insects and worms
- competing with other native birds and lizards for nectar
- displacing and killing native invertebrates
Where are they?
Argentine ants are now known for many parts of Auckland and Northland, as well as Bay of Plenty, Hawke's Bay, Wellington, Nelson and Christchurch.
Putting out ant bait at Tiritiri Matangi,
an offshore island nature reserve
DOC has Argentine ant programmes in Northland, Auckland, Canterbury and Nelson/Marlborough conservancies, which include a number of joint operations with city and regional councils.
The focus of the programmes is on raising public awareness and advocacy to limit the spread of this invasive species.
DOC performs surveillance of key reserves. Some control operations are carried out at key conservation sites such as Tiritiri Matangi and Bream Head using specifically formulated bait laid by hand.
You can help
It is important to stop the spread of Argentine ants. You can help to ensure that they are not moved around, in particular by:
- checking potted plants for ants before moving
- checking garden soil and bark, and building materials before moving
- checking camping gear, especially when you are moving in and around reserves
- asking your retailer prior to purchasing goods whether they have Argentine ants and if they do, what treatment regime do they have in place to prevent them from spreading?