Background

Argentine ants (Linepithema humile) are among the 100 most invasive species on Earth. First discovered in New Zealand in 1990, they are believed to have reached Northland via potted plants, freight or wood and are now found throughout the region, especially in urban areas.

Argentine ants can form super-colonies of immense size and threaten the region’s environment and economy as well as the lifestyle Northlanders enjoy. An aggressive species, Argentine ant bites are not poisonous but can be irritating and cause allergic-type reactions in some people.

In New Zealand, Argentine ants threaten native insects, lizards and native birds, either attacking them directly or by competing for food like nectar and honeydew. Overseas studies have shown that Argentine ants can have a significant negative impact in natural ecosystems, as they affect natural processes from the soil right through to insect communities, and even the pollination of flowering trees.

How do I recognise them?

Argentine ants …

• Are about 2mm to 3mm long and are a pale honey-brown colour (unlike most house ants, which are black).
• Eat sweet things, but also seek out protein (found in meat, eggs, fish), and will consume dead insects and other small animals.
• Travel steadily in defined continuous trails up to five or six ants (or 2cm) wide.
• Walk or swarm over objects, people or animals, rather than skirting around them.
• Like warm, dry places and nest almost anywhere, but especially on the ground under timber, metal or concrete, plant pots, boats, caravans and tents.
• Are excellent infiltrators! Screw-top jars, closed microwaves, stoves and fridges do not always stop them.
• Commonly found on citrus trees along with high numbers of aphids. The ants farm the aphids for honeydew.

If you suspect you have Argentine ants on your property, bring a sample in a well sealed container with your name, address and phone number to the Department of Conservation or the Northland Regional Council:
Northland Regional Council contact details