Conservation officials are concerned invasive Argentine ants may reach Kāpiti Island.
Argentine ants crawling over a trap. Photo: RNZ / Jonathan Mitchell
The ants have been plaguing the Raumati community for several years, but have been particularly bad this year because of the warmer weather.
The Department of Conservation (DOC) said a colony had now been discovered at the mainland departure point for the Kāpiti Island Nature Reserve,which includes a native bird sanctuary.
DOC said it would poison the nest and continue to monitor the area, keeping alert for any possible reinvasion of the area.
Spokesperson Jack Mace said Argentine ants were highly invasive, and letting even one on the island could have disastrous consequences.
"We can't afford to let even one of these invasive insects get across to the nature reserve.
"These ants are tiny, so we insist that anyone travelling to the island to be very vigilant about checking their gear."
He said DOC could eradicate the ants if they reached the island, but robust quarantine measures were the "first line of defence".
The brown ants are 2 to 3 millimetres in length and can bite.
They are a dominant species that are aggressive towards normal ants and other species.
