A population of rare native butterflies has been discovered on Little Barrier Island in the Hauraki Gulf.
Rats and wasps have reduced the forest ringlets to only small pockets around the country.
Moths and Butterflies Trust spokeswoman Jacqui Knight says five butterflies were spotted on the same day, and it's a clue to what predators are decimating the rare insect's numbers.
"Now that we've discovered it's in good numbers on Great Barrier, we're thinking it could be rats and wasps, because the island is rat-free."
Ms Knight says the forest ringlet is not closely related to any other species of butterfly, and no one expected to find the species on Little Barrier Island.
"We have done an extensive survey of most New Zealand locations where we knew the forest ringlet could be find, so we're absolutely delighted to think that it's somewhere we've never heard of before."