Taranaki Regional Council has unleashed an unconventional weapon in a bid to control weed growth: Japanese butterflies.
The council released around 200 Honshu white admiral pupae with the hope that the butterflies will attack the Japanese honeysuckle, an invasive weed that smothers and strangles New Zealand native bush.
The butterfly was first imported from Japan in 2010 as a biocontrol agent and has been released in other parts of the country since 2014, after a period of containment and testing.
Steve Ellis, the council's environmental services manager, said the butterfly is one of several biocontrol agents released by the council to control weeds.
The pupae in Taranaki were released at Oākura and Kakaramea just before Christmas, and most had successfully hatched when council workers returned to check on them a week after releasing them.The adult butterflies only live for around a month but lay hundreds of eggs in that time.
Because the caterpillars feed on the leaves of the Japanese honeysuckle and damage the foliage, it is hoped in the long-term they will reduce the weed's growth around the region.
The council now wants to hear from anyone who spots one of the unique-looking butterflies so they can track their spread.
The butterflies are black with white markings on top of their wings. They have a wingspan of around 60mm and the underside of their wings is orange.
Anyone who spots a Honshu white admiral is asked to call the council on 0800 736 222 and ask for a biosecurity environment officer or register their sighting at iNaturalist.nz.