A single Queensland fruit fly sparked a major biosecurity alert in Auckland earlier this year, but a venomous snake, a python, scorpions and other creepy crawlers have slipped into New Zealand without fanfare.
There have been 546 biosecurity incursions in the past four years, according to Ministry of Primary Industries (MPI) figures released to Fairfax NZ News and 176 have prompted officials to move to eradicate the pests.
The 54 incursions recorded so far this year include a large diamond python which was destroyed after being found in Auckland and a common brown snake, considered to be the second most venomous land snake in the world, found in Mid-Canterbury this year.
Four years ago an Australian marbled scorpion was found in Mid-Canterbury and another one was found in the Otago Lakes District.
Biosecurity officials did not move to eradicate the scorpions but the MPI said in cases where pests weren't part of a breeding colony or posed no risk to New Zealand's ecosystem, no action was taken, Fairfax reports.
Veronica Herrera, the ministry's response and investigation and diagnostic centre director, said only a small percentage of the organisms found were part of a breeding population.
"And of those, not all present a significant economic or environmental impact as to require action by the ministry."
Foreign lizards, frogs, ants, mites and types of fungus were other invaders dealt with by biosecurity officials.
The single male Queensland fruit fly found in Avondale in May cost taxpayers $1.5 million before officials found no evidence of others in the area. It also led to a verbal spat between Horticulture New Zealand and Primary Industries Minister David Carter about the nation's biosecurity system.