Poisonous Australian redback spiders could be living in Tauranga, experts warn.
The spiders have long lived in New Zealand but AgResearch now fears the spiders are increasing their numbers in populated areas.
Tauranga has been highlighted as an area where colonies were likely be found, along with urban Auckland, Gisborne, Hawke's Bay
and Central Otago.
Research published this month in the international journal Biological Invasions shows conditions in some parts of the country allow the spiders to live and breed.
The spiders tend to live in rocky outcrops, vineyards, grasslands and dry areas under houses.
They are believed to arrive in New Zealand on shipping containers from Australia.
AgResearch scientist Cor Vink said urban areas around major ports were likely habitats.
"Our research shows that surveillance for redback spiders needs to be continued at major ports where cargo from Australia is unloaded."
Successful border control already produces regular interceptions of the redback, as well as interceptions of the invasive brown widow and the western black widow.
Port of Tauranga commercial manager Graeme Marshall said biosecurity was taken seriously at the port.
"We are very conscious as an organisation that there are so many parts of our business that rely on biosecurity being maintained. We work under strict rules that are set by MAF and these are regularly reviewed."
Dr Vink said while it was originally thought the spider could not survive in even moderately wet areas, it was now living in places with relatively high rainfall.
"The research strongly suggests that where there is shelter from rain, particularly in urban areas, redbacks can establish and survive," Dr Vink said.
The spread of the spider is likely to happen as the result of new invasions, rather than from existing populations.
Although they are small, redbacks are highly poisonous - Dr Vink said the spider's bite was "excruciatingly painful".
There have been no deaths from redback spider bites in more than 50 years in Australia, since anti-venom has been available.
The redback spider is easily recognisable by its black body (occasionally brownish) with a prominent red/orange stripe on its abdomen.
The stripe distinguishes it from the false katipo spider.
