Invasive spider with potentially sinister bite confirmed in Aotearoa New Zealand

The spider belongs to the Steatoda genus, a group known as false widow spiders because of their resemblance to the infamous black widow (Latrodectus). Until now, four introduced species of Steatoda had been recorded in New Zealand, with Steatoda nobilis becoming the fifth and most medically significant.

The first confirmed sighting was made in November 2024 by Gavin Picknell in Porirua, Wellington, after he uploaded a photo to the citizen science platform iNaturalist. Given the platform’s research-grade observation standards, the sighting was quickly flagged, with a review of earlier photos revealing that S. nobilis was likely present in the area as early as April 2023.

Professor Steven Trewick, an evolutionary ecologist at Te Kunenga ki Pūrehuroa Massey University, led efforts to confirm the spider’s identity by comparing its physical features and analysing DNA from a sample collected in Porirua. His team focused on a commonly used genetic marker and confirmed a match with published international data.

Since the initial Porirua sighting, S. nobilis has also been confirmed in Christchurch, Nelson, Northland and Waikato. It appears to be thriving in urban environments, particularly around gardens and outdoor furniture. It is most often found under plant pots, tarpaulin and in fence crevices, while males are seen at night on exterior walls or the ground.

“Although considered less dangerous than black widows, the venom of Steatoda nobilis contains similar toxins. Particularly concerning is its association with antibiotic-resistant bacteria. Infections resulting from bites don’t always respond to treatment, and that’s a significant medical concern,” Professor Trewick explains.

While not aggressive, the spider will bite defensively. Most bites cause mild symptoms such as swelling, redness and pain. However, some have been linked to more serious effects including tissue necrosis, nausea, hypotension, impaired mobility and secondary bacterial infections that may be resistant to standard antibiotics.

The presence of antibiotic-resistant bacteria associated with these bites is a concern, given as the species becomes more widespread and population density increases, the bite incidents may also rise.

Originally from the Canary Islands and Madeira, S. nobilis has become well established in Europe, North and South America and now New Zealand. A 2019 ecological model predicted the spider could survive in parts of the country; a prediction that has now been proven accurate.

Professor Trewick notes that although humans often unwittingly facilitate the spread of invasive species, not all environments allow them to flourish.

“Climate conditions play a big role for cold-blooded creatures like spiders. But as we’ve found out, the noble false widow has found New Zealand’s cities quite comfortable.”

While the full impact of this spider on native wildlife is yet to be fully understood, Professor Trewick says its arrival reflects broader global patterns.

“This is part of a wider pattern of biodiversity loss and rapid environmental change. Invasive species like this one highlight how globalisation and climate shifts are reshaping our ecosystems, often at the expense of native wildlife.”

Suspected sightings of this spider can be freely uploaded to iNaturalist NZ and help researchers discover the extent of the invasion.