While most of New Zealand’s diverse spider species are harmless, some possess venom that can affect humans. The country has two spider species considered medically significant: the native Katipo and the introduced Redback spider. Bites from these spiders are uncommon, and while they can cause discomfort, serious reactions are rare.
New Zealand’s Venomous Spider Species
The Katipo (Latrodectus katipo) is an endangered native New Zealand spider. The female Katipo typically has a shiny black body with a distinctive red stripe, often bordered in white, running along her abdomen. In some northern areas of the North Island, Katipo females may be entirely black. Females measure 8 to 10 millimeters in body length and are usually found in coastal sand dunes and beaches, building irregular webs among low-growing vegetation, stones, or driftwood. The Katipo is generally shy and non-aggressive.
The Redback spider (Latrodectus hasselti), an Australian import, is related to the Katipo and Black Widow. The adult female Redback is identifiable by her black body with a prominent red or orange stripe on her upper abdomen and an hourglass-shaped red mark underneath. Females can grow up to 15 millimeters long, while males are considerably smaller and not considered a threat. Redbacks prefer dry, sheltered environments, often found in sheds, under outdoor furniture, or in other undisturbed areas around human dwellings. They tend to bite only when disturbed or accidentally trapped.
The White-tailed spider (Lampona cylindrata and L. murina) is characterized by its dark grey to black body with a distinctive white patch at the tip of its abdomen. These spiders are nocturnal hunters that do not build webs for catching prey, instead actively seeking out other spiders. While White-tailed spiders are widespread in New Zealand and their bites can be painful, their venom is not considered medically significant.
Recognizing and Responding to Bites
If bitten by a Katipo or Redback spider, symptoms can include immediate pain at the bite site that may spread and intensify over several hours. Other common reactions include localized or spreading sweating, difficulty breathing, and abdominal cramps. Muscle aches, nausea, vomiting, an increased heart rate, and elevated blood pressure can also occur.
Immediate first aid for a suspected Katipo or Redback spider bite involves cleaning the wound with antiseptic or warm soapy water. Applying an ice pack or cold compress, wrapped in a cloth to prevent direct skin contact, can help reduce pain and swelling. Seek urgent medical attention. Individuals should avoid applying pressure to the wound, using tourniquets, or consuming alcohol after a bite.
For bites from a White-tailed spider, symptoms are generally localized and include pain, a burning sensation, redness, swelling, and itchiness. Simple first aid is usually sufficient: clean the bite area with warm soapy water and apply an ice pack to alleviate discomfort. Medical attention should be sought if the bite area becomes excessively red, painful, blisters, or shows signs of infection.
Preventing Spider Encounters
Minimizing encounters with spiders involves maintaining a tidy environment both indoors and outdoors. Reducing clutter in areas like garages, basements, and storage rooms removes potential hiding spots for spiders. Regularly cleaning and vacuuming around the home, particularly in corners and behind furniture, helps remove webs and egg sacs.
Sealing entry points into the home is another effective measure. Inspect and repair any cracks, holes, or gaps in walls, around windows, and doors. Installing door sweeps and ensuring screens are well-fitted can prevent spiders from entering.
When outdoors, especially where venomous spiders might reside, exercise caution. Clearing overgrown vegetation, woodpiles, and compost reduces outdoor spider habitats. Always check shoes, clothing, and towels before use, particularly if they have been left outside. Wearing gloves when gardening or handling materials in sheds provides an additional layer of protection.