Overview
Scientific name: Dolomedes spp.
What do they look like?
Large fast-moving spiders with a leg span of six centimetres or more in adult females. Males are somewhat smaller. These spiders are typically pale brown or grayish in colour with yellow bordering around the cephalothorax (the frontal portion of the spider that bears the legs, fangs, and eyes). D. minor typically has a substantial yellowish stripe running lengthwise from the front to the middle of the abdomen (the rear portion of the spider). The stripe is much less extensive and is often absent in D. aquaticus.
Where are they found?
Both species can be found throughout New Zealand. At least one other species of water spider is still to be described and named by scientists. A particularly large species of Dolomedes can be found in the Chathams.
What are their habits?
Nursery web spiders are known for their webs, yet they do not use them to catch prey. The webs of these spiders are a common sight on gorse and other shrubs and are, as the name suggests, literally nurseries for young spiderlings.
During summer, the female nursery web spider can be seen roaming about carrying a large white ball underneath her. This is her egg sac and she carries it everywhere in her fangs until her young are ready to emerge.
When this time comes, she takes the egg sac to the top of a tree or shrub and constructs the nurseryweb. The mother stays close, and during the day can often be found near the base of the plant where she has deposited her young.
Secure inside the nurseryweb, the young spiderlings emerge from the eggsac and remain here for about a week or so before dispersing by ballooning.
The giant Dolomedes schauinslandi is unique to the Chatham Islands. It also builds a nursery web and is believed to have similar habits to D. minor.
Female water spiders are also attentive mothers and construct a protective web for their young. However, this is in amongst river bed rocks and stones instead of the top of shrubs.
Water spiders are remarkable for another reason. Instead of hunting on land, they catch their prey in rivers and streams, and are able to move about freely on the water's surface. They are also more than capable of going underwater. The hairs on the abdomen trap air, allowing the water spider to carry its own oxygen supply when it submerges.
What is their bite like?
Likely to be painful due the large fangs these spiders possess. However, bites appear to be rare and no serious effects have been reported in assocation with bites from either species.