Story: Spiders and other arachnids
New Zealand’s spiders are mostly harmless to humans, busily trapping or hunting a vast number of insects. They are spinning their webs everywhere, from the mountains to the coast, and thousands of species have yet to be named.
Full story by Simon Pollard
Main image: Crab spider
The Short Story
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Insect or spider?
Spiders are not insects. They belong to a group called arachnids, which includes mites and scorpions. The biggest difference between the groups is that insects have six legs, while arachnids have eight.
- Most spiders have eight eyes.
- They have jaws with fangs, and eat insects.
- About half of all spiders make silk webs to catch prey. The others are hunters.
- Spider silk is the strongest natural fibre known. It is used to trap and wrap prey, to build nests, as a safety line if the spider falls, and to protect the eggs.
Spiders in New Zealand
New Zealand has about 1,100 named native spider species. They live everywhere, and we are probably never more than a metre away from a spider.
There are two groups: 90% are araneomorphs and 10% are mygalomorphs. The unique New Zealand cave spider has features of both types. It lives in caves, feeding on wētā and blowflies.
Araneomorphs have fangs that move sideways, like your thumb and index finger coming together.
Grey house spider
This is the most common spider in New Zealand, but it arrived from Australia in the 19th century. It makes the cobwebs you see in most homes and gardens.
This is also found in many gardens. Its web often sparkles with morning dew, and insects get stuck in the tiny glue droplets.
The crab spider is a hunter. It waits for an insect to land on a plant, then grabs it, injects venom into its head, and sucks out its insides.
Mygalomorphs are bigger than araneomorphs. They have fangs that move up and down, and they strike downwards at their prey.
The tunnel-web spider has big fangs, and lives among stones and logs. It builds silk tunnels to catch prey, and to hide in.
This makes a tube with a lid (trapdoor). The spider waits under the trapdoor and, when it senses an insect nearby, jumps out and pulls it down the tube.
New Zealand has only one native poisonous spider, and two from Australia.
Katipō means ‘night stinger’ in Maori. Only the female bites. The size of a pea, she is black with a red stripe on her back. Katipō are shy and few New Zealanders see them, let alone get bitten.
This Australian spider lives in dry places around New Zealand.
Also Australian, this lives in cracks, sometimes in house walls. Its bite is less painful than a bee sting.