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108 Nature

FIND OUT MORE. Arthropods 107 • Invertebrates 102

Arachnids

A large group of eight-legged arthropods, arachnids

include spiders, scorpions, ticks, and mites. All scorpions

and spiders are meat-eating hunters. Ticks and mites are

tiny creatures with sucking or biting mouthparts. Most

ticks live as parasites on animals or plants.

HOW DO SPIDERS SPIN SILK?

Spiders produce liquid silk from glands inside their

abdomens. Structures called spinnerets squeeze out the

silk, which the spider then pulls into long threads with

its legs. Most spiders use silk to spin webs and catch

flying prey. Some spiders hunt without using webs.

HOW DO SCORPIONS KILL THEIR PREY?

Scorpions use their pincers to catch and kill prey.

They pounce on insects, spiders, and even mice and

lizards, then use their pincers to tear them to pieces.

The poisonous sting is used to kill only powerful

victims that put up a fight. Scorpions hunt at night

and use mainly touch and smell to sense their prey.

1 MEAL MITE

Some mites are so small that they cannot be seen

with the naked eye. This photograph of a meal

mite was taken with an electron microscope and

magnified many thousands of times. Meal mites

feed on cereals and are often found in kitchens. The

long hairs help the mite to sense its surroundings.

4 PROTECTIVE MOTHER

The female scorpion carries her babies on her back for two to three

weeks to protect them from predators. After their first moult (shedding

of skin), the young leave their mother to hunt on their own. Male and

female scorpions court by performing a synchronized dance. After

mating, the eggs develop inside the mother’s body, so she gives

birth to living young.

4 TARANTULA

Spiders kill or paralyse their prey by biting it with

poisoned fangs. Then they inject digestive juices

into it. Tarantulas are active hunters, pouncing

on prey rather than catching it in a web. Most

tarantulas live in South and Central America.

Jointed legs

enable spider to

move quickly

Grasshopper

immobilized by

spider’s venom

Pedipalps,

used as

feelers

Mouthparts

suck up juices of

half-digested prey

Forward-facing eyes

make it easier to

judge distances

Almost all arachnids live on land. The class Arachnida includes

about 95,000 species, divided into 10 orders:

• Scorpions • Pseudoscorpions • Spiders • Mites and ticks
  • Harvestmen (daddy long legs) • Whip scorpions • Micro-whip
  scorpions • Solifugids (sun spiders) • Ricinuleids • Amblypygids

ARACHNID CLASSIFICATION

arachnids