Spiders are arachnids, not insects. Other members of the arachnid family include scorpions, mites, ticks and harvestmen. Spiders are differentiated from insects because they have 8 legs while insects have only 6. They also, unlike insects, don't have antennae. 

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Spiders are found on every continent of the world except Antarctica and there are around 40,000 different species of them.

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Tarantulas are large and often hairy spiders. The biggest species have been known to kill mice, lizards and birds.

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People usually think of spiders as having eight eyes, but that’s not always true. While most spiders have eight eyes, there are some that only have six, and even some spiders that have fewer. However, they always come in an even number – there are no cyclops spiders!

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Spiders are a hungry bunch, they eat more insects than birds and bats combined.

 

When a spider travels, it always has four legs touching the ground and four legs off the ground at any given moment

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Spiders have blue blood. In humans, oxygen is bound to haemoglobin, a molecule that contains iron and gives blood its red colour. In spiders, oxygen is bound to hemocyanin, a molecule that contains copper, which gives their blood a blue colour.

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A spider’s muscles pull its legs inward, but cannot extend its legs out again. Instead, it must pump a watery liquid into its legs to push them out. A dead spider’s legs are curled up because there is no fluid to extend the legs again.

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Giant trapdoor spiders are considered living fossils because they are similar to spiders that lived over 300 million years ago. They are found in southeastern Asia, China, and Japan and are over 4 inches across, including their legs.