Why are some spiders so hairy?

It appears that some spiders are hairier than others but why is it some spiders need so many hairs covering their bodies and others don’t? 

When we think of hairy spiders, it’s usually a tarantula that comes to mind. The special hairs on a tarantula have a stinging property and they are able to rub their legs together rapidly to project these hairs onto their prey.

But it isn’t just the big spiders that are covered in hairs, in fact, seemingly hairless spiders have hair too – tiny ones that are actually vital to their survival. Under a microscope you would be able to see lots of small hairs covering the legs, which are call trichobothria. Spiders don’t have ears so they use these hairs to gather information about their surroundings, whether the weather is changing, if danger is nearby, or if a tasty snack if lurking around the corner. Small changes in air movement caused by vibrations can be detected up to one ten billionth of a metre. As well as picking up sound, the hairs are also used to small and taste prey. You can often see spiders turning insects with their legs – they are getting a good feel and tasting to check if the unfortunate insect is edible.


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Photograph: Bart van Dorp