Question: Why are spiders hairy?

Natasha Myhill answered on 15 Nov 2017:

So, for humans, our hair grows out of the skin – they are separate in a way. For spiders, the ‘hairs’ or setae, are a part of the ‘skin’ – they form a hard outer cuticle layer. The use their ‘hairs’ for a number of things – they can sense vibrations, so if a fly lands on their web, they can sense it without even seeing the fly! They also use them for courtship rituals, movement and even smelling!