I noticed a spider on my bathroom wall last night (not a particularly pretty one, I think you'll agree). It didn't move at all, and I realised I don't actually know how spiders sleep, if indeed they do. So I decided to find out, and since I'm sure that you're all just as interested as I am in this, I decided to share my findings with you. (Just for accuracy, the spider was in fact on a wall, but I've rotated the pictures through 90 degrees just for the convenience of a landscape format.)
The simple answer to the question "do spiders sleep" is, apparently, that nobody really knows. All animals have some sort of circadian rhythm - a daily activity/inactivity cycle. However, nobody's ever done any studies to measure how long spiders spend in each state, and at what times different species do it.
Scientists do know that in cold climates, spiders are able to go into a form of hibernation, where they bring their legs into their body and remain huddled in a shelter for the winter.
It is thought that if they can shut their bodies down for long periods, they may be able to do the same for shorter periods in their daily cycle, which could be thought of as sleep.
So now you know.
Oh, and for the record, it seems that you're not going to swallow any spiders in your sleep
, despite the urband legend telling you otherwise.