Social Spiders

 Have you ever noticed when you see one spider you're likely to see another not too long afterwards?

 Picture from Live Science

It's because some species of spiders are very social animals who build webs and live together in large colonies.  Some species can form colonies of up to 50,000 individuals.  Members of other species have also been known to be social within the same family.  They will form smaller colonies, but share webs when feeding together.