Purple Spider Found Underground

Q: I was digging on my hillside and found a spider that was over five inches in diameter, including the legs. The legs were very stocky and the spider’s body was purple! I believe it was underground. Any idea what it is? 

A: Way cool: a trap door spider! They live in a tube-like, silk-lined burrow underground. The lid to the burrow is made of dry grass clippings and spider silk and is very hard to see. When an insect or a small frog or lizard ventures by, the spider jumps from their tube and grabs its prey, then takes it back underground to eat. There are all sorts of trapdoor spiders in the world but they are mostly overlooked and under-studied because they hide so well.