Where do the skinny red worms come from that line the lid of my compost bin?

Where do the skinny red worms come from that line the lid of my compost bin?  They aren’t like any of the worms I see when I dig the soil but they are like the ones that hide under the saucers I put under the flower pots.  It is as if they arrive from out of nowhere. 

I wonder sometimes whether worm eggs are added to the packet of compost maker that I sprinkle on top of the bin’s contents to help break it down?  Perhaps the ones under the flower pot saucers are escapees?