Look closely. Can you see 'em? Itty bitty spiders. Hundreds of them on an itty bitty web strong enough to curl up the edges of the mat and built incredibly fast. I'm guessing that an egg sac came in on a pair of shoes? Right as it was ready to hatch? (I had shaken this mat off the day before I found the itty bitties and washed it the week before.)
But kind of amazing.
Now they live in my vacuum.