That's spiders. All of it. It's acre upon acre of spiders.
Old McDonald had a farm. Keyword being "had." It's the spiders' farm now. Old McDonald's family ran away. McDonald himself was eaten by the spiders because he was old and couldn't outrun them. The family dog is next.
(Seriously though, why would you let your dog walk around in this?)
This is in Australia (which probably means the spiders carry 50 kinds of poison and can kill you just by looking at you funny), the spiders fled to the farmlands when a flood claimed their homes. More photos and info here (but why would you want to see more of this???)