Hole

On my way to check my mailbox, I saw this!

A perfect round hole between the stones. I did not try to poke a stick between the bricks.
It looks to me an insect or a whatever tries to come above the ground. because the sand has been worked out, like a mole does.
It's about 1 cm wide. Something round came out. maybe a bumblebee?
Isn't this interesting? I wonder what it was. 

Does somebody have an idea? Please put it in the comments.