What are these craters?

These craters are built by the larvae of the antlion who is also known as a doodlebug. 

With huge claw-like jaws, the antlion sits partially submerged in the sand at the crater bottom and waits for an ant or other insect to fall in the trap.

These pits were found in the dry sandy soil of my barn overhang.

To see an excellent video of an antlion trapping its prey go to Wikipedia.