Wherever there is dry dirt I see these silver dollar sized craters. Usually there are several in the same location. One day I observed one being made. An insect was hidden in the dirt flicking out particles in a circular pattern. I never saw the entire insect, only the front appendages that move the dirt. I asked John if he knew what type of bug was making this trap and he said it was an antlion. He saw them in eastern Washington. I looked this up on the internet and learn that antlions exist in many parts of the world. As I was taking these pictures I saw an ant stuck in one of the craters. The antlion was concealed in the bottom of the pit and was flinging dirt at the ant which made the ant fall down into the crater to be eaten by the insect. Wikipedia has a lot of information about the life cycle of the insect. Yet another amazing critter here in Costa Rica.