Well, last year we found a group of these in the sandy soil at the base of a Spruce tree in the back yard. This is the classic ant trap of the Ant Lion.
The adult lays it's eggs on the ground which hatch into a larva known as a "Doodlebug" which builds the trap in sandy soil and waits for an ant to try to cross it. The ant usually slips a little and a few grains of sand roll into the hole. At this signal, the larva kicks up a storm of sand which knocks the ant over, tumbling it into the hole where it is eaten by the doodle bug.
Without digging up the trap one never sees the doodlebug but it is great fun to push a few grains of sand into the hole with a blade of grass and watch the trap erupt like a volcano.
For more insects ........
Insects