There are a lot of ants in our yard. Which is OK, they seem to have migrated away from the house. The vinegar massacres we imposed on them may have had something to do with it: forget harsh bug killers, we kept a spray bottle of straight white vinegar beside the kitchen sink and would spray any ants we saw -- they die in one shot. Magic. And a little tragic.
After it rains, the ants come up for air and rebuild their homes. The dirt they excavate is deposited on the surface, and renders our yard like Monument Valley.