These stuctures are nothing but dirt! I thought they were weeds covered with dirt, but no-they're just dirt and they crumble if you touch them (er, sorry about that, ant friends). Aren't they amazing? I want to learn more about what they're called. Up till this, the most complicated thing I've seen from those ants were mounds that looked like volcanoes. I suppose I should call an exterminator, but they don't really bother anyone and I find them so interesting!