There are so many Agaricus species! Folks dwell on the spore color, but they all have the same spore color, lol. I find Agaricus xanthodermus so often it's maddening. They are so prolific and not edible. At least they improve the soil structure for plants. But I come across Agaricus campestris often enough to take a look at all the grass-dwelling Agaricus I see. Even though they can look different under different weather conditions, they do have some distinctive features. I'm looking for Agaricus augustus, but no success so far this year. But mushroom hunters have to be optimistic! Happy mushroom hunting - and eating!