I found these two queens two weeks ago in the country near Sioux Falls, SD. They are both small and black, however one is noticeably larger. They where flying all over. There where lot's of queens flying, but only these two survive. The larger one has ten eggs that should change into larvae any day. She keeps then spread all over, and doesn't seem to take good care of them, unlike my larger Formica cf. subsericea queens. The smaller one with wings has laid two eggs, then ate them. I believe they are in the Formica fusca group. Sorry for the blurry photos.
smaller queen
smaller queen
larger queen
larger queen
