… this any more:
The winged queen ant collected in the Green River Formation in Wyoming is “about the size of a small bird — about the body mass of a small bird as well,” said Bruce Archibald, the Simon Fraser University researcher who identified it. “It’s pretty impressive.”
Possibly 50 million years old, and similar to giant Eocene ants in Europe. It’s assumed they migrated to North America, but just how is unclear. See abstract here. Some blame a brief bout of prehistoric global warming.