We came across two of these mounds in close (less than 10 meters) proximity.
A short video www.flickr.com/photos/brewbooks/4849481045/ I took, really shows how active these are. These ants have a distinctive body, half red, half black.
This may be a Formica obscuripes Thatching Ant mound. I have seen this same mound over in the Yakima area on Umtanum Ridge.
Mount Rainier National Park
Pierce County, Washington, USA
Elevation ~ 1900 meters (5700 feet)
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