Ryan McQuoid collected these Manica bradleyi ants in Dorrington, on a bare dirt hillside. He says there were about 30 entrances to the nest. Unlike harvester ants, these ants do not aggressively attack a pine needle or stick inserted into a nest entrance.
According to https://www.antwiki.org/wiki/Manica_bradleyi#Biology “Manica bradleyi, a montane forest species, may use the abundant mycorrhizal roots associated with their nests for food and the larvae may do the actual feeding, returning some of the digested food to the workers.”
Thanks to Dr. Philip Ward for his great identification.