Chudleigh Knighton Heath is a Site of Special Scientific Interest, while narrow-headed ants are a Section 41 species, nationally rare, and near threatened on the IUCN red list of species, the trust said.
A single nest can hold between 1,000 and 5,000 ants, along with one or more breeding queens that can live for as long as 25 years.
Balfour said: “This is the last population of narrow-headed ants in England, and losing even one colony sets back years of careful work by our staff, volunteers and partners.”
Laura Krusin, conservation officer for Buglife’s Moor Invertebrates Project, said the removal of nests could have a “catastrophic impact on the population, putting even more pressure on an already threatened species”.