Formica lugubris

Better known as the Northern Hairy Wood Ant.
Hardcastle Crags is quite famous for being a popular home of the Northern Hairy Wood Ant. This breed of ant lives in huge anthills which can be up to six feet tall.
People who know these things say there could be 400 ant nests in the Crags. With an average of half a million inhabitants in each nest that's 200 million individual ants!
They are aggressive little blighters so I keep well away from them - the good news is, when they start rebuilding their nests - Spring has definitely sprung :-)