In Formica cunicularia, the worker is an ashy grey black color and is usually 4.0–6.5 mm long. The males are found to have a uniformly dark body and are 8.0–9.0 mm long. The queen is yellowish red to dark black and is 7.5–9.0 mm. These ants are predaceous but are often scavengers.
Formica fusca is a dark-bodied species, 4-7 mm long. The workers are large, at 8–10 millimetres (0.3–0.4 in) long. The food is mixed. Feed on aphids, and live both on trees and on herbaceous plants. It feeds on the corpses of insects, but sometimes attacks the living.