Formica planipilis

Large red and black ant, although colonies have very polymorphic worker castes. Some workers can be very small. Colonies are very large and nests are thatched mounds often affiliated within a sagebrush. Colonies defended very aggressively. Foraging workers often travel along long trails. The larger workers are generally more commonly seen foraging than are smaller ones. Species is found more commonly on the slopes of the hills in SNARL than in the flatter, wetter areas. This perhaps indicates some habitat segregation with F. haemorrhoidalis (Nonacs).