The word "ant" is derived from ante, emete of Middle English, which are derived from Old English. Ants form colonies that range in size from a few dozen predatory individuals living in small natural cavities to highly organised colonies that may occupy large territories and consist of millions of individuals. Ants communicate with each other using pheromones, sounds, and touch. The paired antennae provide information about the direction and intensity of scents. Larger colonies consist mostly of sterile, wingless females forming castes of "workers", "soldiers", or other specialised groups. Most ants nest in soil, but some will nest in wood or wall voids. They choose sites that are close to moisture and food. Ants move their colonies frequently in response to flooding, temperature changes and physical disturbances. Ants attack and defend themselves by biting and, in many species, by stinging, often injecting or spraying chemicals.