Together with the wasps and bees that are related to them, ants are eusocial insects in the family Formicidae. During the Cretaceous period, vespoid wasps were the ancestors of ants. On the estimated 22,000 species, more than 13,800 have been classified. Their distinctive node-like structure on their slim waists and geniculate (elbowed) antennae make them easy to spot.
Ant colonies can be as small as a few dozen predatory individuals living in small natural cavities to highly organized colonies with millions of members that can occupy large territories. The majority of the sterile, wingless females in larger colonies are workers (ergates), soldiers (dinergates), and other specialized groups. In addition, there are some fertile males known as “drones” and one or more fertile females known as “queens” (gynes) in nearly every ant colony. Because the ants appear to function as a single entity and cooperate to support the colony, the colonies are referred to as superorganisms.
Ants have settled almost every piece of land on Earth. Antarctica and a few isolated or inhospitable islands are the only places where indigenous ants are not found. Ants may have a biomass that is greater than that of wild birds and mammals when they live in moist tropical ecosystems. Social organization as well as their capacity to alter habitats, exploit resources, and defend themselves have been cited as the keys to their success in a wide range of environments. Mimetic, commensal, parasitic, and mutualistic relationships have developed as a result of their extensive co-evolution with other species.