Temporal range: 150–0 Ma Jurassic – Recent
|Army ants forming a bridge|
Ants are social insects of the family Formicidae ( /fɔrˈmɪsɨdiː/) and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than 12,500 out of an estimated total of 22,000 species have been classified. They are easily identified by their elbowed antennae and a distinctive node-like structure that forms a slender waist.
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. Larger colonies consist mostly of sterile wingless females forming castes of "workers", "soldiers", or other specialised groups. Nearly all ant colonies also have some fertile males called "drones" and one or more fertile females called "queens". The colonies sometimes are described as superorganisms because the ants appear to operate as a unified entity, collectively working together to support the colony.
Ants have colonised almost every landmass on Earth. The only places lacking indigenous ants are Antarctica and a few remote or inhospitable islands. Ants thrive in most ecosystems and may form 15–25% of the terrestrial animal biomass. Their success in so many environments has been attributed to their social organisation and their ability to modify habitats, tap resources, and defend themselves. Their long co-evolution with other species has led to mimetic, commensal, parasitic, and mutualistic relationships.
Ant societies have division of labour, communication between individuals, and an ability to solve complex problems. These parallels with human societies have long been an inspiration and subject of study. Many human cultures make use of ants in cuisine, medication, and rituals. Some species are valued in their role as biological pest control agents. Their ability to exploit resources may bring ants into conflict with humans, however, as they can damage crops and invade buildings. Some species, such as the red imported fire ant, are regarded as invasive species, establishing themselves in areas where they have been introduced accidentally.
The word ant is derived from ante of Middle English which is derived from æmette of Old English and is related to the Old High German āmeiza, hence the modern German Ameise. All of these words come from West Germanic *amaitjo, and the original meaning of the word was "the biter" (from Proto-Germanic *ai-, "off, away" + *mait- "cut"). The family name Formicidae is derived from the Latin formīca ("ant") from which the words in other Romance languages such as the Portuguese formiga, Italian formica, Spanish hormiga, Romanian furnică and French fourmi are derived. It has been hypothetized that a Proto-Indo-European word *morwi- was used, cf. Sanskrit vamrah, Latin formīca, Greek myrmex, Old Church Slavonic mraviji, Old Irish moirb, Old Norse maurr.
Taxonomy and evolution
The family Formicidae belongs to the order Hymenoptera, which also includes sawflies, bees, and wasps. Ants evolved from a lineage within the vespoid wasps. Fossil evidence indicates that ants were present in the Late Jurassic, 150 million years ago. After the rise of flowering plants about 100 million years ago they diversified and assumed ecological dominance around 60 million years ago. In 1966, E. O. Wilson and his colleagues identified the fossil remains of an ant (Sphecomyrma freyi) that lived in the Cretaceous period. The specimen, trapped in amber dating back to more than 80 million years ago, has features of both ants and wasps. Sphecomyrma probably was a ground forager, but some suggest on the basis of groups such as the Leptanillinae and Martialinae, that primitive ants were likely to have been predators underneath the surface of the soil.
During the Cretaceous period, a few species of primitive ants ranged widely on the Laurasian super-continent (the northern hemisphere). They were scarce in comparison to the populations of other insects, representing only approximately 1% of the entire insect population. Ants became dominant after adaptive radiation at the beginning of the Paleogene period. By the Oligocene and Miocene ants had come to represent 20–40% of all insects found in major fossil deposits. Of the species that lived in the Eocene epoch, approximately one in ten genera survive to the present. Genera surviving today comprise 56% of the genera in