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 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.[8] 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.[10] 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.[11] 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 (Solenopsis invicta), are regarded as invasive species, establishing themselves in areas where they have been introduced accidentally.
Most ants are generalist predators, scavengers, and indirect herbivores,[24] but a few have evolved specialised ways of obtaining nutrition. It is believed that many ant species that engage in indirect herbivory rely on specialized symbiosis with their gut microbes [102] to upgrade the nutritional value of the food they collect [103] and allow them to survive in nitrogen poor regions, such as rainforrest canopies.[104] Leafcutter ants (Atta and Acromyrmex) feed exclusively on a fungus that grows only within their colonies. They continually collect leaves which are taken to the colony, cut into tiny pieces and placed in fungal gardens. Workers specialise in related tasks according to their sizes. The largest ants cut stalks, smaller workers chew the leaves and the smallest tend the fungus. Leafcutter ants are sensitive enough to recognise the reaction of the fungus to different plant material, apparently detecting chemical signals from the fungus. If a particular type of leaf is found to be toxic to the fungus, the colony will no longer collect it. The ants feed on structures produced by the fungi called gongylidia. Symbiotic bacteria on the exterior surface of the ants produce antibiotics that kill bacteria introduced into the nest that may harm the fungi.Foraging ants travel distances of up to 200 metres (700 ft) from their nest [106] and scent trails allow them to find their way back even in the dark. In hot and arid regions, day-foraging ants face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants of the genus Cataglyphis such as the Sahara desert ant navigate by keeping track of direction as well as distance travelled. Distances travelled are measured using an internal pedometer that keeps count of the steps taken [107] and also by evaluating the movement of objects in their visual field (optical flow).[108] Directions are measured using the position of the sun.[109] They integrate this information to find the shortest route back to their nest.[110] Like all ants, they can also make use of visual landmarks when available [111] as well as olfactory and tactile cues to navigate.[112][113] Some species of ant are able to use the Earth's magnetic field for navigation.[114] The compound eyes of ants have specialised cells that detect polarised light from the Sun, which is used to determine direction.[115][116] These polarization detectors are sensitive in the ultraviolet region of the light spectrum.[117] In some army ant species, a group of foragers who become separated from the main column may sometimes turn back on themselves and form a circular ant mill. The workers may then run around continuously until they die of exhaustion.
Most ants are generalist predators, scavengers, and indirect herbivores,[24] but a few have evolved specialised ways of obtaining nutrition. It is believed that many ant species that engage in indirect herbivory rely on specialized symbiosis with their gut microbes [102] to upgrade the nutritional value of the food they collect [103] and allow them to survive in nitrogen poor regions, such as rainforrest canopies.[104] Leafcutter ants (Atta and Acromyrmex) feed exclusively on a fungus that grows only within their colonies. They continually collect leaves which are taken to the colony, cut into tiny pieces and placed in fungal gardens. Workers specialise in related tasks according to their sizes. The largest ants cut stalks, smaller workers chew the leaves and the smallest tend the fungus. Leafcutter ants are sensitive enough to recognise the reaction of the fungus to different plant material, apparently detecting chemical signals from the fungus. If a particular type of leaf is found to be toxic to the fungus, the colony will no longer collect it. The ants feed on structures produced by the fungi called gongylidia. Symbiotic bacteria on the exterior surface of the ants produce antibiotics that kill bacteria introduced into the nest that may harm the fungi.Foraging ants travel distances of up to 200 metres (700 ft) from their nest [106] and scent trails allow them to find their way back even in the dark. In hot and arid regions, day-foraging ants face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants of the genus Cataglyphis such as the Sahara desert ant navigate by keeping track of direction as well as distance travelled. Distances travelled are measured using an internal pedometer that keeps count of the steps taken [107] and also by evaluating the movement of objects in their visual field (optical flow).[108] Directions are measured using the position of the sun.[109] They integrate this information to find the shortest route back to their nest.[110] Like all ants, they can also make use of visual landmarks when available [111] as well as olfactory and tactile cues to navigate.[112][113] Some species of ant are able to use the Earth's magnetic field for navigation.[114] The compound eyes of ants have specialised cells that detect polarised light from the Sun, which is used to determine direction.[115][116] These polarization detectors are sensitive in the ultraviolet region of the light spectrum.[117] In some army ant species, a group of foragers who become separated from the main column may sometimes turn back on themselves and form a circular ant mill. The workers may then run around continuously until they die of exhaustion.
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