05 Nov 2008 -
Communication
Weaver ants collaborating to dismember a red ant (the two at the extremities are pulling the red ant, while the middle one cuts the red ant until it snaps)
Ants communicate with each other using pheromones.[53] These chemical signals are more developed in ants than in other hymenopteran groups. Like other insects, ants perceive smells with their long, thin and mobile antennae. The paired antennae provide information about the direction and intensity of scents. Since most ants live on the ground, they use the soil surface to leave pheromone trails that can be followed by other ants. In species that forage in groups, a forager that finds food marks a trail on the way back to the colony; this trail is followed by other ants, these ants then reinforce the trail when they head back with food to the colony. When the food source is exhausted, no new trails are marked by returning ants and the scent slowly dissipates. This behaviour helps ants deal with changes in their environment. For instance, when an established path to a food source is blocked by an obstacle, the foragers leave the path to explore new routes. If an ant is successful, it leaves a new trail marking the shortest route on its return. Successful trails are followed by more ants, reinforcing better routes and gradually finding the best path.[54]
Ants use pheromones for more than just making trails. A crushed ant emits an alarm pheromone that sends nearby ants into an attack frenzy and attracts more ants from further away. Several ant species even use "propaganda pheromones" to confuse enemy ants and make them fight among themselves.[55] Pheromones are produced by a wide range of structures including Dufour's glands, poison glands and glands on the hindgut, pygidium, rectum, sternum and hind tibia.[51] Pheromones are also exchanged mixed with food and passed by trophallaxis, transferring information within the colony.[56] This allows other ants to detect what task group (e.g., foraging or nest maintenance) other colony members belong to.[57] In ant species with queen castes, workers begin to raise new queens in the colony when the dominant queen stops producing a specific pheromone.[58]
Some ants produce sounds by stridulation, using the gaster segments and their mandibles. Sounds may be used to communicate with colony members or with other species.[59][60]
Defence
A weaver ant in fighting position, mandibles wide open
Ants attack and defend themselves by biting and, in many species, by stinging, often injecting or spraying chemicals like formic acid. Bullet ants (Paraponera), located in Central and South America, are considered to have the most painful sting of any insect, although it is usually not fatal to humans. This sting is given the highest rating on the Schmidt Sting Pain Index. The sting of Jack jumper ants can be fatal,[61] and an antivenin has been developed.[62] Fire ants, Solenopsis spp., are unique in having a poison sac containing piperidine alkaloids.[63] Their stings are painful and can be dangerous to hypersensitive people.[64]
Trap-jaw ants of the genus Odontomachus are equipped with mandibles called trap-jaws, which snap shut faster than any other predatory appendages within the animal kingdom.[65] One study of Odontomachus bauri recorded peak speeds of between 126 and 230 km/h (78 - 143 mph), with the jaws closing within 130 microseconds on average. The ants were also observed to use their jaws as a catapult to eject intruders or fling themselves backwards to escape a threat.[65] Before the strike, the ant opens its mandibles extremely widely and locks them in this position by an internal mechanism. Energy is stored in a thick band of muscle and explosively released when triggered by the stimulation of sensory hairs on the inside of the mandibles. The mandibles also permit slow and fine movements for other tasks. Trap-jaws are also seen in the following genera: Anochetus, Orectognathus, and Strumigenys,[65] plus some members of the Dacetini tribe[66], which are viewed as examples of convergent evolution.
Ant mound holes prevent water from entering the nest during rain.
In addition to defence against predators, ants need to protect their colonies from pathogens. Some worker ants maintain the hygiene of the colony and their activities include undertaking or necrophory, the disposal of dead nest-mates.[67] Oleic acid has been identified as the compound released by dead ants that triggers undertaking behaviour in Atta mexicana.[68]
Nests may be protected from physical threats such as flooding and over-heating by elaborate nest architecture.[69][70] Workers of Cataulacus muticus, an arboreal species that lives in plant hollows, respond to flooding by drinking water inside the nest, and excreting it outside.[71]
Learning
Many animals can learn behaviours by imitation but ants may be the only group apart from mammals where interactive teaching has been observed. A knowledgeable forager of Temnothorax albipennis leads a naive nest-mate to newly discovered food by the excruciatingly slow process of tandem running. The follower obtains knowledge through its leading tutor. Both leader and follower are acutely sensitive to the progress of their partner with the leader slowing down when the follower lags, and speeding up when the follower gets too close.[72]
Controlled experiments with colonies of Cerapachys biroi suggest that individuals may choose nest roles based on their previous experience. An entire generation of identical workers was divided into two groups whose outcome in food foraging was controlled. One group was continually rewarded with prey, while it was made certain that the other failed. As a result, members of the successful group intensified their foraging attempts while the unsuccessful group ventured out less and less. A month later, the successful foragers continued in their role while the others moved to specialise in brood care.[73]
Nest construction
Main article: Ant colony
Leaf nest of weaver ants, Pamalican, Philippines
Complex nests are built by many ants, but other species are nomadic and do not build permanent structures. Ants may form subterranean nests or build them on trees. These nests can be found in the ground, under stones or logs, inside logs, hollow stems or even acorns. The materials used for construction include soil and plant matter,[47] and ants carefully select their nest sites; Temnothorax albipennis will avoid sites with dead ants, as these may indicate the presence of pests or disease. They are quick to abandon established nests at the first sign of threats.[74]
The army ants of South America and the driver ants of Africa do not build permanent nests, but instead alternate between nomadism and stages where the workers form a temporary nest (bivouac) from their own bodies, by holding each other together.[75]
Weaver ant (Oecophylla spp.) workers build nests in trees by attaching leaves together, first pulling them together with bridges of workers and then inducing their larvae to produce silk as they are moved along the leaf edges. Similar forms of nest construction are seen in some species of Polyrhachis.[76]
Food cultivation
Main article: Ant-fungus mutualism
Myrmecocystus (Honeypot) ants store food to prevent colony famine.
Most ants are generalist predators, scavengers and indirect herbivores,[13] but a few have evolved specialised ways of obtaining nutrition. 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 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 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 that may harm the fungi.[77]
from wikipedia
Navigation
Foraging ants travel distances of up to 200 metres (700 ft) from their nest[78] and usually find their way back using scent trails. Some ants forage at night. Day foraging ants in hot and arid regions face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants (Cataglyphis fortis) use visual landmarks in combination with other cues to navigate.[79] In the absence of visual landmarks, the closely related Sahara desert ant (Cataglyphis bicolor) navigates by keeping track of direction as well as distance travelled, like an internal pedometer that counts how many steps they take in each direction. They integrate this information to find the shortest route back to their nest.[80] Several species of ants are able to use the Earth's magnetic field.[81] Ants' compound eyes have specialised cells that detect polarised light from the Sun, which is used to determine direction.[82][83] These polarization detectors are sensitive in the ultraviolet region of the light spectrum.[84]
Weaver ants collaborating to dismember a red ant (the two at the extremities are pulling the red ant, while the middle one cuts the red ant until it snaps)
Ants communicate with each other using pheromones.[53] These chemical signals are more developed in ants than in other hymenopteran groups. Like other insects, ants perceive smells with their long, thin and mobile antennae. The paired antennae provide information about the direction and intensity of scents. Since most ants live on the ground, they use the soil surface to leave pheromone trails that can be followed by other ants. In species that forage in groups, a forager that finds food marks a trail on the way back to the colony; this trail is followed by other ants, these ants then reinforce the trail when they head back with food to the colony. When the food source is exhausted, no new trails are marked by returning ants and the scent slowly dissipates. This behaviour helps ants deal with changes in their environment. For instance, when an established path to a food source is blocked by an obstacle, the foragers leave the path to explore new routes. If an ant is successful, it leaves a new trail marking the shortest route on its return. Successful trails are followed by more ants, reinforcing better routes and gradually finding the best path.[54]
Ants use pheromones for more than just making trails. A crushed ant emits an alarm pheromone that sends nearby ants into an attack frenzy and attracts more ants from further away. Several ant species even use "propaganda pheromones" to confuse enemy ants and make them fight among themselves.[55] Pheromones are produced by a wide range of structures including Dufour's glands, poison glands and glands on the hindgut, pygidium, rectum, sternum and hind tibia.[51] Pheromones are also exchanged mixed with food and passed by trophallaxis, transferring information within the colony.[56] This allows other ants to detect what task group (e.g., foraging or nest maintenance) other colony members belong to.[57] In ant species with queen castes, workers begin to raise new queens in the colony when the dominant queen stops producing a specific pheromone.[58]
Some ants produce sounds by stridulation, using the gaster segments and their mandibles. Sounds may be used to communicate with colony members or with other species.[59][60]
Defence
A weaver ant in fighting position, mandibles wide open
Ants attack and defend themselves by biting and, in many species, by stinging, often injecting or spraying chemicals like formic acid. Bullet ants (Paraponera), located in Central and South America, are considered to have the most painful sting of any insect, although it is usually not fatal to humans. This sting is given the highest rating on the Schmidt Sting Pain Index. The sting of Jack jumper ants can be fatal,[61] and an antivenin has been developed.[62] Fire ants, Solenopsis spp., are unique in having a poison sac containing piperidine alkaloids.[63] Their stings are painful and can be dangerous to hypersensitive people.[64]
Trap-jaw ants of the genus Odontomachus are equipped with mandibles called trap-jaws, which snap shut faster than any other predatory appendages within the animal kingdom.[65] One study of Odontomachus bauri recorded peak speeds of between 126 and 230 km/h (78 - 143 mph), with the jaws closing within 130 microseconds on average. The ants were also observed to use their jaws as a catapult to eject intruders or fling themselves backwards to escape a threat.[65] Before the strike, the ant opens its mandibles extremely widely and locks them in this position by an internal mechanism. Energy is stored in a thick band of muscle and explosively released when triggered by the stimulation of sensory hairs on the inside of the mandibles. The mandibles also permit slow and fine movements for other tasks. Trap-jaws are also seen in the following genera: Anochetus, Orectognathus, and Strumigenys,[65] plus some members of the Dacetini tribe[66], which are viewed as examples of convergent evolution.
Ant mound holes prevent water from entering the nest during rain.
In addition to defence against predators, ants need to protect their colonies from pathogens. Some worker ants maintain the hygiene of the colony and their activities include undertaking or necrophory, the disposal of dead nest-mates.[67] Oleic acid has been identified as the compound released by dead ants that triggers undertaking behaviour in Atta mexicana.[68]
Nests may be protected from physical threats such as flooding and over-heating by elaborate nest architecture.[69][70] Workers of Cataulacus muticus, an arboreal species that lives in plant hollows, respond to flooding by drinking water inside the nest, and excreting it outside.[71]
Learning
Many animals can learn behaviours by imitation but ants may be the only group apart from mammals where interactive teaching has been observed. A knowledgeable forager of Temnothorax albipennis leads a naive nest-mate to newly discovered food by the excruciatingly slow process of tandem running. The follower obtains knowledge through its leading tutor. Both leader and follower are acutely sensitive to the progress of their partner with the leader slowing down when the follower lags, and speeding up when the follower gets too close.[72]
Controlled experiments with colonies of Cerapachys biroi suggest that individuals may choose nest roles based on their previous experience. An entire generation of identical workers was divided into two groups whose outcome in food foraging was controlled. One group was continually rewarded with prey, while it was made certain that the other failed. As a result, members of the successful group intensified their foraging attempts while the unsuccessful group ventured out less and less. A month later, the successful foragers continued in their role while the others moved to specialise in brood care.[73]
Nest construction
Main article: Ant colony
Leaf nest of weaver ants, Pamalican, Philippines
Complex nests are built by many ants, but other species are nomadic and do not build permanent structures. Ants may form subterranean nests or build them on trees. These nests can be found in the ground, under stones or logs, inside logs, hollow stems or even acorns. The materials used for construction include soil and plant matter,[47] and ants carefully select their nest sites; Temnothorax albipennis will avoid sites with dead ants, as these may indicate the presence of pests or disease. They are quick to abandon established nests at the first sign of threats.[74]
The army ants of South America and the driver ants of Africa do not build permanent nests, but instead alternate between nomadism and stages where the workers form a temporary nest (bivouac) from their own bodies, by holding each other together.[75]
Weaver ant (Oecophylla spp.) workers build nests in trees by attaching leaves together, first pulling them together with bridges of workers and then inducing their larvae to produce silk as they are moved along the leaf edges. Similar forms of nest construction are seen in some species of Polyrhachis.[76]
Food cultivation
Main article: Ant-fungus mutualism
Myrmecocystus (Honeypot) ants store food to prevent colony famine.
Most ants are generalist predators, scavengers and indirect herbivores,[13] but a few have evolved specialised ways of obtaining nutrition. 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 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 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 that may harm the fungi.[77]
from wikipedia
Navigation
Foraging ants travel distances of up to 200 metres (700 ft) from their nest[78] and usually find their way back using scent trails. Some ants forage at night. Day foraging ants in hot and arid regions face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants (Cataglyphis fortis) use visual landmarks in combination with other cues to navigate.[79] In the absence of visual landmarks, the closely related Sahara desert ant (Cataglyphis bicolor) navigates by keeping track of direction as well as distance travelled, like an internal pedometer that counts how many steps they take in each direction. They integrate this information to find the shortest route back to their nest.[80] Several species of ants are able to use the Earth's magnetic field.[81] Ants' compound eyes have specialised cells that detect polarised light from the Sun, which is used to determine direction.[82][83] These polarization detectors are sensitive in the ultraviolet region of the light spectrum.[84]
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