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The Saharan silver ant (''Cataglyphis bombycina'') is a species of
insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (ins ...
that lives in the
Sahara Desert , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...
. It is the fastest of the world’s 12,000 known ant species, clocking a velocity of 855 millimetres per second (over ). It can travel a length 108 times its own body length per second, a feat topped only by two other creatures, the Australian tiger beetle '' Cicindela eburneola'' and the California coastal mite '' Paratarsotomus macropalpis''. This is nearly the walking pace of a human being, and compared to its body size would correspond to a speed of about for a tall human runner. Largely due to the extreme high temperatures of their habitat, but also due to the threat of
predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
, the ants are active outside their nest for only about ten minutes per day. The twin pressures of predation and temperature restrict their above-ground activity to within a narrow temperature band between that at which predatory
lizards Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia althou ...
cease activity and the ants' own upper threshold. The ants often traverse midday temperatures around to scavenge corpses of heat-stricken animals. To cope with such high temperatures, the ants have several unique adaptations. When traveling at full speed, they use only four of their six legs. This quadrupedal gait is achieved by raising the front pair of legs. Several other adaptations, including a very high stride frequency, make ''C. bombycina'' one of the fastest-walking animal species in relation to their body size. Keeping track of the position of the sun, the ants are able to
navigate Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
, always knowing the direct route back to their nest, thus can minimize their time spent in the heat. They produce
heat shock proteins Heat shock proteins (HSP) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock, but are now known to also be expressed during other stresses including expo ...
(HSPs), but unlike other animals, they do this not in direct response to heat. Instead, they do this before leaving the nest, so they do not suffer the initial damage when their body temperature rises quickly. These HSPs allow cellular functions to continue even at very high body temperatures. If they did not produce the proteins in anticipation of the extreme heat, they would die before the proteins could have their effect. A few scouts keep watch and alert the
colony In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...
when ant-eating lizards take shelter in their burrows. Then the whole colony, hundreds of ants, leaves to search for food, although they need to complete their work before the temperature reaches , a temperature capable of killing them. In the words of one researcher, the production of this protein "does not reflect an acute response to cellular injury or protein denaturation, but appears to be an adaptive response allowing the organism to perform work at elevated temperatures during temperature changes too abrupt to give the animal an opportunity to benefit from'' de novo'' HSP synthesis," further "the few minutes duration of the foraging frenzy is too short for synthesis of these protective proteins after exposure to heat." This and other adaptations led to the ant being called "one of the most heat-resistant animals known." Its
critical thermal maximum Critical thermal maximum, in zoology, is the temperature for a given species above which most individuals respond with unorganized locomotion, subjecting the animal to likely death.R.W. McDiarmid, 1999 This concept is particularly relevant in perio ...
is . Silver ants are covered on the top and sides of their bodies with a coating of uniquely shaped hairs with triangular cross-sections that keep them cool in two ways. These hairs are highly reflective under visible and near-infrared light, i.e., in the region of maximal solar radiation. The hairs are also highly emissive in the midinfrared portion of the electromagnetic spectrum, where they serve as an antireflection layer that enhances the ants' ability to offload excess heat by thermal radiation, which is emitted from the hot body of the ants to the air. This passive cooling effect works under the full sun. For this, they have inspired research in the field of passive daytime radiative cooling.


References

{{DEFAULTSORT:ant, silver, Saharan Saharan silver ant Hymenoptera of Africa Saharan silver ant silver ant