A compound eye is a visual organ found in arthropods such as insects and crustaceans . It may consist of thousands of ommatidia , which are tiny independent photoreception units that consist of a cornea , lens , and photoreceptor cells which distinguish brightness and color. The image perceived by this arthropod eye is a combination of inputs from the numerous ommatidia, which are oriented to point in slightly different directions. Compared with single-aperture eyes , compound eyes have poor image resolution ; however, they possess a very large view angle and the ability to detect fast movement and, in some cases, the polarization of light. Because a compound eye is made up of a collection of ommatidia, each with its own lens, light will enter each ommatidium instead of using a single entrance point. The individual light receptors behind each lens are then turned on and off due to a series of changes in the light intensity during movement or when an object is moving, creating a flicker-effect known as the flicker frequency, which is the rate at which the ommatidia are turned on and off– this facilitates faster reaction to movement; honey bees respond in 0.01s compared with 0.05s for humans.
53-458: Scorpio is the Latin word for scorpion . It most often refers to: The term Scorpio may also refer to: Scorpion see Taxonomy Scorpions are predatory arachnids of the order Scorpiones . They have eight legs and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always ending with
106-614: A stinger . The evolutionary history of scorpions goes back 435 million years . They mainly live in deserts but have adapted to a wide range of environmental conditions, and can be found on all continents except Antarctica . There are over 2,500 described species , with 22 extant (living) families recognized to date. Their taxonomy is being revised to account for 21st-century genomic studies. Scorpions primarily prey on insects and other invertebrates , but some species hunt vertebrates . They use their pincers to restrain and kill prey, or to prevent their own predation. The venomous sting
159-467: A defensive posture. Some species stridulate to warn off predators by rubbing certain hairs, the stinger or the claws. Certain species have a preference for using either the claws or stinger as defense, depending on the size of the appendages. A few scorpions, such as Parabuthus , Centruroides margaritatus , and Hadrurus arizonensis , squirt venom in a narrow jet as far as 1 meter (3.3 ft) to warn off potential predators, possibly injuring them in
212-417: A ladder-like configuration; they contain cysts which produce spermatozoa . Both tubes end in a spermiduct , one on each side of the mesosoma. They connect to glandular symmetrical structures called paraxial organs, which end at the genital orifice. These secrete chitin -based structures which come together to form the spermatophore . The "tail" or metasoma consists of five segments and the telson , which
265-464: A lens focusing light from one direction on the rhabdom , while light from other directions is absorbed by the dark wall of the ommatidium . The mantis shrimp is the most advanced example of an animal with this type of eye. In the other kind of apposition eye, found in the Strepsiptera , each lens forms an image, and the images are combined in the brain. This is called the schizochroal compound eye or
318-529: A sclerotized plate called the tergite . Ventrally , somites 3 to 7 are armored with matching plates called sternites . The ventral side of somite 1 has a pair of genital opercula covering the gonopore . Sternite 2 forms the basal plate bearing the pectines , which function as sensory organs. The next four somites, 3 to 6, all bear pairs of spiracles . They serve as openings for the scorpion's respiratory organs, known as book lungs . The spiracle openings may be slits, circular, elliptical or oval according to
371-492: A scorpion can tolerate high osmotic pressure in its blood. Desert scorpions get most of their moisture from the food they eat but some can absorb water from the humid soil. Species that live in denser vegetation and in more moderate temperatures will drink water on plants and in puddles. A scorpion uses its stinger both for killing prey and defense. Some species make direct, quick strikes with their tails while others make slower, more circular strikes which can more easily return
424-413: A scorpion is in the back of the cephalothorax, just above the esophagus . As in other arachnids, the nervous system is highly concentrated in the cephalothorax, but has a long ventral nerve cord with segmented ganglia which may be a primitive trait. The pedipalp is a segmented, clawed appendage used for prey immobilization, defense and sensory purposes. The segments of the pedipalp (from closest to
477-429: A shelter underneath stones a few centimeters long. Some may use burrows made by other animals including spiders, reptiles and small mammals. Other species dig their own burrows which vary in complexity and depth. Hadrurus species dig burrows as over 2 m (6 ft 7 in) deep. Digging is done using the mouth parts, claws and legs. In several species, particularly of the family Buthidae, individuals may gather in
530-412: A sting. About 25 species (fewer than one percent ) have venom capable of killing a human, which happens frequently in the parts of the world where they live, primarily where access to medical treatment is unlikely. Scorpions appear in art, folklore, mythology, and commercial brands. Scorpion motifs are woven into kilim carpets for protection from their sting. Scorpius is the name of a constellation;
583-454: A transparent gap but use corner mirrors instead of lenses. Good fliers like flies or honey bees, or prey-catching insects like praying mantises or dragonflies , have specialized zones of ommatidia organized into a fovea area which gives acute vision. In the acute zone the eye is flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution. There are some exceptions from
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#1732852373770636-491: A variety of prey though some may be highly specialized; Isometroides vescus specializes on burrowing spiders. Prey size depends on the size of the species. Several scorpion species are sit-and-wait predators , which involves them waiting for prey at or near the entrance to their burrow. Others actively seek them out. Scorpions detect their prey with mechanoreceptive and chemoreceptive hairs on their bodies and capture them with their claws. Small animals are merely killed with
689-616: A very low metabolic rate , and a relatively inactive lifestyle. This enables some to survive six to twelve months of starvation. Most scorpions reproduce sexually, with male and female individuals; species in some genera, such as Hottentotta and Tityus , and the species Centruroides gracilis , Liocheles australasiae , and Ananteris coineaui have been reported, not necessarily reliably, to reproduce through parthenogenesis , in which unfertilized eggs develop into living embryos . Receptive females produce pheromones which are picked up by wandering males using their pectines to comb
742-408: A way that resembles a true compound eye. Asymmetries in compound eyes may be associated with asymmetries in behaviour. For example, Temnothorax albipennis ant scouts show behavioural lateralization when exploring unknown nest sites, showing a population-level bias to prefer left turns. One possible reason for this is that its environment is partly maze-like and consistently turning in one direction
795-491: Is a good way to search and exit mazes without getting lost. This turning bias is correlated with slight asymmetries in the ants' compound eyes (differential ommatidia count). The body of Ophiomastix wendtii , a type of brittle star , was previously thought to be covered with ommatidia, turning its whole skin into a compound eye, but this has since been found to be erroneous; the system does not rely on lenses or image formation. "Dragonfly eyes" (Chinese: 蜻蜓眼 qingting yan ]
848-470: Is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone. This projects an upright image on a specialized retina. The resulting eye is a mixture of a simple eye within a compound eye. Another version is the pseudofaceted eye, as seen in Scutigera . This type of eye consists of a cluster of numerous ocelli on each side of the head, organized in
901-399: Is based on Soleglad and Fet (2003), which replaced Stockwell's older, unpublished classification. Further taxonomic changes are from papers by Soleglad et al. (2005). The extant taxa to the rank of family (numbers of species in parentheses ) are: Scorpions are found on all continents except Antarctica . The diversity of scorpions is greatest in subtropical areas; it decreases toward
954-861: Is into the clades Buthida and Iurida. The Bothriuridae diverged starting before temperate Gondwana broke up into separate land masses, completed by the Jurassic . The Iuroidea and Chactoidea are both seen not to be single clades, and are shown as " paraphyletic " (with quotation marks) in this 2018 cladogram. Chaeriloidea [REDACTED] Pseudochactoidea [REDACTED] Buthoidea [REDACTED] " Iuroidea " (part) Bothriuroidea [REDACTED] " Chactoidea " (part) " Iuroidea " (part) " Chactoidea " (part) Scorpionoidea [REDACTED] Carl Linnaeus described six species of scorpion in his genus Scorpio in 1758 and 1767; three of these are now considered valid and are called Scorpio maurus , Androctonus australis , and Euscorpius carpathicus ;
1007-421: Is not strictly a segment. The five segments are merely body rings; they lack apparent sterna or terga, and become larger distally. These segments have keels, setae and bristles which may be used for taxonomic classification. The anus is at the distal and ventral end of the last segment, and is encircled by four anal papillae and the anal arch. The tails of some species contain light receptors. The telson includes
1060-485: Is subdivided into a broad anterior portion, the mesosoma or pre-abdomen, and a narrow tail-like posterior, the metasoma or post-abdomen. External differences between the sexes are not obvious in most species. In some, the metasoma is more elongated in males than females. The cephalothorax comprises the carapace , eyes, chelicerae (mouth parts), pedipalps (which have chelae , commonly called claws or pincers) and four pairs of walking legs . Scorpions have two eyes on
1113-602: Is the romanization of the Greek σκορπίος – skorpíos , with no native IE etymology (cfr. Arabic ʕaqrab 'scorpion', Proto-Germanic *krabbô 'crab'). Scorpion fossils have been found in many strata , including marine Silurian and estuarine Devonian deposits, coal deposits from the Carboniferous Period and in amber . Whether the early scorpions were marine or terrestrial has been debated, and while they had book lungs like modern terrestrial species,
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#17328523737701166-423: Is then sucked into the gut in liquid form. Any solid indigestible matter (such as exoskeleton fragments) is trapped by setae in the pre-oral cavity and ejected. The sucked-in food is pumped into the midgut by the pharynx , where it is further digested. The waste passes through the hindgut and out of the anus. Scorpions can consume large amounts of food during one meal. They have an efficient food storage organ and
1219-507: Is used for offense and defense. During courtship, the male and female grasp each other's pincers and dance while he tries to move her onto his sperm packet . All known species give live birth and the female cares for the young as their exoskeletons harden, transporting them on her back. The exoskeleton contains fluorescent chemicals and glows under ultraviolet light. The vast majority of species do not seriously threaten humans, and healthy adults usually do not need medical treatment after
1272-414: The grasshopper mouse and desert long-eared bat , which are also immune to their venom. In one study, 70% of the latter's droppings contained scorpion fragments. Scorpions host parasites including mites , scuttle flies , nematodes and some bacteria. The immune system of scorpions gives them resistance to infection by many types of bacteria. When threatened, a scorpion raises its claws and tail in
1325-458: The littoral zone of rivers in Romania, occupy specialized niches. Scorpions range in size from the 8.5 mm (0.33 in) Typhlochactas mitchelli of Typhlochactidae, to the 23 cm (9.1 in) Heterometrus swammerdami of Scorpionidae. The body of a scorpion is divided into two parts or tagmata : the cephalothorax or prosoma , and the abdomen or opisthosoma . The opisthosoma
1378-531: The tundra , high-altitude taiga , and mountain tops. The highest altitude reached by a scorpion is 5,500 meters (18,000 ft) in the Andes, for Orobothriurus crassimanus . As regards microhabitats , scorpions may be ground-dwelling, tree-loving , rock-loving or sand-loving . Some species, such as Vaejovis janssi , are versatile and are found in all habitats on Socorro Island , Baja California , while others such as Euscorpius carpathicus , endemic to
1431-447: The vesicle , which contains a symmetrical pair of venom glands . Externally it bears the curved stinger, the hypodermic aculeus, equipped with sensory hairs. Each of the venom glands has its own duct to convey its secretion along the aculeus from the bulb of the gland to immediately near of the tip, where each of the paired ducts has its own venom pore. An extrinsic muscle system in the tail moves it forward and propels and penetrates with
1484-417: The aculeus, while an intrinsic muscle system attached to the glands pumps venom through the stinger into the intended victim. The stinger contains metalloproteins with zinc, hardening the tip. The optimal stinging angle is around 30 degrees relative to the tip. Most scorpion species are nocturnal or crepuscular , finding shelter during the day in burrows, cracks in rocks and tree bark. Many species dig
1537-596: The body outward) are coxa, trochanter, femur, patella, tibia (including the fixed claw and the manus) and tarsus (moveable claw). A scorpion has darkened or granular raised linear ridges, called "keels" or "carinae" on the pedipalp segments and on other parts of the body; these are useful as taxonomic characters . Unlike those of some other arachnids, the legs have not been modified for other purposes, though they may occasionally be used for digging, and females may use them to catch emerging young. The legs are covered in proprioceptors , bristles and sensory setae . Depending on
1590-458: The chamber to refill. The 7th and last somite does not bear appendages or any other significant external structures. The mesosoma contains the heart or "dorsal vessel" which is the center of the scorpion's open circulatory system . The heart is continuous with a deep arterial system which spreads throughout the body. Sinuses return deoxygenated blood ( hemolymph ) to the heart; the blood is re-oxygenated by cardiac pores. The mesosoma also contains
1643-401: The claws, particularly by large-clawed species. Larger and more aggressive prey is given a sting. Scorpions, like other arachnids, digest their food externally. The chelicerae, which are very sharp, are used to pull small amounts of food off the prey item into a pre-oral cavity below the chelicerae and carapace. The digestive juices from the gut are egested onto the food, and the digested food
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1696-470: The corresponding astrological sign is Scorpio . A classical myth about Scorpius tells how the giant scorpion and its enemy Orion became constellations on opposite sides of the sky. The word scorpion originated in Middle English between 1175 and 1225 AD from Old French scorpion , or from Italian scorpione , both derived from the Latin scorpio , equivalent to scorpius , which
1749-431: The extreme changes in temperature from day to night or between seasons; Pectinibuthus birulai lives in a temperature range of −30–50 °C (−22–122 °F). Scorpions that live outside deserts prefer lower temperatures. The ability to resist cold may be related to the increase in the sugar trehalose when the temperature drops. Some species hibernate . Scorpions appear to have resistance to ionizing radiation . This
1802-600: The eyes. Some Ananteris species can shed parts of their tail to escape predators. The parts do not grow back, leaving them unable to sting and defecate, but they can still catch small prey and reproduce for at least eight months afterward. Scorpions generally prey on insects, particularly grasshoppers , crickets , termites , beetles and wasps . Other prey include spiders, solifugids , woodlice and even small vertebrates including lizards, snakes and mammals. Species with large claws may prey on earthworms and mollusks. The majority of species are opportunistic and consume
1855-767: The late 19th century in Sheerness in England at 51°N, while Paruroctonus boreus lives as far north as Red Deer, Alberta , at 52°N. A few species are on the IUCN Red List ; Lychas braueri is classed as critically endangered (2014), Isometrus deharvengi as endangered (2016) and Chiromachus ochropus as vulnerable (2014). Scorpions are xerocoles , meaning they primarily live in deserts , but they can be found in virtually every terrestrial habitat including high-elevation mountains, caves, and intertidal zones . They are largely absent from boreal ecosystems such as
1908-667: The modern clades Chactoidea and Buthoidea respectively, indicating that the crown group of modern scorpions had emerged by this time. The Scorpiones are a clade within the pulmonate Arachnida (those with book lungs). Arachnida is placed within the Chelicerata , a subphylum of Arthropoda that contains sea spiders and horseshoe crabs , alongside terrestrial animals without book lungs such as ticks and harvestmen . The extinct Eurypterida , sometimes called sea scorpions, though they were not all marine, are not scorpions; their grasping pincers were chelicerae , not homologous with
1961-676: The most basal such as Eramoscorpius were likely still aquatic. Over 100 fossil species of scorpion have been described. The oldest found as of 2021 is Dolichophonus loudonensis , which lived during the Silurian, in present-day Scotland. Gondwanascorpio from the Devonian is among the earliest-known terrestrial animals on the Gondwana supercontinent. Some Palaeozoic scorpions possessed compound eyes similar to those of eurypterids. The Triassic fossils Protochactas and Protobuthus belong to
2014-401: The neural superposition eye (which, despite its name, is a form of the apposition eye). The superposition eye is divided into three subtypes; the refracting , the reflecting , and the parabolic superposition eye. The refracting superposition eye has a gap between the lens and the rhabdom, and no side wall. Each lens takes light at an angle to its axis and reflects it to the same angle on
2067-483: The order Scorpiones in 1837. He divided it into four families, the six-eyed scorpions "Scorpionides", the eight-eyed scorpions "Buthides", the ten-eyed scorpions "Centrurides", and the twelve-eyed scorpions "Androctonides". More recently, some twenty-two families containing over 2,500 species of scorpions have been described, with many additions and much reorganization of taxa in the 21st century. There are over 100 described taxa of fossil scorpions. This classification
2120-494: The other side. The result is an image at half the radius of the eye, which is where the tips of the rhabdoms are. This kind is used mostly by nocturnal insects. In the parabolic superposition eye , seen in arthropods such as mayflies , the parabolic surfaces of the inside of each facet focus light from a reflector to a sensor array . Long-bodied decapod crustaceans such as shrimp , prawns , crayfish and lobsters are alone in having reflecting superposition eyes , which also have
2173-499: The other three are dubious names. He placed the scorpions among his "Insecta aptera" (wingless insects), a group that included Crustacea, Arachnida and Myriapoda . In 1801, Jean-Baptiste Lamarck divided up the "Insecta aptera", creating the taxon Arachnides for spiders, scorpions, and acari (mites and ticks), though it also contained the Thysanura , Myriapoda and parasites such as lice. German arachnologist Carl Ludwig Koch created
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2226-614: The pincers (second appendages) of scorpions. Scorpiones is sister to the Tetrapulmonata , a terrestrial group of pulmonates containing the spiders and whip scorpions. This 2019 cladogram summarizes: Pycnogonida (sea spiders) [REDACTED] Xiphosura (horseshoe crabs) [REDACTED] † Eurypterida (sea scorpions) [REDACTED] ( ticks , harvestmen , etc) [REDACTED] [REDACTED] Araneae (spiders) [REDACTED] Pedipalpi ( whip scorpions , etc) [REDACTED] Recent studies place pseudoscorpions as
2279-534: The poles and equator, though scorpions are found in the tropics. Scorpions did not occur naturally in Great Britain but were accidentally introduced by humans, and have now established a population. New Zealand , and some of the islands in Oceania , have in the past had small populations of introduced scorpions, but they were exterminated. Five colonies of Euscorpius flavicaudis have established themselves since
2332-402: The reproductive system. The female gonads are made of three or four tubes that run parallel to each other and are connected by two to four transverse anastomoses . These tubes are the sites for both oocyte formation and embryonic development. They connect to two oviducts which connect to a single atrium leading to the genital orifice. Males have two gonads made of two cylindrical tubes with
2385-550: The same shelter; bark scorpions may aggregate up to 30 individuals. In some species, families of females and young sometimes aggregate. Scorpions prefer areas where the temperature remains in the range of 11–40 °C (52–104 °F), but may survive temperatures from well below freezing to desert heat. Scorpions can withstand intense heat: Leiurus quinquestriatus , Scorpio maurus and Hadrurus arizonensis can live in temperatures of 45–50 °C (113–122 °F) if they are sufficiently hydrated. Desert species must deal with
2438-472: The sister group of scorpions in the clade Panscorpiones, which together with Tetrapulmonata makes up the clade Arachnopulmonata. The internal phylogeny of the scorpions has been debated, but genomic analysis consistently places the Bothriuridae as sister to a clade consisting of Scorpionoidea and Chactoidea . The scorpions diversified between the Devonian and the early Carboniferous . The main division
2491-408: The species, the legs may have spines and spurs. The mesosoma or preabdomen is the broad part of the opisthosoma. In the early stages of embryonic development the mesosoma consist of eight segments, but the first segment disappear before birth, so the mesosoma in scorpions actually consist of segments 2-8. These anterior seven somites (segments) of the opisthosoma are each covered dorsally by
2544-422: The species. There are thus four pairs of book lungs; each consists of some 140 to 150 thin lamellae filled with air inside a pulmonary chamber, connected on the ventral side to an atrial chamber which opens into a spiracle. Bristles hold the lamellae apart. A muscle opens the spiracle and widens the atrial chamber; dorsoventral muscles contract to compress the pulmonary chamber, forcing air out, and relax to allow
2597-515: The stinger to a position where it can strike again. Leiurus quinquestriatus can whip its tail at a speed of up to 128 cm/s (50 in/s) in a defensive strike. Scorpions may be attacked by other arthropods like ants, spiders, solifugids and centipedes . Major predators include frogs, lizards, snakes, birds, and mammals. Meerkats are somewhat specialized in preying on scorpions, biting off their stingers and being immune to their venom. Other predators adapted for hunting scorpions include
2650-475: The substrate. Males begin courtship by moving their bodies back and forth, without moving the legs, a behavior known as juddering. This appears to produce ground vibrations that are picked up by the female. Compound eye Compound eyes are typically classified as either apposition eyes, which form multiple inverted images, or superposition eyes, which form a single erect image. Apposition eyes can be divided into two groups. The typical apposition eye has
2703-478: The top of the cephalothorax, and usually two to five pairs of eyes along the front corners of the cephalothorax. While unable to form sharp images, their central eyes are amongst the most light sensitive in the animal kingdom, especially in dim light, which makes it possible for nocturnal species to use starlight to navigate at night. The chelicerae are at the front and underneath the carapace. They are pincer-like and have three segments and sharp "teeth". The brain of
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#17328523737702756-405: The types mentioned above. Some insects have a so-called single lens compound eye, a transitional type which is something between a superposition type of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp, Dioptromysis paucispinosa . The shrimp has an eye of the refracting superposition type, in the rear behind this in each eye there
2809-568: Was discovered in the early 1960s when scorpions were found to be among the few animals to survive nuclear tests at Reggane , Algeria. Desert scorpions have several adaptations for water conservation. They excrete insoluble compounds such as xanthine , guanine , and uric acid , not requiring water for their removal from the body. Guanine is the main component and maximizes the amount of nitrogen excreted. A scorpion's cuticle holds in moisture via lipids and waxes from epidermal glands, and protects against ultraviolet radiation . Even when dehydrated,
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