The instrument was primarily used in an ensemble setting well into the 1930s, and although the fad died out at the beginning of the 1930s, the instruments that were developed for the orchestra found a new home in bluegrass. The famous Lloyd Loar Master Model from Gibson (1923) was designed to boost the flagging interest in mandolin ensembles, with little success. However, The "Loar" became the defining instrument of bluegrass music when Bill Monroe purchased F-5 S/N 73987 in a Florida barbershop in 1943 and popularized it as his main instrument.


The mandolin orchestras never completely went away, however. In fact, along with all the other musical forms the mandolin is involved with, the mandolin ensemble (groups usually arranged like the string section of a modern symphony orchestra, with first mandolins, second mandolins, mandolas, mandocellos, mando-basses, and guitars, and sometimes supplemented by other instruments) continues to grow in popularity. Since the mid-nineties, several public-school mandolin-based guitar programs have blossomed around the country, including Fretworks Mandolin and Guitar Orchestra, the first of its kind. The national organization, Classical Mandolin Society of America, founded by Norman Levine, represents these groups. Prominent modern mandolinists and composers for mandolin in the classical music tradition include Samuel Firstman, Howard Fry, Rudy Cipolla, Dave Apollon, Neil Gladd, Evan Marshall, Marilynn Mair and Mark Davis (the Mair-Davis Duo), Brian Israel, David Evans, Emanuil Shynkman, Radim Zenkl, David Del Tredici and Ernst Krenek.


When Cowan Powers and his family recorded their old-time music from 1924-1926, his daughter Orpha Powers was one of the earliest known southern-music artists to record with the mandolin. By the 1930s, single mandolins were becoming more commonly used in southern string band music, most notably by brother duets such as the sedate Blue Sky Boys (Bill Bolick and Earl Bolick) and the more hard-driving Monroe Brothers (Bill Monroe and Charlie Monroe). However, the mandolin's modern popularity in country music can be directly traced to one man: Bill Monroe, the father of bluegrass music. After the Monroe Brothers broke up in 1939, Bill Monroe formed his own group, after a brief time called the Blue Grass Boys, and completed the transition of mandolin styles from a "parlor" sound typical of brother duets to the modern "bluegrass" style. He joined the Grand Ole Opry in 1939 and its powerful clear-channel broadcast signal on WSM-AM spread his style throughout the South, directly inspiring many musicians to take up the mandolin. Monroe famously played Gibson F-5 mandolin, signed and dated July 9, 1923, by Lloyd Loar, chief acoustic engineer at Gibson. The F-5 has since become the most imitated tonally and aesthetically by modern builders.


Monroe's style involved playing lead melodies in the style of a fiddler, and also a percussive chording sound referred to as "the chop" for the sound made by the quickly struck and muted strings. He also perfected a sparse, percussive blues style, especially up the neck in keys that had not been used much in country music, notably B and E. He emphasized a powerful, syncopated right hand at the expense of left-hand virtuosity. Monroe's most influential follower of the second generation is Frank Wakefield and nowadays Mike Compton of the Nashville Bluegrass Band and David Long, who often tour as a duet. Tiny Moore of the Texas Playboys developed an electric five-string mandolin and helped popularize the instrument in Western Swing music.


Other major bluegrass mandolinists who emerged in the early 1950s and are still active include Jesse McReynolds (of Jim and Jesse) who invented a syncopated banjo-roll-like style called crosspicking—and Bobby Osborne of the Osborne Brothers, who is a master of clarity and sparkling single-note runs. Highly respected and influential modern bluegrass players include Herschel Sizemore, Doyle Lawson, and the multi-genre Sam Bush, who is equally at home with old-time fiddle tunes, rock, reggae, and jazz. Ronnie McCoury of the Del McCoury Band has won numerous awards for his Monroe-influenced playing. The late John Duffey of the original Country Gentlemen and later the Seldom Scene did much to popularize the bluegrass mandolin among folk and urban audiences, especially on the east coast and in the Washington, D.C. area.


Jethro Burns, best known as half of the comedy duo Homer and Jethro, was also the first important jazz mandolinist. Tiny Moore popularized the mandolin in Western swing music. He initially played an 8-string Gibson but switched after 1952 to a 5-string solidbody electric instrument built by Paul Bigsby. Modern players David Grisman, Sam Bush, and Mike Marshall, among others, have worked since the early 1970s to demonstrate the mandolin's versatility for all styles of music. Chris Thile of California is a well-known player, and has accomplished many feats of traditional bluegrass, classical, contemporary pop and rock; the band Nickel Creek featured his playing in its blend of traditional and pop styles, and he now plays in his band Punch Brothers. Most commonly associated with bluegrass, mandolin has been used a lot in country music over the years. Some well-known players include Marty Stuart, Vince Gill, and Ricky Skaggs.


Mandolin has also been used in blues music, most notably by Ry Cooder, who performed outstanding covers on his very first recordings, Yank Rachell, Johnny "Man" Young, Carl Martin, and Gerry Hundt. Howard Armstrong, who is famous for blues violin, got his start with his father's mandolin and played in string bands similar to the other Tennessee string bands he came into contact with, with band makeup including "mandolins and fiddles and guitars and banjos. And once in a while they would ease a little ukulele in there and a bass fiddle." Other blues players from the era's string bands include Willie Black (Whistler And His Jug Band), Dink Brister, Jim Hill, Charles Johnson, Coley Jones (Dallas String Band), Bobby Leecan (Need More Band), Alfred Martin, Charlie McCoy (1909-1950), Al Miller, Matthew Prater, and Herb Quinn.


The mandolin has been used occasionally in rock music, first appearing in the psychedelic era of the late 1960s. Levon Helm of The Band occasionally moved from his drum kit to play mandolin, most notably on Rag Mama Rag, Rockin' Chair, and Evangeline. Ian Anderson of Jethro Tull played mandolin on Fat Man, from their second album, Stand Up, and also occasionally on later releases. Rod Stewart's 1971 No. 1 hit Maggie May features a significant mandolin riff. David Grisman played mandolin on two Grateful Dead songs on the American Beauty album, Friend of the Devil and Ripple, which became instant favorites among amateur pickers at jam sessions and campground gatherings. John Paul Jones and Jimmy Page both played mandolin on Led Zeppelin songs. The popular alt rock group Imagine Dragons feature the mandolin on a few of their songs, most prominently being It's Time. Dash Crofts of the soft rock duo Seals and Crofts extensively used mandolin in their repertoire during the 1970s. Styx released the song Boat on the River in 1980, which featured Tommy Shaw on vocals and mandolin. The song didn't chart in the United States but was popular in much of Europe and the Philippines.


Some rock musicians today use mandolins, often single-stringed electric models rather than double-stringed acoustic mandolins. One example is Tim Brennan of the Irish-American punk rock band Dropkick Murphys. In addition to electric guitar, bass, and drums, the band uses several instruments associated with traditional Celtic music, including mandolin, tin whistle, and Great Highland bagpipes. The band explains that these instruments accentuate the growling sound they favor. The 1991 R.E.M. hit "Losing My Religion" was driven by a few simple mandolin licks played by guitarist Peter Buck, who also played the mandolin in nearly a dozen other songs. The single peaked at No. 4 on the Billboard Hot 100 chart (#1 on the rock and alternative charts), Luther Dickinson of North Mississippi Allstars and The Black Crowes has made frequent use of the mandolin, most notably on the Black Crowes song "Locust Street." Armenian American rock group System of A Down makes extensive use of the mandolin on their 2005 double album Mezmerize/Hypnotize. Pop punk band Green Day has used a mandolin in several occasions, especially on their 2000 album, Warning. Boyd Tinsley, violin player of the Dave Matthews Band has been using an electric mandolin since 2005. Frontman Colin Meloy and guitarist Chris Funk of The Decemberists regularly employ the mandolin in the band's music. Nancy Wilson, rhythm guitarist of Heart, uses a mandolin in Heart's song "Dream of the Archer" from the album Little Queen, as well as in Heart's cover of Led Zeppelin's song "The Battle of Evermore." "Show Me Heaven" by Maria McKee, the theme song to the film Days of Thunder, prominently features a mandolin.


As in Brazil, the mandolin has played an important role in the Music of Venezuela. It has enjoyed a privileged position as the main melodic instrument in several different regions of the country. Specifically, the eastern states of Sucre, Nueva Esparta, Anzoategui and Monagas have made the mandolin the main instrument in their versions of Joropo as well as Puntos, Jotas, Polos, Fulias, Merengues and Malagueñas. Also, in the west of the country the sound of the mandolin is intrinsically associated with the regional genres of the Venezuelan Andes: Bambucos, Pasillos, Pasodobles, and Waltzes. In the western city of Maracaibo the Mandolin has been played in Decimas, Danzas and Contradanzas Zulianas; in the capital, Caracas, the Merengue Rucaneao, Pasodobles and Waltzes have also been played with mandolin for almost a century. Today, Venezuelan mandolists include an important group of virtuoso players and ensembles such as Alberto Valderrama, Jesus Rengel, Ricardo Sandoval, Saul Vera, and Cristobal Soto.


To fill this gap in the literature, mandolin orchestras have traditionally played many arrangements of music written for regular orchestras or other ensembles. Some players have sought out contemporary composers to solicit new works. Traditional mandolin orchestras remain especially popular in Japan and Germany, but also exist throughout the United States, Europe and the rest of the world. They perform works composed for mandolin family instruments, or re-orchestrations of traditional pieces. The structure of a contemporary traditional mandolin orchestra consists of: first and second mandolins, mandolas (either octave mandolas, tuned an octave below the mandolin, or tenor mandolas, tuned like the viola), mandocellos (tuned like the cello), and bass instruments (conventional string bass or, rarely, mandobasses). Smaller ensembles, such as quartets composed of two mandolins, mandola, and mandocello, may also be found.


Insects (from Latin insectum, a calque of Greek ἔντομον [éntomon], "cut into sections") are a class of invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. They are the most diverse group of animals on the planet, including more than a million described species and representing more than half of all known living organisms. The number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing animal life forms on Earth. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, a habitat dominated by another arthropod group, crustaceans.


The life cycles of insects vary but most hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages can differ from the adults in structure, habit and habitat, and can include a passive pupal stage in those groups that undergo 4-stage metamorphosis (see holometabolism). Insects that undergo 3-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The higher level relationship of the Hexapoda is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22–28 in). The most diverse insect groups appear to have coevolved with flowering plants.


Adult insects typically move about by walking, flying, or sometimes swimming (see below, Locomotion). As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles. Insects are the only invertebrates to have evolved flight. Many insects spend at least part of their lives under water, with larval adaptations that include gills, and some adult insects are aquatic and have adaptations for swimming. Some species, such as water striders, are capable of walking on the surface of water. Insects are mostly solitary, but some, such as certain bees, ants and termites, are social and live in large, well-organized colonies. Some insects, such as earwigs, show maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyridae in the beetle order Coleoptera communicate with light.


Humans regard certain insects as pests, and attempt to control them using insecticides and a host of other techniques. Some insects damage crops by feeding on sap, leaves or fruits. A few parasitic species are pathogenic. Some insects perform complex ecological roles; blow-flies, for example, help consume carrion but also spread diseases. Insect pollinators are essential to the life-cycle of many flowering plant species on which most organisms, including humans, are at least partly dependent; without them, the terrestrial portion of the biosphere (including humans) would be devastated. Many other insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms and bees have been used extensively by humans for the production of silk and honey, respectively. In some cultures, people eat the larvae or adults of certain insects.


The word "insect" comes from the Latin word insectum, meaning "with a notched or divided body", or literally "cut into", from the neuter singular perfect passive participle of insectare, "to cut into, to cut up", from in- "into" and secare "to cut"; because insects appear "cut into" three sections. Pliny the Elder introduced the Latin designation as a loan-translation of the Greek word ἔντομος (éntomos) or "insect" (as in entomology), which was Aristotle's term for this class of life, also in reference to their "notched" bodies. "Insect" first appears documented in English in 1601 in Holland's translation of Pliny. Translations of Aristotle's term also form the usual word for "insect" in Welsh (trychfil, from trychu "to cut" and mil, "animal"), Serbo-Croatian (zareznik, from rezati, "to cut"), Russian (насекомое nasekomoje, from seč'/-sekat', "to cut"), etc.


The higher-level phylogeny of the arthropods continues to be a matter of debate and research. In 2008, researchers at Tufts University uncovered what they believe is the world's oldest known full-body impression of a primitive flying insect, a 300 million-year-old specimen from the Carboniferous period. The oldest definitive insect fossil is the Devonian Rhyniognatha hirsti, from the 396-million-year-old Rhynie chert. It may have superficially resembled a modern-day silverfish insect. This species already possessed dicondylic mandibles (two articulations in the mandible), a feature associated with winged insects, suggesting that wings may already have evolved at this time. Thus, the first insects probably appeared earlier, in the Silurian period.


Late Carboniferous and Early Permian insect orders include both extant groups, their stem groups, and a number of Paleozoic groups, now extinct. During this era, some giant dragonfly-like forms reached wingspans of 55 to 70 cm (22 to 28 in), making them far larger than any living insect. This gigantism may have been due to higher atmospheric oxygen levels that allowed increased respiratory efficiency relative to today. The lack of flying vertebrates could have been another factor. Most extinct orders of insects developed during the Permian period that began around 270 million years ago. Many of the early groups became extinct during the Permian-Triassic extinction event, the largest mass extinction in the history of the Earth, around 252 million years ago.


Insects were among the earliest terrestrial herbivores and acted as major selection agents on plants. Plants evolved chemical defenses against this herbivory and the insects, in turn, evolved mechanisms to deal with plant toxins. Many insects make use of these toxins to protect themselves from their predators. Such insects often advertise their toxicity using warning colors. This successful evolutionary pattern has also been used by mimics. Over time, this has led to complex groups of coevolved species. Conversely, some interactions between plants and insects, like pollination, are beneficial to both organisms. Coevolution has led to the development of very specific mutualisms in such systems.


Insects can be divided into two groups historically treated as subclasses: wingless insects, known as Apterygota, and winged insects, known as Pterygota. The Apterygota consist of the primitively wingless order of the silverfish (Thysanura). Archaeognatha make up the Monocondylia based on the shape of their mandibles, while Thysanura and Pterygota are grouped together as Dicondylia. The Thysanura themselves possibly are not monophyletic, with the family Lepidotrichidae being a sister group to the Dicondylia (Pterygota and the remaining Thysanura).


Traditional morphology-based or appearance-based systematics have usually given the Hexapoda the rank of superclass,:180 and identified four groups within it: insects (Ectognatha), springtails (Collembola), Protura, and Diplura, the latter three being grouped together as the Entognatha on the basis of internalized mouth parts. Supraordinal relationships have undergone numerous changes with the advent of methods based on evolutionary history and genetic data. A recent theory is that the Hexapoda are polyphyletic (where the last common ancestor was not a member of the group), with the entognath classes having separate evolutionary histories from the Insecta. Many of the traditional appearance-based taxa have been shown to be paraphyletic, so rather than using ranks like subclass, superorder, and infraorder, it has proved better to use monophyletic groupings (in which the last common ancestor is a member of the group). The following represents the best-supported monophyletic groupings for the Insecta.


Paleoptera and Neoptera are the winged orders of insects differentiated by the presence of hardened body parts called sclerites, and in the Neoptera, muscles that allow their wings to fold flatly over the abdomen. Neoptera can further be divided into incomplete metamorphosis-based (Polyneoptera and Paraneoptera) and complete metamorphosis-based groups. It has proved difficult to clarify the relationships between the orders in Polyneoptera because of constant new findings calling for revision of the taxa. For example, the Paraneoptera have turned out to be more closely related to the Endopterygota than to the rest of the Exopterygota. The recent molecular finding that the traditional louse orders Mallophaga and Anoplura are derived from within Psocoptera has led to the new taxon Psocodea. Phasmatodea and Embiidina have been suggested to form the Eukinolabia. Mantodea, Blattodea, and Isoptera are thought to form a monophyletic group termed Dictyoptera.


The Exopterygota likely are paraphyletic in regard to the Endopterygota. Matters that have incurred controversy include Strepsiptera and Diptera grouped together as Halteria based on a reduction of one of the wing pairs – a position not well-supported in the entomological community. The Neuropterida are often lumped or split on the whims of the taxonomist. Fleas are now thought to be closely related to boreid mecopterans. Many questions remain in the basal relationships amongst endopterygote orders, particularly the Hymenoptera.


Though the true dimensions of species diversity remain uncertain, estimates range from 2.6–7.8 million species with a mean of 5.5 million. This probably represents less than 20% of all species on Earth[citation needed], and with only about 20,000 new species of all organisms being described each year, most species likely will remain undescribed for many years unless species descriptions increase in rate. About 850,000–1,000,000 of all described species are insects. Of the 24 orders of insects, four dominate in terms of numbers of described species, with at least 3 million species included in Coleoptera, Diptera, Hymenoptera and Lepidoptera. A recent study estimated the number of beetles at 0.9–2.1 million with a mean of 1.5 million.


Insects have segmented bodies supported by exoskeletons, the hard outer covering made mostly of chitin. The segments of the body are organized into three distinctive but interconnected units, or tagmata: a head, a thorax and an abdomen. The head supports a pair of sensory antennae, a pair of compound eyes, and, if present, one to three simple eyes (or ocelli) and three sets of variously modified appendages that form the mouthparts. The thorax has six segmented legs—one pair each for the prothorax, mesothorax and the metathorax segments making up the thorax—and, none, two or four wings. The abdomen consists of eleven segments, though in a few species of insects, these segments may be fused together or reduced in size. The abdomen also contains most of the digestive, respiratory, excretory and reproductive internal structures.:22–48 Considerable variation and many adaptations in the body parts of insects occur, especially wings, legs, antenna and mouthparts.


The head is enclosed in a hard, heavily sclerotized, unsegmented, exoskeletal head capsule, or epicranium, which contains most of the sensing organs, including the antennae, ocellus or eyes, and the mouthparts. Of all the insect orders, Orthoptera displays the most features found in other insects, including the sutures and sclerites. Here, the vertex, or the apex (dorsal region), is situated between the compound eyes for insects with a hypognathous and opisthognathous head. In prognathous insects, the vertex is not found between the compound eyes, but rather, where the ocelli are normally. This is because the primary axis of the head is rotated 90° to become parallel to the primary axis of the body. In some species, this region is modified and assumes a different name.:13


The thorax is a tagma composed of three sections, the prothorax, mesothorax and the metathorax. The anterior segment, closest to the head, is the prothorax, with the major features being the first pair of legs and the pronotum. The middle segment is the mesothorax, with the major features being the second pair of legs and the anterior wings. The third and most posterior segment, abutting the abdomen, is the metathorax, which features the third pair of legs and the posterior wings. Each segment is dilineated by an intersegmental suture. Each segment has four basic regions. The dorsal surface is called the tergum (or notum) to distinguish it from the abdominal terga. The two lateral regions are called the pleura (singular: pleuron) and the ventral aspect is called the sternum. In turn, the notum of the prothorax is called the pronotum, the notum for the mesothorax is called the mesonotum and the notum for the metathorax is called the metanotum. Continuing with this logic, the mesopleura and metapleura, as well as the mesosternum and metasternum, are used.


The abdomen is the largest tagma of the insect, which typically consists of 11–12 segments and is less strongly sclerotized than the head or thorax. Each segment of the abdomen is represented by a sclerotized tergum and sternum. Terga are separated from each other and from the adjacent sterna or pleura by membranes. Spiracles are located in the pleural area. Variation of this ground plan includes the fusion of terga or terga and sterna to form continuous dorsal or ventral shields or a conical tube. Some insects bear a sclerite in the pleural area called a laterotergite. Ventral sclerites are sometimes called laterosternites. During the embryonic stage of many insects and the postembryonic stage of primitive insects, 11 abdominal segments are present. In modern insects there is a tendency toward reduction in the number of the abdominal segments, but the primitive number of 11 is maintained during embryogenesis. Variation in abdominal segment number is considerable. If the Apterygota are considered to be indicative of the ground plan for pterygotes, confusion reigns: adult Protura have 12 segments, Collembola have 6. The orthopteran family Acrididae has 11 segments, and a fossil specimen of Zoraptera has a 10-segmented abdomen.


The insect outer skeleton, the cuticle, is made up of two layers: the epicuticle, which is a thin and waxy water resistant outer layer and contains no chitin, and a lower layer called the procuticle. The procuticle is chitinous and much thicker than the epicuticle and has two layers: an outer layer known as the exocuticle and an inner layer known as the endocuticle. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each other in a sandwich pattern, while the exocuticle is rigid and hardened.:22–24 The exocuticle is greatly reduced in many soft-bodied insects (e.g., caterpillars), especially during their larval stages.


Insects are the only invertebrates to have developed active flight capability, and this has played an important role in their success.:186 Their muscles are able to contract multiple times for each single nerve impulse, allowing the wings to beat faster than would ordinarily be possible. Having their muscles attached to their exoskeletons is more efficient and allows more muscle connections; crustaceans also use the same method, though all spiders use hydraulic pressure to extend their legs, a system inherited from their pre-arthropod ancestors. Unlike insects, though, most aquatic crustaceans are biomineralized with calcium carbonate extracted from the water.


The thoracic segments have one ganglion on each side, which are connected into a pair, one pair per segment. This arrangement is also seen in the abdomen but only in the first eight segments. Many species of insects have reduced numbers of ganglia due to fusion or reduction. Some cockroaches have just six ganglia in the abdomen, whereas the wasp Vespa crabro has only two in the thorax and three in the abdomen. Some insects, like the house fly Musca domestica, have all the body ganglia fused into a single large thoracic ganglion.


At least a few insects have nociceptors, cells that detect and transmit sensations of pain. This was discovered in 2003 by studying the variation in reactions of larvae of the common fruitfly Drosophila to the touch of a heated probe and an unheated one. The larvae reacted to the touch of the heated probe with a stereotypical rolling behavior that was not exhibited when the larvae were touched by the unheated probe. Although nociception has been demonstrated in insects, there is no consensus that insects feel pain consciously


The salivary glands (element 30 in numbered diagram) in an insect's mouth produce saliva. The salivary ducts lead from the glands to the reservoirs and then forward through the head to an opening called the salivarium, located behind the hypopharynx. By moving its mouthparts (element 32 in numbered diagram) the insect can mix its food with saliva. The mixture of saliva and food then travels through the salivary tubes into the mouth, where it begins to break down. Some insects, like flies, have extra-oral digestion. Insects using extra-oral digestion expel digestive enzymes onto their food to break it down. This strategy allows insects to extract a significant proportion of the available nutrients from the food source.:31 The gut is where almost all of insects' digestion takes place. It can be divided into the foregut, midgut and hindgut.


Once food leaves the crop, it passes to the midgut (element 13 in numbered diagram), also known as the mesenteron, where the majority of digestion takes place. Microscopic projections from the midgut wall, called microvilli, increase the surface area of the wall and allow more nutrients to be absorbed; they tend to be close to the origin of the midgut. In some insects, the role of the microvilli and where they are located may vary. For example, specialized microvilli producing digestive enzymes may more likely be near the end of the midgut, and absorption near the origin or beginning of the midgut.:32


In the hindgut (element 16 in numbered diagram), or proctodaeum, undigested food particles are joined by uric acid to form fecal pellets. The rectum absorbs 90% of the water in these fecal pellets, and the dry pellet is then eliminated through the anus (element 17), completing the process of digestion. The uric acid is formed using hemolymph waste products diffused from the Malpighian tubules (element 20). It is then emptied directly into the alimentary canal, at the junction between the midgut and hindgut. The number of Malpighian tubules possessed by a given insect varies between species, ranging from only two tubules in some insects to over 100 tubules in others.:71–72, 78–80


The reproductive system of female insects consist of a pair of ovaries, accessory glands, one or more spermathecae, and ducts connecting these parts. The ovaries are made up of a number of egg tubes, called ovarioles, which vary in size and number by species. The number of eggs that the insect is able to make vary by the number of ovarioles with the rate that eggs can be develop being also influenced by ovariole design. Female insects are able make eggs, receive and store sperm, manipulate sperm from different males, and lay eggs. Accessory glands or glandular parts of the oviducts produce a variety of substances for sperm maintenance, transport and fertilization, as well as for protection of eggs. They can produce glue and protective substances for coating eggs or tough coverings for a batch of eggs called oothecae. Spermathecae are tubes or sacs in which sperm can be stored between the time of mating and the time an egg is fertilized.:880


For males, the reproductive system is the testis, suspended in the body cavity by tracheae and the fat body. Most male insects have a pair of testes, inside of which are sperm tubes or follicles that are enclosed within a membranous sac. The follicles connect to the vas deferens by the vas efferens, and the two tubular vasa deferentia connect to a median ejaculatory duct that leads to the outside. A portion of the vas deferens is often enlarged to form the seminal vesicle, which stores the sperm before they are discharged into the female. The seminal vesicles have glandular linings that secrete nutrients for nourishment and maintenance of the sperm. The ejaculatory duct is derived from an invagination of the epidermal cells during development and, as a result, has a cuticular lining. The terminal portion of the ejaculatory duct may be sclerotized to form the intromittent organ, the aedeagus. The remainder of the male reproductive system is derived from embryonic mesoderm, except for the germ cells, or spermatogonia, which descend from the primordial pole cells very early during embryogenesis.:885


Insect respiration is accomplished without lungs. Instead, the insect respiratory system uses a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their trachea (element 8 in numbered diagram). Since oxygen is delivered directly, the circulatory system is not used to carry oxygen, and is therefore greatly reduced. The insect circulatory system has no veins or arteries, and instead consists of little more than a single, perforated dorsal tube which pulses peristaltically. Toward the thorax, the dorsal tube (element 14) divides into chambers and acts like the insect's heart. The opposite end of the dorsal tube is like the aorta of the insect circulating the hemolymph, arthropods' fluid analog of blood, inside the body cavity.:61–65 Air is taken in through openings on the sides of the abdomen called spiracles.


There are many different patterns of gas exchange demonstrated by different groups of insects. Gas exchange patterns in insects can range from continuous and diffusive ventilation, to discontinuous gas exchange.:65–68 During continuous gas exchange, oxygen is taken in and carbon dioxide is released in a continuous cycle. In discontinuous gas exchange, however, the insect takes in oxygen while it is active and small amounts of carbon dioxide are released when the insect is at rest. Diffusive ventilation is simply a form of continuous gas exchange that occurs by diffusion rather than physically taking in the oxygen. Some species of insect that are submerged also have adaptations to aid in respiration. As larvae, many insects have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies which may be held or trapped in special structures.


The majority of insects hatch from eggs. The fertilization and development takes place inside the egg, enclosed by a shell (chorion) that consists of maternal tissue. In contrast to eggs of other arthropods, most insect eggs are drought resistant. This is because inside the chorion two additional membranes develop from embryonic tissue, the amnion and the serosa. This serosa secretes a cuticle rich in chitin that protects the embryo against desiccation. In Schizophora however the serosa does not develop, but these flies lay their eggs in damp places, such as rotting matter. Some species of insects, like the cockroach Blaptica dubia, as well as juvenile aphids and tsetse flies, are ovoviviparous. The eggs of ovoviviparous animals develop entirely inside the female, and then hatch immediately upon being laid. Some other species, such as those in the genus of cockroaches known as Diploptera, are viviparous, and thus gestate inside the mother and are born alive.:129, 131, 134–135 Some insects, like parasitic wasps, show polyembryony, where a single fertilized egg divides into many and in some cases thousands of separate embryos.:136–137 Insects may be univoltine, bivoltine or multivoltine, i.e. they may have one, two or many broods (generations) in a year.


Other developmental and reproductive variations include haplodiploidy, polymorphism, paedomorphosis or peramorphosis, sexual dimorphism, parthenogenesis and more rarely hermaphroditism.:143 In haplodiploidy, which is a type of sex-determination system, the offspring's sex is determined by the number of sets of chromosomes an individual receives. This system is typical in bees and wasps. Polymorphism is where a species may have different morphs or forms, as in the oblong winged katydid, which has four different varieties: green, pink and yellow or tan. Some insects may retain phenotypes that are normally only seen in juveniles; this is called paedomorphosis. In peramorphosis, an opposite sort of phenomenon, insects take on previously unseen traits after they have matured into adults. Many insects display sexual dimorphism, in which males and females have notably different appearances, such as the moth Orgyia recens as an exemplar of sexual dimorphism in insects.


Some insects use parthenogenesis, a process in which the female can reproduce and give birth without having the eggs fertilized by a male. Many aphids undergo a form of parthenogenesis, called cyclical parthenogenesis, in which they alternate between one or many generations of asexual and sexual reproduction. In summer, aphids are generally female and parthenogenetic; in the autumn, males may be produced for sexual reproduction. Other insects produced by parthenogenesis are bees, wasps and ants, in which they spawn males. However, overall, most individuals are female, which are produced by fertilization. The males are haploid and the females are diploid. More rarely, some insects display hermaphroditism, in which a given individual has both male and female reproductive organs.


Hemimetabolous insects, those with incomplete metamorphosis, change gradually by undergoing a series of molts. An insect molts when it outgrows its exoskeleton, which does not stretch and would otherwise restrict the insect's growth. The molting process begins as the insect's epidermis secretes a new epicuticle inside the old one. After this new epicuticle is secreted, the epidermis releases a mixture of enzymes that digests the endocuticle and thus detaches the old cuticle. When this stage is complete, the insect makes its body swell by taking in a large quantity of water or air, which makes the old cuticle split along predefined weaknesses where the old exocuticle was thinnest.:142


Holometabolism, or complete metamorphosis, is where the insect changes in four stages, an egg or embryo, a larva, a pupa and the adult or imago. In these species, an egg hatches to produce a larva, which is generally worm-like in form. This worm-like form can be one of several varieties: eruciform (caterpillar-like), scarabaeiform (grub-like), campodeiform (elongated, flattened and active), elateriform (wireworm-like) or vermiform (maggot-like). The larva grows and eventually becomes a pupa, a stage marked by reduced movement and often sealed within a cocoon. There are three types of pupae: obtect, exarate or coarctate. Obtect pupae are compact, with the legs and other appendages enclosed. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin.:151 Insects undergo considerable change in form during the pupal stage, and emerge as adults. Butterflies are a well-known example of insects that undergo complete metamorphosis, although most insects use this life cycle. Some insects have evolved this system to hypermetamorphosis.


Many insects possess very sensitive and, or specialized organs of perception. Some insects such as bees can perceive ultraviolet wavelengths, or detect polarized light, while the antennae of male moths can detect the pheromones of female moths over distances of many kilometers. The yellow paper wasp (Polistes versicolor) is known for its wagging movements as a form of communication within the colony; it can waggle with a frequency of 10.6±2.1 Hz (n=190). These wagging movements can signal the arrival of new material into the nest and aggression between workers can be used to stimulate others to increase foraging expeditions. There is a pronounced tendency for there to be a trade-off between visual acuity and chemical or tactile acuity, such that most insects with well-developed eyes have reduced or simple antennae, and vice versa. There are a variety of different mechanisms by which insects perceive sound, while the patterns are not universal, insects can generally hear sound if they can produce it. Different insect species can have varying hearing, though most insects can hear only a narrow range of frequencies related to the frequency of the sounds they can produce. Mosquitoes have been found to hear up to 2 kHz., and some grasshoppers can hear up to 50 kHz. Certain predatory and parasitic insects can detect the characteristic sounds made by their prey or hosts, respectively. For instance, some nocturnal moths can perceive the ultrasonic emissions of bats, which helps them avoid predation.:87–94 Insects that feed on blood have special sensory structures that can detect infrared emissions, and use them to home in on their hosts.


Some insects display a rudimentary sense of numbers, such as the solitary wasps that prey upon a single species. The mother wasp lays her eggs in individual cells and provides each egg with a number of live caterpillars on which the young feed when hatched. Some species of wasp always provide five, others twelve, and others as high as twenty-four caterpillars per cell. The number of caterpillars is different among species, but always the same for each sex of larva. The male solitary wasp in the genus Eumenes is smaller than the female, so the mother of one species supplies him with only five caterpillars; the larger female receives ten caterpillars in her cell.


A few insects, such as members of the families Poduridae and Onychiuridae (Collembola), Mycetophilidae (Diptera) and the beetle families Lampyridae, Phengodidae, Elateridae and Staphylinidae are bioluminescent. The most familiar group are the fireflies, beetles of the family Lampyridae. Some species are able to control this light generation to produce flashes. The function varies with some species using them to attract mates, while others use them to lure prey. Cave dwelling larvae of Arachnocampa (Mycetophilidae, Fungus gnats) glow to lure small flying insects into sticky strands of silk. Some fireflies of the genus Photuris mimic the flashing of female Photinus species to attract males of that species, which are then captured and devoured. The colors of emitted light vary from dull blue (Orfelia fultoni, Mycetophilidae) to the familiar greens and the rare reds (Phrixothrix tiemanni, Phengodidae).


Most insects, except some species of cave crickets, are able to perceive light and dark. Many species have acute vision capable of detecting minute movements. The eyes may include simple eyes or ocelli as well as compound eyes of varying sizes. Many species are able to detect light in the infrared, ultraviolet and the visible light wavelengths. Color vision has been demonstrated in many species and phylogenetic analysis suggests that UV-green-blue trichromacy existed from at least the Devonian period between 416 and 359 million years ago.


Insects were the earliest organisms to produce and sense sounds. Insects make sounds mostly by mechanical action of appendages. In grasshoppers and crickets, this is achieved by stridulation. Cicadas make the loudest sounds among the insects by producing and amplifying sounds with special modifications to their body and musculature. The African cicada Brevisana brevis has been measured at 106.7 decibels at a distance of 50 cm (20 in). Some insects, such as the Helicoverpa zeamoths, hawk moths and Hedylid butterflies, can hear ultrasound and take evasive action when they sense that they have been detected by bats. Some moths produce ultrasonic clicks that were once thought to have a role in jamming bat echolocation. The ultrasonic clicks were subsequently found to be produced mostly by unpalatable moths to warn bats, just as warning colorations are used against predators that hunt by sight. Some otherwise palatable moths have evolved to mimic these calls. More recently, the claim that some moths can jam bat sonar has been revisited. Ultrasonic recording and high-speed infrared videography of bat-moth interactions suggest the palatable tiger moth really does defend against attacking big brown bats using ultrasonic clicks that jam bat sonar.


Very low sounds are also produced in various species of Coleoptera, Hymenoptera, Lepidoptera, Mantodea and Neuroptera. These low sounds are simply the sounds made by the insect's movement. Through microscopic stridulatory structures located on the insect's muscles and joints, the normal sounds of the insect moving are amplified and can be used to warn or communicate with other insects. Most sound-making insects also have tympanal organs that can perceive airborne sounds. Some species in Hemiptera, such as the corixids (water boatmen), are known to communicate via underwater sounds. Most insects are also able to sense vibrations transmitted through surfaces.


Some species use vibrations for communicating within members of the same species, such as to attract mates as in the songs of the shield bug Nezara viridula. Vibrations can also be used to communicate between entirely different species; lycaenid (gossamer-winged butterfly) caterpillars which are myrmecophilous (living in a mutualistic association with ants) communicate with ants in this way. The Madagascar hissing cockroach has the ability to press air through its spiracles to make a hissing noise as a sign of aggression; the Death's-head Hawkmoth makes a squeaking noise by forcing air out of their pharynx when agitated, which may also reduce aggressive worker honey bee behavior when the two are in close proximity.


Chemical communications in animals rely on a variety of aspects including taste and smell. Chemoreception is the physiological response of a sense organ (i.e. taste or smell) to a chemical stimulus where the chemicals act as signals to regulate the state or activity of a cell. A semiochemical is a message-carrying chemical that is meant to attract, repel, and convey information. Types of semiochemicals include pheromones and kairomones. One example is the butterfly Phengaris arion which uses chemical signals as a form of mimicry to aid in predation.


In addition to the use of sound for communication, a wide range of insects have evolved chemical means for communication. These chemicals, termed semiochemicals, are often derived from plant metabolites include those meant to attract, repel and provide other kinds of information. Pheromones, a type of semiochemical, are used for attracting mates of the opposite sex, for aggregating conspecific individuals of both sexes, for deterring other individuals from approaching, to mark a trail, and to trigger aggression in nearby individuals. Allomonea benefit their producer by the effect they have upon the receiver. Kairomones benefit their receiver instead of their producer. Synomones benefit the producer and the receiver. While some chemicals are targeted at individuals of the same species, others are used for communication across species. The use of scents is especially well known to have developed in social insects.:96–105


Social insects, such as termites, ants and many bees and wasps, are the most familiar species of eusocial animal. They live together in large well-organized colonies that may be so tightly integrated and genetically similar that the colonies of some species are sometimes considered superorganisms. It is sometimes argued that the various species of honey bee are the only invertebrates (and indeed one of the few non-human groups) to have evolved a system of abstract symbolic communication where a behavior is used to represent and convey specific information about something in the environment. In this communication system, called dance language, the angle at which a bee dances represents a direction relative to the sun, and the length of the dance represents the distance to be flown.:309–311 Though perhaps not as advanced as honey bees, bumblebees also potentially have some social communication behaviors. Bombus terrestris, for example, exhibit a faster learning curve for visiting unfamiliar, yet rewarding flowers, when they can see a conspecific foraging on the same species.


Only insects which live in nests or colonies demonstrate any true capacity for fine-scale spatial orientation or homing. This can allow an insect to return unerringly to a single hole a few millimeters in diameter among thousands of apparently identical holes clustered together, after a trip of up to several kilometers' distance. In a phenomenon known as philopatry, insects that hibernate have shown the ability to recall a specific location up to a year after last viewing the area of interest. A few insects seasonally migrate large distances between different geographic regions (e.g., the overwintering areas of the Monarch butterfly).:14


The eusocial insects build nest, guard eggs, and provide food for offspring full-time (see Eusociality). Most insects, however, lead short lives as adults, and rarely interact with one another except to mate or compete for mates. A small number exhibit some form of parental care, where they will at least guard their eggs, and sometimes continue guarding their offspring until adulthood, and possibly even feeding them. Another simple form of parental care is to construct a nest (a burrow or an actual construction, either of which may be simple or complex), store provisions in it, and lay an egg upon those provisions. The adult does not contact the growing offspring, but it nonetheless does provide food. This sort of care is typical for most species of bees and various types of wasps.


Insects are the only group of invertebrates to have developed flight. The evolution of insect wings has been a subject of debate. Some entomologists suggest that the wings are from paranotal lobes, or extensions from the insect's exoskeleton called the nota, called the paranotal theory. Other theories are based on a pleural origin. These theories include suggestions that wings originated from modified gills, spiracular flaps or as from an appendage of the epicoxa. The epicoxal theory suggests the insect wings are modified epicoxal exites, a modified appendage at the base of the legs or coxa. In the Carboniferous age, some of the Meganeura dragonflies had as much as a 50 cm (20 in) wide wingspan. The appearance of gigantic insects has been found to be consistent with high atmospheric oxygen. The respiratory system of insects constrains their size, however the high oxygen in the atmosphere allowed larger sizes. The largest flying insects today are much smaller and include several moth species such as the Atlas moth and the White Witch (Thysania agrippina).


Many adult insects use six legs for walking and have adopted a tripedal gait. The tripedal gait allows for rapid walking while always having a stable stance and has been studied extensively in cockroaches. The legs are used in alternate triangles touching the ground. For the first step, the middle right leg and the front and rear left legs are in contact with the ground and move the insect forward, while the front and rear right leg and the middle left leg are lifted and moved forward to a new position. When they touch the ground to form a new stable triangle the other legs can be lifted and brought forward in turn and so on. The purest form of the tripedal gait is seen in insects moving at high speeds. However, this type of locomotion is not rigid and insects can adapt a variety of gaits. For example, when moving slowly, turning, or avoiding obstacles, four or more feet may be touching the ground. Insects can also adapt their gait to cope with the loss of one or more limbs.


Cockroaches are among the fastest insect runners and, at full speed, adopt a bipedal run to reach a high velocity in proportion to their body size. As cockroaches move very quickly, they need to be video recorded at several hundred frames per second to reveal their gait. More sedate locomotion is seen in the stick insects or walking sticks (Phasmatodea). A few insects have evolved to walk on the surface of the water, especially members of the Gerridae family, commonly known as water striders. A few species of ocean-skaters in the genus Halobates even live on the surface of open oceans, a habitat that has few insect species.


Many of these species have adaptations to help in under-water locomotion. Water beetles and water bugs have legs adapted into paddle-like structures. Dragonfly naiads use jet propulsion, forcibly expelling water out of their rectal chamber. Some species like the water striders are capable of walking on the surface of water. They can do this because their claws are not at the tips of the legs as in most insects, but recessed in a special groove further up the leg; this prevents the claws from piercing the water's surface film. Other insects such as the Rove beetle Stenus are known to emit pygidial gland secretions that reduce surface tension making it possible for them to move on the surface of water by Marangoni propulsion (also known by the German term Entspannungsschwimmen).


Insect ecology is the scientific study of how insects, individually or as a community, interact with the surrounding environment or ecosystem.:3 Insects play one of the most important roles in their ecosystems, which includes many roles, such as soil turning and aeration, dung burial, pest control, pollination and wildlife nutrition. An example is the beetles, which are scavengers that feed on dead animals and fallen trees and thereby recycle biological materials into forms found useful by other organisms. These insects, and others, are responsible for much of the process by which topsoil is created.:3, 218–228


Camouflage is an important defense strategy, which involves the use of coloration or shape to blend into the surrounding environment. This sort of protective coloration is common and widespread among beetle families, especially those that feed on wood or vegetation, such as many of the leaf beetles (family Chrysomelidae) or weevils. In some of these species, sculpturing or various colored scales or hairs cause the beetle to resemble bird dung or other inedible objects. Many of those that live in sandy environments blend in with the coloration of the substrate. Most phasmids are known for effectively replicating the forms of sticks and leaves, and the bodies of some species (such as O. macklotti and Palophus centaurus) are covered in mossy or lichenous outgrowths that supplement their disguise. Some species have the ability to change color as their surroundings shift (B. scabrinota, T. californica). In a further behavioral adaptation to supplement crypsis, a number of species have been noted to perform a rocking motion where the body is swayed from side to side that is thought to reflect the movement of leaves or twigs swaying in the breeze. Another method by which stick insects avoid predation and resemble twigs is by feigning death (catalepsy), where the insect enters a motionless state that can be maintained for a long period. The nocturnal feeding habits of adults also aids Phasmatodea in remaining concealed from predators.


Another defense that often uses color or shape to deceive potential enemies is mimicry. A number of longhorn beetles (family Cerambycidae) bear a striking resemblance to wasps, which helps them avoid predation even though the beetles are in fact harmless. Batesian and Müllerian mimicry complexes are commonly found in Lepidoptera. Genetic polymorphism and natural selection give rise to otherwise edible species (the mimic) gaining a survival advantage by resembling inedible species (the model). Such a mimicry complex is referred to as Batesian and is most commonly known by the mimicry by the limenitidine Viceroy butterfly of the inedible danaine Monarch. Later research has discovered that the Viceroy is, in fact more toxic than the Monarch and this resemblance should be considered as a case of Müllerian mimicry. In Müllerian mimicry, inedible species, usually within a taxonomic order, find it advantageous to resemble each other so as to reduce the sampling rate by predators who need to learn about the insects' inedibility. Taxa from the toxic genus Heliconius form one of the most well known Müllerian complexes.


Chemical defense is another important defense found amongst species of Coleoptera and Lepidoptera, usually being advertised by bright colors, such as the Monarch butterfly. They obtain their toxicity by sequestering the chemicals from the plants they eat into their own tissues. Some Lepidoptera manufacture their own toxins. Predators that eat poisonous butterflies and moths may become sick and vomit violently, learning not to eat those types of species; this is actually the basis of Müllerian mimicry. A predator who has previously eaten a poisonous lepidopteran may avoid other species with similar markings in the future, thus saving many other species as well. Some ground beetles of the Carabidae family can spray chemicals from their abdomen with great accuracy, to repel predators.


Pollination is the process by which pollen is transferred in the reproduction of plants, thereby enabling fertilisation and sexual reproduction. Most flowering plants require an animal to do the transportation. While other animals are included as pollinators, the majority of pollination is done by insects. Because insects usually receive benefit for the pollination in the form of energy rich nectar it is a grand example of mutualism. The various flower traits (and combinations thereof) that differentially attract one type of pollinator or another are known as pollination syndromes. These arose through complex plant-animal adaptations. Pollinators find flowers through bright colorations, including ultraviolet, and attractant pheromones. The study of pollination by insects is known as anthecology.


Many insects are considered pests by humans. Insects commonly regarded as pests include those that are parasitic (e.g. lice, bed bugs), transmit diseases (mosquitoes, flies), damage structures (termites), or destroy agricultural goods (locusts, weevils). Many entomologists are involved in various forms of pest control, as in research for companies to produce insecticides, but increasingly rely on methods of biological pest control, or biocontrol. Biocontrol uses one organism to reduce the population density of another organism — the pest — and is considered a key element of integrated pest management.


Although pest insects attract the most attention, many insects are beneficial to the environment and to humans. Some insects, like wasps, bees, butterflies and ants, pollinate flowering plants. Pollination is a mutualistic relationship between plants and insects. As insects gather nectar from different plants of the same species, they also spread pollen from plants on which they have previously fed. This greatly increases plants' ability to cross-pollinate, which maintains and possibly even improves their evolutionary fitness. This ultimately affects humans since ensuring healthy crops is critical to agriculture. As well as pollination ants help with seed distribution of plants. This helps to spread the plants which increases plant diversity. This leads to an overall better environment. A serious environmental problem is the decline of populations of pollinator insects, and a number of species of insects are now cultured primarily for pollination management in order to have sufficient pollinators in the field, orchard or greenhouse at bloom time.:240–243 Another solution, as shown in Delaware, has been to raise native plants to help support native pollinators like L. vierecki. Insects also produce useful substances such as honey, wax, lacquer and silk. Honey bees have been cultured by humans for thousands of years for honey, although contracting for crop pollination is becoming more significant for beekeepers. The silkworm has greatly affected human history, as silk-driven trade established relationships between China and the rest of the world.


Insectivorous insects, or insects which feed on other insects, are beneficial to humans because they eat insects that could cause damage to agriculture and human structures. For example, aphids feed on crops and cause problems for farmers, but ladybugs feed on aphids, and can be used as a means to get significantly reduce pest aphid populations. While birds are perhaps more visible predators of insects, insects themselves account for the vast majority of insect consumption. Ants also help control animal populations by consuming small vertebrates. Without predators to keep them in check, insects can undergo almost unstoppable population explosions.:328–348:400


Insects play important roles in biological research. For example, because of its small size, short generation time and high fecundity, the common fruit fly Drosophila melanogaster is a model organism for studies in the genetics of higher eukaryotes. D. melanogaster has been an essential part of studies into principles like genetic linkage, interactions between genes, chromosomal genetics, development, behavior and evolution. Because genetic systems are well conserved among eukaryotes, understanding basic cellular processes like DNA replication or transcription in fruit flies can help to understand those processes in other eukaryotes, including humans. The genome of D. melanogaster was sequenced in 2000, reflecting the organism's important role in biological research. It was found that 70% of the fly genome is similar to the human genome, supporting the evolution theory.


In some cultures, insects, especially deep-fried cicadas, are considered to be delicacies, while in other places they form part of the normal diet. Insects have a high protein content for their mass, and some authors suggest their potential as a major source of protein in human nutrition.:10–13 In most first-world countries, however, entomophagy (the eating of insects), is taboo. Since it is impossible to entirely eliminate pest insects from the human food chain, insects are inadvertently present in many foods, especially grains. Food safety laws in many countries do not prohibit insect parts in food, but rather limit their quantity. According to cultural materialist anthropologist Marvin Harris, the eating of insects is taboo in cultures that have other protein sources such as fish or livestock.


Scarab beetles held religious and cultural symbolism in Old Egypt, Greece and some shamanistic Old World cultures. The ancient Chinese regarded cicadas as symbols of rebirth or immortality. In Mesopotamian literature, the epic poem of Gilgamesh has allusions to Odonata which signify the impossibility of immortality. Amongst the Aborigines of Australia of the Arrernte language groups, honey ants and witchety grubs served as personal clan totems. In the case of the 'San' bush-men of the Kalahari, it is the praying mantis which holds much cultural significance including creation and zen-like patience in waiting.:9


Even though there is a broad scientific agreement that essentialist and typological conceptualizations of race are untenable, scientists around the world continue to conceptualize race in widely differing ways, some of which have essentialist implications. While some researchers sometimes use the concept of race to make distinctions among fuzzy sets of traits, others in the scientific community suggest that the idea of race often is used in a naive or simplistic way,[page needed] and argue that, among humans, race has no taxonomic significance by pointing out that all living humans belong to the same species, Homo sapiens, and subspecies, Homo sapiens sapiens.


There is a wide consensus that the racial categories that are common in everyday usage are socially constructed, and that racial groups cannot be biologically defined. Nonetheless, some scholars argue that racial categories obviously correlate with biological traits (e.g. phenotype) to some degree, and that certain genetic markers have varying frequencies among human populations, some of which correspond more or less to traditional racial groupings. For this reason, there is no current consensus about whether racial categories can be considered to have significance for understanding human genetic variation.


When people define and talk about a particular conception of race, they create a social reality through which social categorization is achieved. In this sense, races are said to be social constructs. These constructs develop within various legal, economic, and sociopolitical contexts, and may be the effect, rather than the cause, of major social situations. While race is understood to be a social construct by many, most scholars agree that race has real material effects in the lives of people through institutionalized practices of preference and discrimination.


Socioeconomic factors, in combination with early but enduring views of race, have led to considerable suffering within disadvantaged racial groups. Racial discrimination often coincides with racist mindsets, whereby the individuals and ideologies of one group come to perceive the members of an outgroup as both racially defined and morally inferior. As a result, racial groups possessing relatively little power often find themselves excluded or oppressed, while hegemonic individuals and institutions are charged with holding racist attitudes. Racism has led to many instances of tragedy, including slavery and genocide.


In some countries, law enforcement uses race to profile suspects. This use of racial categories is frequently criticized for perpetuating an outmoded understanding of human biological variation, and promoting stereotypes. Because in some societies racial groupings correspond closely with patterns of social stratification, for social scientists studying social inequality, race can be a significant variable. As sociological factors, racial categories may in part reflect subjective attributions, self-identities, and social institutions.


Groups of humans have always identified themselves as distinct from neighboring groups, but such differences have not always been understood to be natural, immutable and global. These features are the distinguishing features of how the concept of race is used today. In this way the idea of race as we understand it today came about during the historical process of exploration and conquest which brought Europeans into contact with groups from different continents, and of the ideology of classification and typology found in the natural sciences.


The European concept of "race", along with many of the ideas now associated with the term, arose at the time of the scientific revolution, which introduced and privileged the study of natural kinds, and the age of European imperialism and colonization which established political relations between Europeans and peoples with distinct cultural and political traditions. As Europeans encountered people from different parts of the world, they speculated about the physical, social, and cultural differences among various human groups. The rise of the Atlantic slave trade, which gradually displaced an earlier trade in slaves from throughout the world, created a further incentive to categorize human groups in order to justify the subordination of African slaves. Drawing on Classical sources and upon their own internal interactions — for example, the hostility between the English and Irish powerfully influenced early European thinking about the differences between people — Europeans began to sort themselves and others into groups based on physical appearance, and to attribute to individuals belonging to these groups behaviors and capacities which were claimed to be deeply ingrained. A set of folk beliefs took hold that linked inherited physical differences between groups to inherited intellectual, behavioral, and moral qualities. Similar ideas can be found in other cultures, for example in China, where a concept often translated as "race" was associated with supposed common descent from the Yellow Emperor, and used to stress the unity of ethnic groups in China. Brutal conflicts between ethnic groups have existed throughout history and across the world.


The first post-Classical published classification of humans into distinct races seems to be François Bernier's Nouvelle division de la terre par les différents espèces ou races qui l'habitent ("New division of Earth by the different species or races which inhabit it"), published in 1684. In the 18th century the differences among human groups became a focus of scientific investigation. But the scientific classification of phenotypic variation was frequently coupled with racist ideas about innate predispositions of different groups, always attributing the most desirable features to the White, European race and arranging the other races along a continuum of progressively undesirable attributes. The 1735 classification of Carl Linnaeus, inventor of zoological taxonomy, divided the human race Homo sapiens into continental varieties of europaeus, asiaticus, americanus, and afer, each associated with a different humour: sanguine, melancholic, choleric, and phlegmatic, respectively. Homo sapiens europaeus was described as active, acute, and adventurous, whereas Homo sapiens afer was said to be crafty, lazy, and careless.


The 1775 treatise "The Natural Varieties of Mankind", by Johann Friedrich Blumenbach proposed five major divisions: the Caucasoid race, Mongoloid race, Ethiopian race (later termed Negroid, and not to be confused with the narrower Ethiopid race), American Indian race, and Malayan race, but he did not propose any hierarchy among the races. Blumenbach also noted the graded transition in appearances from one group to adjacent groups and suggested that "one variety of mankind does so sensibly pass into the other, that you cannot mark out the limits between them".


From the 17th through 19th centuries, the merging of folk beliefs about group differences with scientific explanations of those differences produced what one scholar has called an "ideology of race". According to this ideology, races are primordial, natural, enduring and distinct. It was further argued that some groups may be the result of mixture between formerly distinct populations, but that careful study could distinguish the ancestral races that had combined to produce admixed groups. Subsequent influential classifications by Georges Buffon, Petrus Camper and Christoph Meiners all classified "Negros" as inferior to Europeans. In the United States the racial theories of Thomas Jefferson were influential. He saw Africans as inferior to Whites especially in regards to their intellect, and imbued with unnatural sexual appetites, but described Native Americans as equals to whites.


In the last two decades of the 18th century, the theory of polygenism, the belief that different races had evolved separately in each continent and shared no common ancestor, was advocated in England by historian Edward Long and anatomist Charles White, in Germany by ethnographers Christoph Meiners and Georg Forster, and in France by Julien-Joseph Virey. In the US, Samuel George Morton, Josiah Nott and Louis Agassiz promoted this theory in the mid-nineteenth century. Polygenism was popular and most widespread in the 19th century, culminating in the founding of the Anthropological Society of London (1863) during the period of the American Civil War, in opposition to the Ethnological Society, which had abolitionist sympathies.


Today, all humans are classified as belonging to the species Homo sapiens and sub-species Homo sapiens sapiens. However, this is not the first species of homininae: the first species of genus Homo, Homo habilis, are theorized to have evolved in East Africa at least 2 million years ago, and members of this species populated different parts of Africa in a relatively short time. Homo erectus is theorized to have evolved more than 1.8 million years ago, and by 1.5 million years ago had spread throughout Europe and Asia. Virtually all physical anthropologists agree that Archaic Homo sapiens (A group including the possible species H. heidelbergensis, H. rhodesiensis and H. neanderthalensis) evolved out of African Homo erectus ((sensu lato) or Homo ergaster).


In the early 20th century, many anthropologists accepted and taught the belief that biologically distinct races were isomorphic with distinct linguistic, cultural, and social groups, while popularly applying that belief to the field of eugenics, in conjunction with a practice that is now called scientific racism. After the Nazi eugenics program, racial essentialism lost widespread popularity. Race anthropologists were pressured to acknowledge findings coming from studies of culture and population genetics, and to revise their conclusions about the sources of phenotypic variation. A significant number of modern anthropologists and biologists in the West came to view race as an invalid genetic or biological designation.


Population geneticists have debated whether the concept of population can provide a basis for a new conception of race. In order to do this, a working definition of population must be found. Surprisingly, there is no generally accepted concept of population that biologists use. Although the concept of population is central to ecology, evolutionary biology and conservation biology, most definitions of population rely on qualitative descriptions such as "a group of organisms of the same species occupying a particular space at a particular time" Waples and Gaggiotti identify two broad types of definitions for populations; those that fall into an ecological paradigm, and those that fall into an evolutionary paradigm. Examples of such definitions are:


Traditionally, subspecies are seen as geographically isolated and genetically differentiated populations. That is, "the designation 'subspecies' is used to indicate an objective degree of microevolutionary divergence" One objection to this idea is that it does not specify what degree of differentiation is required. Therefore, any population that is somewhat biologically different could be considered a subspecies, even to the level of a local population. As a result, Templeton has argued that it is necessary to impose a threshold on the level of difference that is required for a population to be designated a subspecies.


This effectively means that populations of organisms must have reached a certain measurable level of difference to be recognised as subspecies. Dean Amadon proposed in 1949 that subspecies would be defined according to the seventy-five percent rule which means that 75% of a population must lie outside 99% of the range of other populations for a given defining morphological character or a set of characters. The seventy-five percent rule still has defenders but other scholars argue that it should be replaced with ninety or ninety-five percent rule.


In 1978, Sewall Wright suggested that human populations that have long inhabited separated parts of the world should, in general, be considered different subspecies by the usual criterion that most individuals of such populations can be allocated correctly by inspection. Wright argued that it does not require a trained anthropologist to classify an array of Englishmen, West Africans, and Chinese with 100% accuracy by features, skin color, and type of hair despite so much variability within each of these groups that every individual can easily be distinguished from every other. However, it is customary to use the term race rather than subspecies for the major subdivisions of the human species as well as for minor ones.


Cladistics is another method of classification. A clade is a taxonomic group of organisms consisting of a single common ancestor and all the descendants of that ancestor. Every creature produced by sexual reproduction has two immediate lineages, one maternal and one paternal. Whereas Carl Linnaeus established a taxonomy of living organisms based on anatomical similarities and differences, cladistics seeks to establish a taxonomy—the phylogenetic tree—based on genetic similarities and differences and tracing the process of acquisition of multiple characteristics by single organisms. Some researchers have tried to clarify the idea of race by equating it to the biological idea of the clade. Often mitochondrial DNA or Y chromosome sequences are used to study ancient human migration paths. These single-locus sources of DNA do not recombine and are inherited from a single parent. Individuals from the various continental groups tend to be more similar to one another than to people from other continents, and tracing either mitochondrial DNA or non-recombinant Y-chromosome DNA explains how people in one place may be largely derived from people in some remote location.


Often taxonomists prefer to use phylogenetic analysis to determine whether a population can be considered a subspecies. Phylogenetic analysis relies on the concept of derived characteristics that are not shared between groups, usually applying to populations that are allopatric (geographically separated) and therefore discretely bounded. This would make a subspecies, evolutionarily speaking, a clade – a group with a common evolutionary ancestor population. The smooth gradation of human genetic variation in general tends to rule out any idea that human population groups can be considered monophyletic (cleanly divided), as there appears to always have been considerable gene flow between human populations. Rachel Caspari (2003) have argued that clades are by definition monophyletic groups (a taxon that includes all descendants of a given ancestor) and since no groups currently regarded as races are monophyletic, none of those groups can be clades.


For the anthropologists Lieberman and Jackson (1995), however, there are more profound methodological and conceptual problems with using cladistics to support concepts of race. They claim that "the molecular and biochemical proponents of this model explicitly use racial categories in their initial grouping of samples". For example, the large and highly diverse macroethnic groups of East Indians, North Africans, and Europeans are presumptively grouped as Caucasians prior to the analysis of their DNA variation. This is claimed to limit and skew interpretations, obscure other lineage relationships, deemphasize the impact of more immediate clinal environmental factors on genomic diversity, and can cloud our understanding of the true patterns of affinity. They argue that however significant the empirical research, these studies use the term race in conceptually imprecise and careless ways. They suggest that the authors of these studies find support for racial distinctions only because they began by assuming the validity of race. "For empirical reasons we prefer to place emphasis on clinal variation, which recognizes the existence of adaptive human hereditary variation and simultaneously stresses that such variation is not found in packages that can be labeled races."


One crucial innovation in reconceptualizing genotypic and phenotypic variation was the anthropologist C. Loring Brace's observation that such variations, insofar as it is affected by natural selection, slow migration, or genetic drift, are distributed along geographic gradations or clines. In part this is due to isolation by distance. This point called attention to a problem common to phenotype-based descriptions of races (for example, those based on hair texture and skin color): they ignore a host of other similarities and differences (for example, blood type) that do not correlate highly with the markers for race. Thus, anthropologist Frank Livingstone's conclusion, that since clines cross racial boundaries, "there are no races, only clines".


In a response to Livingstone, Theodore Dobzhansky argued that when talking about race one must be attentive to how the term is being used: "I agree with Dr. Livingstone that if races have to be 'discrete units,' then there are no races, and if 'race' is used as an 'explanation' of the human variability, rather than vice versa, then the explanation is invalid." He further argued that one could use the term race if one distinguished between "race differences" and "the race concept." The former refers to any distinction in gene frequencies between populations; the latter is "a matter of judgment." He further observed that even when there is clinal variation, "Race differences are objectively ascertainable biological phenomena… but it does not follow that racially distinct populations must be given racial (or subspecific) labels." In short, Livingstone and Dobzhansky agree that there are genetic differences among human beings; they also agree that the use of the race concept to classify people, and how the race concept is used, is a matter of social convention. They differ on whether the race concept remains a meaningful and useful social convention.


In 1964, the biologists Paul Ehrlich and Holm pointed out cases where two or more clines are distributed discordantly—for example, melanin is distributed in a decreasing pattern from the equator north and south; frequencies for the haplotype for beta-S hemoglobin, on the other hand, radiate out of specific geographical points in Africa. As the anthropologists Leonard Lieberman and Fatimah Linda Jackson observed, "Discordant patterns of heterogeneity falsify any description of a population as if it were genotypically or even phenotypically homogeneous".


Patterns such as those seen in human physical and genetic variation as described above, have led to the consequence that the number and geographic location of any described races is highly dependent on the importance attributed to, and quantity of, the traits considered. Scientists discovered a skin-lighting mutation that partially accounts for the appearance of Light skin in humans (people who migrated out of Africa northward into what is now Europe) which they estimate occurred 20,000 to 50,000 years ago. The East Asians owe their relatively light skin to different mutations. On the other hand, the greater the number of traits (or alleles) considered, the more subdivisions of humanity are detected, since traits and gene frequencies do not always correspond to the same geographical location. Or as Ossorio & Duster (2005) put it:


Coop et al. (2009) found "a selected allele that strongly differentiates the French from both the Yoruba and Han could be strongly clinal across Europe, or at high frequency in Europe and absent elsewhere, or follow any other distribution according to the geographic nature of the selective pressure. However, we see that the global geographic distributions of these putatively selected alleles are largely determined simply by their frequencies in Yoruba, French and Han (Figure 3). The global distributions fall into three major geographic patterns that we interpret as non-African sweeps, west Eurasian sweeps and East Asian sweeps, respectively."


Another way to look at differences between populations is to measure genetic differences rather than physical differences between groups. The mid-20th-century anthropologist William C. Boyd defined race as: "A population which differs significantly from other populations in regard to the frequency of one or more of the genes it possesses. It is an arbitrary matter which, and how many, gene loci we choose to consider as a significant 'constellation'". Leonard Lieberman and Rodney Kirk have pointed out that "the paramount weakness of this statement is that if one gene can distinguish races then the number of races is as numerous as the number of human couples reproducing." Moreover, the anthropologist Stephen Molnar has suggested that the discordance of clines inevitably results in a multiplication of races that renders the concept itself useless. The Human Genome Project states "People who have lived in the same geographic region for many generations may have some alleles in common, but no allele will be found in all members of one population and in no members of any other."


The population geneticist Sewall Wright developed one way of measuring genetic differences between populations known as the Fixation index, which is often abbreviated to FST. This statistic is often used in taxonomy to compare differences between any two given populations by measuring the genetic differences among and between populations for individual genes, or for many genes simultaneously. It is often stated that the fixation index for humans is about 0.15. This translates to an estimated 85% of the variation measured in the overall human population is found within individuals of the same population, and about 15% of the variation occurs between populations. These estimates imply that any two individuals from different populations are almost as likely to be more similar to each other than either is to a member of their own group. Richard Lewontin, who affirmed these ratios, thus concluded neither "race" nor "subspecies" were appropriate or useful ways to describe human populations. However, others have noticed that group variation was relatively similar to the variation observed in other mammalian species.


Wright himself believed that values >0.25 represent very great genetic variation and that an FST of 0.15–0.25 represented great variation. However, about 5% of human variation occurs between populations within continents, therefore FST values between continental groups of humans (or races) of as low as 0.1 (or possibly lower) have been found in some studies, suggesting more moderate levels of genetic variation. Graves (1996) has countered that FST should not be used as a marker of subspecies status, as the statistic is used to measure the degree of differentiation between populations, although see also Wright (1978).


Jeffrey Long and Rick Kittles give a long critique of the application of FST to human populations in their 2003 paper "Human Genetic Diversity and the Nonexistence of Biological Races". They find that the figure of 85% is misleading because it implies that all human populations contain on average 85% of all genetic diversity. They claim that this does not correctly reflect human population history, because it treats all human groups as independent. A more realistic portrayal of the way human groups are related is to understand that some human groups are parental to other groups and that these groups represent paraphyletic groups to their descent groups. For example, under the recent African origin theory the human population in Africa is paraphyletic to all other human groups because it represents the ancestral group from which all non-African populations derive, but more than that, non-African groups only derive from a small non-representative sample of this African population. This means that all non-African groups are more closely related to each other and to some African groups (probably east Africans) than they are to others, and further that the migration out of Africa represented a genetic bottleneck, with much of the diversity that existed in Africa not being carried out of Africa by the emigrating groups. This view produces a version of human population movements that do not result in all human populations being independent; but rather, produces a series of dilutions of diversity the further from Africa any population lives, each founding event representing a genetic subset of its parental population. Long and Kittles find that rather than 85% of human genetic diversity existing in all human populations, about 100% of human diversity exists in a single African population, whereas only about 70% of human genetic diversity exists in a population derived from New Guinea. Long and Kittles argued that this still produces a global human population that is genetically homogeneous compared to other mammalian populations.


In his 2003 paper, "Human Genetic Diversity: Lewontin's Fallacy", A. W. F. Edwards argued that rather than using a locus-by-locus analysis of variation to derive taxonomy, it is possible to construct a human classification system based on characteristic genetic patterns, or clusters inferred from multilocus genetic data. Geographically based human studies since have shown that such genetic clusters can be derived from analyzing of a large number of loci which can assort individuals sampled into groups analogous to traditional continental racial groups. Joanna Mountain and Neil Risch cautioned that while genetic clusters may one day be shown to correspond to phenotypic variations between groups, such assumptions were premature as the relationship between genes and complex traits remains poorly understood. However, Risch denied such limitations render the analysis useless: "Perhaps just using someone's actual birth year is not a very good way of measuring age. Does that mean we should throw it out? ... Any category you come up with is going to be imperfect, but that doesn't preclude you from using it or the fact that it has utility."


Early human genetic cluster analysis studies were conducted with samples taken from ancestral population groups living at extreme geographic distances from each other. It was thought that such large geographic distances would maximize the genetic variation between the groups sampled in the analysis and thus maximize the probability of finding cluster patterns unique to each group. In light of the historically recent acceleration of human migration (and correspondingly, human gene flow) on a global scale, further studies were conducted to judge the degree to which genetic cluster analysis can pattern ancestrally identified groups as well as geographically separated groups. One such study looked at a large multiethnic population in the United States, and "detected only modest genetic differentiation between different current geographic locales within each race/ethnicity group. Thus, ancient geographic ancestry, which is highly correlated with self-identified race/ethnicity—as opposed to current residence—is the major determinant of genetic structure in the U.S. population." (Tang et al. (2005))


Witherspoon et al. (2007) have argued that even when individuals can be reliably assigned to specific population groups, it may still be possible for two randomly chosen individuals from different populations/clusters to be more similar to each other than to a randomly chosen member of their own cluster. They found that many thousands of genetic markers had to be used in order for the answer to the question "How often is a pair of individuals from one population genetically more dissimilar than two individuals chosen from two different populations?" to be "never". This assumed three population groups separated by large geographic ranges (European, African and East Asian). The entire world population is much more complex and studying an increasing number of groups would require an increasing number of markers for the same answer. The authors conclude that "caution should be used when using geographic or genetic ancestry to make inferences about individual phenotypes." Witherspoon, et al. concluded that, "The fact that, given enough genetic data, individuals can be correctly assigned to their populations of origin is compatible with the observation that most human genetic variation is found within populations, not between them. It is also compatible with our ﬁnding that, even when the most distinct populations are considered and hundreds of loci are used, individuals are frequently more similar to members of other populations than to members of their own population."


Anthropologists such as C. Loring Brace, the philosophers Jonathan Kaplan and Rasmus Winther, and the geneticist Joseph Graves,[page needed] have argued that while there it is certainly possible to find biological and genetic variation that corresponds roughly to the groupings normally defined as "continental races", this is true for almost all geographically distinct populations. The cluster structure of the genetic data is therefore dependent on the initial hypotheses of the researcher and the populations sampled. When one samples continental groups, the clusters become continental; if one had chosen other sampling patterns, the clustering would be different. Weiss and Fullerton have noted that if one sampled only Icelanders, Mayans and Maoris, three distinct clusters would form and all other populations could be described as being clinally composed of admixtures of Maori, Icelandic and Mayan genetic materials. Kaplan and Winther therefore argue that, seen in this way, both Lewontin and Edwards are right in their arguments. They conclude that while racial groups are characterized by different allele frequencies, this does not mean that racial classification is a natural taxonomy of the human species, because multiple other genetic patterns can be found in human populations that crosscut racial distinctions. Moreover, the genomic data underdetermines whether one wishes to see subdivisions (i.e., splitters) or a continuum (i.e., lumpers). Under Kaplan and Winther's view, racial groupings are objective social constructions (see Mills 1998 ) that have conventional biological reality only insofar as the categories are chosen and constructed for pragmatic scientific reasons. In earlier work, Winther had identified "diversity partitioning" and "clustering analysis" as two separate methodologies, with distinct questions, assumptions, and protocols. Each is also associated with opposing ontological consequences vis-a-vis the metaphysics of race.


Many social scientists have replaced the word race with the word "ethnicity" to refer to self-identifying groups based on beliefs concerning shared culture, ancestry and history. Alongside empirical and conceptual problems with "race", following the Second World War, evolutionary and social scientists were acutely aware of how beliefs about race had been used to justify discrimination, apartheid, slavery, and genocide. This questioning gained momentum in the 1960s during the U.S. civil rights movement and the emergence of numerous anti-colonial movements worldwide. They thus came to believe that race itself is a social construct, a concept that was believed to correspond to an objective reality but which was believed in because of its social functions.


Craig Venter and Francis Collins of the National Institute of Health jointly made the announcement of the mapping of the human genome in 2000. Upon examining the data from the genome mapping, Venter realized that although the genetic variation within the human species is on the order of 1–3% (instead of the previously assumed 1%), the types of variations do not support notion of genetically defined races. Venter said, "Race is a social concept. It's not a scientific one. There are no bright lines (that would stand out), if we could compare all the sequenced genomes of everyone on the planet." "When we try to apply science to try to sort out these social differences, it all falls apart."


The theory that race is merely a social construct has been challenged by the findings of researchers at the Stanford University School of Medicine, published in the American Journal of Human Genetics as "Genetic Structure, Self-Identified Race/Ethnicity, and Confounding in Case-Control Association Studies". One of the researchers, Neil Risch, noted: "we looked at the correlation between genetic structure [based on microsatellite markers] versus self-description, we found 99.9% concordance between the two. We actually had a higher discordance rate between self-reported sex and markers on the X chromosome! So you could argue that sex is also a problematic category. And there are differences between sex and gender; self-identification may not be correlated with biology perfectly. And there is sexism."


Basically, race in Brazil was "biologized", but in a way that recognized the difference between ancestry (which determines genotype) and phenotypic differences. There, racial identity was not governed by rigid descent rule, such as the one-drop rule, as it was in the United States. A Brazilian child was never automatically identified with the racial type of one or both parents, nor were there only a very limited number of categories to choose from, to the extent that full siblings can pertain to different racial groups.


Over a dozen racial categories would be recognized in conformity with all the possible combinations of hair color, hair texture, eye color, and skin color. These types grade into each other like the colors of the spectrum, and not one category stands significantly isolated from the rest. That is, race referred preferentially to appearance, not heredity, and appearance is a poor indication of ancestry, because only a few genes are responsible for someone's skin color and traits: a person who is considered white may have more African ancestry than a person who is considered black, and the reverse can be also true about European ancestry. The complexity of racial classifications in Brazil reflects the extent of miscegenation in Brazilian society, a society that remains highly, but not strictly, stratified along color lines. These socioeconomic factors are also significant to the limits of racial lines, because a minority of pardos, or brown people, are likely to start declaring themselves white or black if socially upward, and being seen as relatively "whiter" as their perceived social status increases (much as in other regions of Latin America).


Fluidity of racial categories aside, the "biologification" of race in Brazil referred above would match contemporary concepts of race in the United States quite closely, though, if Brazilians are supposed to choose their race as one among, Asian and Indigenous apart, three IBGE's census categories. While assimilated Amerindians and people with very high quantities of Amerindian ancestry are usually grouped as caboclos, a subgroup of pardos which roughly translates as both mestizo and hillbilly, for those of lower quantity of Amerindian descent a higher European genetic contribution is expected to be grouped as a pardo. In several genetic tests, people with less than 60-65% of European descent and 5-10% of Amerindian descent usually cluster with Afro-Brazilians (as reported by the individuals), or 6.9% of the population, and those with about 45% or more of Subsaharan contribution most times do so (in average, Afro-Brazilian DNA was reported to be about 50% Subsaharan African, 37% European and 13% Amerindian).


If a more consistent report with the genetic groups in the gradation of miscegenation is to be considered (e.g. that would not cluster people with a balanced degree of African and non-African ancestry in the black group instead of the multiracial one, unlike elsewhere in Latin America where people of high quantity of African descent tend to classify themselves as mixed), more people would report themselves as white and pardo in Brazil (47.7% and 42.4% of the population as of 2010, respectively), because by research its population is believed to have between 65 and 80% of autosomal European ancestry, in average (also >35% of European mt-DNA and >95% of European Y-DNA).