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top 10 words in brain distribution (in article): animal horse species wear breed cat wolf human hunt male |
top 10 words in brain distribution (in article): plant power species seed animal water leaf food common variety |
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top 10 words in brain distribution (not in article): fruit grow produce station tree flower train sugar line signal |
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| The dog'" ("Canis lupus familiaris",) is a domesticated subspecies of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The domestic dog has been one of the most widely kept working and companion animals in human history. The domestication of the gray wolf took place in a handful of events roughly 15,000 years ago in central Asia. The dog quickly became ubiquitous across culture in all parts of the world, and was extremely valuable to early human settlements. For instance, it is believed that the successful emigration across the Bering Strait might not have been possible without sled dogs. As a result of the domestication process, the dog developed a sophisticated intelligence that includes unparalleled social cognition and a simple theory of mind that is important to their interaction with humans. These social skills have helped the dog to perform in myriad roles, such as hunting, herding, protection, and, more recently, assisting handicapped individuals. Currently, there are estimated to be 400 million dogs in the world. Over the 15,000 year span that the dog had been domesticated, it diverged into only a handful of landraces, groups of similar animals whose morphology and behavior have been shaped by environmental factors and functional roles. Humans did not take an active, intentional role in this process until the last few hundred years. As the modern understanding of genetics developed, humans began to intentionally breed dogs for a wide range of specific traits. Through this process, the dog has developed into hundreds of varied breeds, and shows more behavioral and morphological variation than any other land mammal. For example, height measured to the withers ranges from a few inches in the Chihuahua to a few feet in the Irish Wolfhound; color varies from white through grays (usually called "blue'") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth. It is common for most breeds to shed this coat, but non-shedding breeds are also popular. Etymology and related terminology. "Dog" is the common use term that refers to members of the subspecies "Canis lupus familiaris". The term is sometimes used to refer to a wider range of species: it can be used to refer to any mammal belonging to the family Canidae, which includes wolves, foxes, jackals, and coyotes; it can be used to refer to the subfamily of Caninae, or the genus Canis, also often called the "true dogs". Some members of the family have "dog" in their common names, such as the raccoon dog and the African wild dog. A few animals have "dog" in their common names but are not canids, such as the prairie dog and the dog fish. The English word "dog" can be traced back to the Old English "docga", a "powerful breed of canine". The term may derive from Proto-Germanic "*dukkōn", represented in Old English "finger-docce" ("finger-muscle"). Due to the linguistically archaic structure of the word, the term "dog" may ultimately derive from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal. The English word "hound", which refers to a specific breed group in English, means "dog" in general in other Germanic languages; it is cognate to German "hund", Dutch "hond", common Scandinavian "hund", and Icelandic "hundur". "Hound" itself is derived from the Proto-Indo-European "*kwon-", which is also the direct root of the Greek κυων (kuōn) and the indirect root of the Latin "canis" through the variant form "*kani-". In breeding circles, a male canine is referred to as a "dog", while a female is called a "bitch". A group of offspring is a "litter". The father of a litter is called the "sire", and the mother is called the "dam". Offspring are generally called "pups" or "puppies" until they are about a year old. The process of birth is "whelping". Taxonomy and evolution. The domestic dog was originally classified as "Canis familiaris" and "Canis familiarus domesticus" by Linnaeus in 1758, and is currently classified as "Canis lupus familiaris", a subspecies of the gray wolf "Canis lupus", by the Smithsonian Institution and the American Society of Mammalogists. Overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species, the gray wolf, is the common ancestor for all breeds of domestic dogs, however the timeframe and mechanisms by which dogs diverged are controversial. The current consensus among biologists and archaeologists is that no one can be sure when dogs were domesticated. There is conclusive evidence that dogs genetically diverged from their wolf ancestors at least 15,000 years ago but most believe domestication to have occurred much earlier. The evidence cited for an earlier divergence comes from archaeological findings and mitochondrial DNA studies, both of which are inconclusive. The archaeological evidence demonstrates that the domestication of dogs occurred prior to 15,000 years ago. Some genetic evidence indicates that the domestication of dogs from their wolf ancestors began in the late Upper Paleolithic close to the Pleistocene Holocene boundary, between 17,000 and 14,000 years ago. The earliest dog fossils, two large skulls from Russia and a mandible from Germany, date from roughly 14,000 years ago. Their likely ancestor is the large Eurasian wolf ("Canis lupus lupus"). Remains of smaller dogs from Natufian cave deposits in the Middle East have been dated to around 10,000 to 12,000 years ago. There is a great deal of archealogical evidence for dogs throughout Europe and Asia around this period and through the next two thousand years (roughly 8,000 to 10,000 years ago), with fossils uncovered in Germany, the French Alps, and Iraq, and cave paintings in Turkey. DNA studies have provided a wider range of possible divergence dates, from 15,000 to 40,000 years ago, to as much as 100,000 to 140,000 years ago. This evidence depends on a number of assumptions that others claim are violated. Genetic studies are based in comparisons of genetic diversity between species, and depend on a calibration date, such as the wolf-coyote divergence date, which is estimated to be roughly 1 million years ago. If this divergence date is closer to 750,000 or 2 million years ago, then genetic analyses would be interpreted very differently. Furthermore, it is believed that the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding, which could bias DNA analyses to support an earlier divergence. The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence, assumes that hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines. Genetic analyses indicate all dogs are likely descended from a handful of domestication events with a small number of founding females, although there is evidence that domesticated dogs interbred with local populations of wild wolves on several occasions. Data suggests that dogs first diverged from wolves in East Asia, and that these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 B.C. The oldest groups of dogs, which show the greatest genetic variability and are the most similar to their wolf ancestors, are primarily Asian and African breeds, including the Basenji, Saluki, Afghan Hound, Tibetan Terrier, Lhasa Apso, Chow Chow, Pekingese, Shar-Pei, Shi Tzu, Akita, Shiba Inu, Alaskan Malamute, Siberian Husky, and Samoyed. Some breeds that were thought to be very old, such as the Pharaoh Hound, Ibizan Hound, and Norwegian Elkhound, are now known to have been recreated more recently. There is a great deal of controversy surrounding the evolutionary framework for the domestication of dogs. At least three early species of the "Homo" genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable period in contact with canine species. Despite this, there is no evidence of any adaptation of these canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agriculture. This has led some biologists to suggest that one of the forces that led to the domestication of dogs was a shift in human lifestyle in the form of established human settlements. Permanent settlements would have coincided with a greater amount of disposable food and would have created a barrier between wild and anthropogenic canine populations. Biology. Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Nevertheless, their morphology is based on that of their wild ancestors, gray wolves. Dogs are predators and scavengers, and like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing. Dogs are highly variable in height and weight. The smallest known dog was a Yorkshire Terrier, who stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.75 in) in length along the head-and-body, and weighed only 113 grams (4 ounces). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lbs) and was 250 cm (8.2 feet) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (42.2 in) at the shoulder. Sight. The dog's visual system is engineered to serve the purposes of a hunter. While a dog's visual acuity is poor (that of a poodle's has been estimated to translate to a Snellen rating of 20 75), their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (i.e., identifying their owner) from distances up to a mile. As crepuscular hunters, dogs often rely on their vision in low light situations: they have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum. The tapetum is a reflective surface behind the retina that reflects light back to give the photoreceptors a second chance to catch the photons. Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness in humans. The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations. Many long-nosed breeds have a "visual streak" — a wide foveal region that runs across the width of the retina and gives them a very wide field of excellent vision. Some long-muzzled breeds, particularly the sighthounds, have a field of vision up to 270° (compared to 180° for humans). Short-nosed breeds, on the other hand, have an "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans. Most breeds have good vision, but some show a genetic predisposition for myopia — such as Rottweilers, where one out of every two has been found to be myopic. Hearing. The frequency range of dog hearing is approximately 40 Hz to 60,000 Hz, which means that dogs can detect sounds outside both ends of the human auditory spectrum. Additionally, dogs have ear mobility which allows them to rapidly pinpoint the exact location of a sound. Eighteen or more muscles can tilt, rotate, raise, or lower a dog's ear. A dog can identify a sound's location much faster than a human can, as well as hear sounds at four times the distance. Smell. While the human brain is dominated by a large visual cortex, the dog brain is largely dominated by an olfactory cortex. The olfactory bulb in dogs is roughly forty times bigger than the olfactory bulb in humans, relative to total brain size, with 125 to 220 million smell-sensitive receptors. The bloodhound exceeds this standard with nearly 300 million receptors. Dogs can discriminate odors at concentrations nearly 100 million times lower than humans can. Coat. The coats of domestic dogs are either "double", made up of a coarse topcoat and a soft undercoat, like a wolf, or "single", with the topcoat only. Dogs with double coats tend to originate in colder climates. Domestic dogs often display the remnants of countershading, a common natural camouflage pattern. The general theory of countershading is that an animal that is lit from above will appear lighter on its upper half and darker on its lower half, where it will usually be in its own shade. This is a pattern that predators can learn to watch for. A countershaded animal will have dark coloring on its upper surfaces and light coloring below, which reduces its general visibility. Thus many breeds will have an occasional "blaze", stripe, or "star" of white fur on their chest or underside. Tail. There are many different shapes for dog tails: straight, straight up, sickle, curled, or cork-screw. In some breeds, the tail is traditionally docked to avoid injuries (especially for hunting dogs). In some breeds, puppies can be born with a short tail or no tail at all. This occurs more frequently in those breeds that are frequently docked and thus have no breed standard regarding the tail. Types and breeds. While all dogs are genetically very similar, natural selection and selective breeding have reinforced certain characteristics in certain populations of dogs, giving rise to dog types and dog breeds. Dog types are broad categories based on function, genetics, or characteristics. Dog breeds are groups of animals that possess a set of inherited characteristics that distinguishes them from other animals within the same species. Modern dog breeds are non-scientific classifications of dogs kept by modern kennel clubs. Purebred dogs of one breed are genetically distinguishable from purebred dogs of other breeds, but the means by which kennel clubs classify dogs is unsystematic. Systematic analyses of the dog genome has revealed only four major types of dogs that can be said to be statistically distinct. These include the "old world dogs" (e.g., Malamute and Shar-Pei), "Mastiff"-type (e.g., Labrador Retriever), "herding"-type (e.g., St. Bernard), and "all others" (also called "modern"- or "hunting"-type). Health. Dogs are susceptible to various diseases, ailments, and poisons, some of which can affect humans. To defend against many common diseases, dogs are often vaccinated. Some breeds of dogs are prone to certain genetic ailments such as elbow or hip dysplasia, blindness, deafness, pulmonic stenosis, cleft palate, and trick knees. Two serious medical conditions particularly affecting dogs are pyometra, affecting unspayed females of all types and ages, and bloat, which affects the larger breeds or deep-chested dogs. Both of these are acute conditions, and can kill rapidly. Dogs are also susceptible to parasites such as fleas, ticks, and mites, as well as hookworms, tapeworms, roundworms, and heartworms. Dogs are also vulnerable to some of the same health conditions as humans, including diabetes, dental and heart disease, epilepsy, cancer, hypothyroidism, and arthritis. Mortality. The typical lifespan of dogs varies widely among breeds, but for most the median longevity, the age at which half the dogs in a population have died and half are still alive, ranges from 10 to 13 years. Individual dogs may live well beyond the median of their breed. The breed with the shortest lifespan (among breeds for which there is a questionnaire survey with a reasonable sample size) is the Dogue de Bordeaux, with a median longevity of about 5.2 years, but several breeds, including Miniature Bull Terriers, Bulldogs, Nova Scotia Duck-Tolling Retrievers, Bloodhounds, Irish Wolfhounds, Greater Swiss Mountain Dogs, Great Danes, and Mastiffs, are nearly as short-lived, with median longevities of 6 to 7 years. The longest-lived breeds, including Toy Poodles, Border Terriers, Miniature Dachshunds, Miniature Poodles, and Tibetan Spaniels, have median longevities of 14 to 15 years. The median longevity of mixed breed dogs, taken as an average of all sizes, is one or more years longer than that of purebred dogs when all breeds are averaged. The dog widely reported to be the longest-lived is "Bluey," who died in 1939 and was claimed to be 29.5 years old at the time of his death; however, the Bluey record is anecdotal and unverified. The longest verified records are of dogs living for 24 years. Predation. Although wild dogs, like wolves, are apex predators, they can be killed in territory disputes with wild animals. Furthermore, in areas where both dogs | Beetles'" are the group of insects with the largest number of known species. They are placed in the order "'Coleoptera'" (from Greek, "koleos", "sheath"; and, "pteron", "wing", thus "sheathed wing"), which contains more described species than in any other order in the animal kingdom, constituting about 25% of all known life-forms. 40% of all described insect species are beetles (about 350,000 species), and new species are frequently discovered. Estimates put the total number of species, described and undescribed, at between 5 and 8 million. Beetles can be found in almost all habitats, but are not known to occur in the sea or in the polar regions. They interact with their ecosystems in several ways. They often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are prey of various animals including birds and mammals. Certain species are agricultural pests, such as the Colorado potato beetle "Leptinotarsa decemlineata", the boll weevil "Anthonomus grandis", the red flour beetle "Tribolium castaneum", and the mungbean or cowpea beetle "Callosobruchus maculatus", while other species of beetles are important controls of agricultural pests. For example, beetles in the family Coccinellidae ("ladybirds" or "ladybugs") consume aphids, scale insects, thrips, and other plant-sucking insects that damage crops. Description. The name "Coleoptera" was given by Aristotle for the hardened shield-like forewing (coleo= shield+ ptera= wing). Other characters of this group which are believed to be monophyletic include a holometabolous life cycle; having a prothorax that is distinct from and freely articulating with the mesothorax; the meso- and meta-thoracic segments fusing to form a pterothorax; a depressed body shape with the legs on the ventral surface; the coxae of legs recessed into cavities formed by heavily sclerotized thoracic sclerites; the abdominal sternites more sclerotized than the tergites; antennae with 11 or fewer segments; and terminal genitalic appendages retracted into the abdomen and invisible at rest. The general anatomy of beetles is quite uniform, although specific organs and appendages may vary greatly in appearance and function between the many families in the order. Like all insects, beetles' bodies are divided into three sections: the head, the thorax, and the abdomen. When viewed from below, the thorax is that part from which all three pairs of legs and both pairs of wings arise. The abdomen is everything posterior to the thorax. When viewed from above, most beetles appear to have three clear sections, but this is deceptive: on the beetle's upper surface, the middle "section" is a hard plate called the pronotum, which is only the front part of the thorax; the back part of the thorax is concealed by the beetle's wings. Like all arthropods, beetles are segmented organisms, and all three of the major sections of the body are themselves composed of several further segments, although these are not always readily discernible. This further segmentation is usually best seen on the abdomen. Beetles are generally characterised by a particularly hard exoskeleton and hard forewings (elytra). The beetle's exoskeleton is made up of numerous plates called sclerites, separated by thin sutures. This design creates the armoured defences of the beetle while maintaining flexibility. The elytra are not used for flight, but tend to cover the hind part of the body and protect the second pair of wings ("alae"). The elytra must be raised in order to move the hind flight wings. A beetle's flight wings are crossed with veins and are folded after landing, often along these veins, and are stored below the elytra. In some beetles, the ability to fly has been lost. These include the ground beetles (family Carabidae) and some "true weevils" (family Curculionidae), but also some desert and cave-dwelling species of other families. Many of these species have the two elytra fused together, forming a solid shield over the abdomen. In a few families, both the ability to fly and the elytra have been lost, with the best known example being the glow-worms of the family Phengodidae, in which the females are larviform throughout their lives. Beetles have mouthparts similar to those of grasshoppers. Of these parts, the most commonly known are probably the mandibles, which appear as large pincers on the front of some beetles. The mandibles are a pair of hard, often tooth-like structures that move horizontally to grasp, crush, or cut food or enemies (see defence, below). Two pairs of finger-like appendages are found around the mouth in most beetles, serving to move food into the mouth. These are the maxillary and labial palpi. The eyes are compound and may display remarkable adaptability, as in the case of whirligig beetles (family Gyrinidae), in which the eyes are split to allow a view both above and below the waterline. Other species also have divided eyes — some longhorn beetles (family Cerambycidae) and weevils — while many beetles have eyes that are notched to some degree. A few beetle genera also possess ocelli, which are small, simple eyes usually situated farther back on the head (on the vertex). Beetles' antennae are primarily organs of smell, but may also be used to feel out a beetle's environment physically. They may also be used in some families during mating, or among a few beetles for defence. Antennae vary greatly in form within the Coleoptera, but are often similar within any given family. In some cases, males and females of the same species will have different antennal forms. Antennae may be clavate (flabellate and lamellate are sub-forms of clavate, or clubbed antennae), filiform, geniculate, moniliform, pectinate, or serrate. For images of these antennal forms see antenna (biology). The legs, which are multi-segmented, end in two to five small segments called tarsi. Like many other insect orders beetles bear claws, usually one pair, on the end of the last tarsal segment of each leg. While most beetles use their legs for walking, legs may be variously modified and adapted for other uses. Among aquatic families — Dytiscidae, Haliplidae, many species of Hydrophilidae and others — the legs, most notably the last pair, are modified for swimming and often bear rows of long hairs to aid this purpose. Other beetles have fossorial legs that are widened and often spined for digging. Species with such adaptations are found among the scarabs, ground beetles, and clown beetles (family Histeridae). The hind legs of some beetles, such as flea beetles (within Chrysomelidae) and flea weevils (within Curculionidae), are enlarged and designed for jumping. Oxygen is obtained via a tracheal system. Air enters a series of tubes along the body through openings called spiracles, and is then taken into increasingly finer fibres. Pumping movements of the body force the air through the system. Beetles have hemolymph instead of blood, and the open circulatory system of the beetle is powered by a tube-like heart attached to the top inside of the thorax. Development. Beetles are endopterygotes with complete metamorphosis. A single female may lay from several dozen to several thousand eggs during her lifetime. Eggs are usually laid according to the substrate the larva will feed on upon hatching. Among others, they can be laid loose in the substrate (e.g. flour beetle), laid in clumps on leaves (e.g. Colorado potato beetle), or individually attached (e.g. mungbean beetle and other seed borers) or buried in the medium (e.g. carrot weevil). The larva is usually the principal feeding stage of the beetle life cycle. Larvae tend to feed voraciously once they emerge from their eggs. Some feed externally on plants, such as those of certain leaf beetles, while others feed within their food sources. Examples of internal feeders are most Buprestidae and longhorn beetles. The larvae of many beetle families are predatory like the adults (ground beetles, ladybirds, rove beetles). The larval period varies between species but can be as long as several years. Beetle larvae can be differentiated from other insect larvae by their hardened, often darkened head, the presence of chewing mouthparts, and spiracles along the sides of the body. Like adult beetles, the larvae are varied in appearance, particularly between beetle families. Beetles whose larvae are somewhat flattened and are highly mobile are the ground beetles, some rove beetles, and others; their larvae are described as campodeiform. Some beetle larvae resemble hardened worms with dark head capsules and minute legs. These are elateriform larvae, and are found in the click beetle (Elateridae) and darkling beetle (Tenebrionidae) families. Some elateriform larvae of click beetles are known as wireworms. Beetles in the families of the Scarabaeoidea have short, thick larvae described as scarabaeiform, but more commonly known as grubs. All beetle larvae go through several instars, which are the developmental stages between each moult. In many species the larvae simply increase in size with each successive instar as more food is consumed. In some cases, however, more dramatic changes occur. Among certain beetle families or genera, particularly those that exhibit parasitic lifestyles, the first instar (the planidium) is highly mobile in order to search out a host, while the following instars are more sedentary and remain on or within their host. This is known as hypermetamorphosis; examples include the blister beetles (family Meloidae) and some rove beetles, particularly those of the genus "Aleochara". As with all endopterygotes, beetle larvae pupate, and from this pupa emerges a fully formed, sexually mature adult beetle, or imago. Adults have an extremely variable lifespan, from weeks to years, depending on the species. Reproduction. Beetles may display extremely intricate behaviour when mating. Pheromone communication is thought to be important in the location of a mate. Conflict can play a part in the mating rituals of species such as burying beetles (genus "Nicrophorus") where conflicts between males and females rage until only one of each is left, thus ensuring reproduction by the strongest and fittest. Many male beetles are territorial and will fiercely defend their small patch of territory from intruding males. In such species, the males may often have horns on the head and or thorax, making their overall body lengths greater than those of the females, unlike most insects. Pairing is generally short but in some cases will last for several hours. During pairing sperm cells are transferred to the female to fertilise the egg. Parental care varies between species, ranging from the simple laying of eggs under a leaf to certain scarab beetles, which construct underground structures complete with a supply of dung to house and feed their young. Other beetles are leaf rollers, biting sections of leaves to cause them to curl inwards, then laying their eggs, thus protected, inside. Defense. Beetles and their larvae have a variety of strategies to avoid being attacked by predators or parasitoids. These include camouflage, mimicry, toxicity, and active defense. Camouflage involves the use of colouration 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 coloured 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. Another defence that often uses colour 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. This defence can be found to a lesser extent in other beetle families, such as the scarab beetles. Beetles may combine their colour mimicry with behavioural mimicry, acting like the wasps they already closely resemble. Many beetle species, including ladybirds, blister beetles, and lycid beetles can secrete distasteful or toxic substances to make them unpalatable or even poisonous. These same species often exhibit aposematism, where bright or contrasting colour patterns warn away potential predators, and there are, not surprisingly, a great many beetles and other insects that mimic these chemically-protected species. Large ground beetles and longhorn beetles may defend themselves using strong mandibles and or spines or horns to forcibly persuade a predator to seek out easier prey. Others, such as bombardier beetles (within Carabidae), may spray chemicals from their abdomen to repel predators. Feeding. Besides being abundant and varied, the Coleoptera are able to exploit the wide diversity of food sources available in their many habitats. Some are omnivores, eating both plants and animals. Other beetles are highly specialised in their diet. Many species of leaf beetles, longhorn beetles, and weevils are very host specific, feeding on only a single species of plant. Ground beetles and rove beetles (family Staphylinidae), among others, are primarily carnivorous and will catch and consume many other arthropods and small prey such as earthworms and snails. While most predatory beetles are generalists, a few species have more specific prey requirements or preferences. Decaying organic matter is a primary diet for many species. This can range from dung, which is consumed by coprophagous species such as certain scarab beetles (family Scarabaeidae), to dead animals, which are eaten by necrophagous species such as the carrion beetles (family Silphidae). Some of the beetles found within dung and carrion are in fact predatory, such as the clown beetles, preying on the larvae of coprophagous and necrophagous insects. Adaptations to the environment. Aquatic beetles use several techniques for retaining air beneath the water's surface. Beetles of the family Dytiscidae hold air between the abdomen and the elytra when diving. Hydrophilidae have hairs on their under surface that retain a layer of air against their bodies. Adult crawling water beetles use both their elytra and their hind coxae (the basal segment of the back legs) in air retention while whirligig beetles simply carry an air bubble down with them whenever they dive. Evolutionary history and classification. While some authorities believe modern beetles began about 140 million years ago, research announced in 2007 showed that beetles may have entered the fossil record during the Lower Permian, about 265 to 300 million years ago. The four extant suborders of beetle are these: These suborders diverged in the Permian and Triassic. Their phylogenetic relationship is uncertain, with the most popular hypothesis being that Polyphaga and Myxophaga are most closely related, with Adephaga as the sister group to those two, and Archostemata as sister to the other three collectively. There are about 350,000 species of beetles. Such a large number of species poses special problems for classification, with some families consisting of thousands of species and needing further division into subfamilies and tribes. Pests. Many agricultural, forestry, and household insect pests are beetles. These include the following: Beneficial organisms. Some farmers develop beetle banks to foster and provide cover for beneficial beetles. Beetles of the Dermestidae family are often used in taxidermy to clean bones of remaining flesh. Beetles in ancient Egypt and other cultures. Several species of dung beetle, most notably "Scarabaeus sacer" (often referred to as "scarab"), enjoyed a sacred status among the ancient Egyptians, as the creatures were likened to the major god Khepri. Some scholars suggest that the Egyptians' practice of making mummies was inspired by the brooding process of the beetle. Many thousands of amulets and stamp seals have been excavated that depict the scarab. In many artifacts, the scarab is depicted pushing the sun along its course in the sky, much as scarabs push or roll balls of dung to their brood sites. During and following the New Kingdom, scarab amulets were often placed over the heart of the mummified deceased. Some tribal groups, particularly in tropical parts of the world, use the colourful, iridescent elytra of certain beetles, especially certain Scarabaeidae, in ceremonies and as adornment. Study and collection. The study of beetles is called coleopterology'" (from "Coleoptera", see above, and Greek, "-logia"), and its practitioners are "coleopterists" (see this list). Coleopterists have formed organisations to facilitate the study of beetles. Among these is The Coleopterists Society, an international organisation based in the United States. Such organisations may have both professionals and amateurs interested in beetles as members. Research in this field is often published in peer-reviewed journals specific to the field of coleopterology, though journals dealing with general entomology also publish many papers on various aspects of beetle biology. Some of the journals specific to beetle research are: There is a thriving industry in the collection of beetle specimens for amateur and professional collectors. Many coleopterists prefer to collect beetle specimens for themselves, recording detailed information about each specimen and its habitat. Such collections add to the body of knowledge about the Coleoptera. Some countries have established laws governing or prohibiting the collection of certain rare (and often much sought after) species. One such beetle whose collection is illegal or restricted is the American burying beetle, "Nicrophorus americanus". |