The Calliphoridae are a family of insects in the order Diptera, with 1,200 known species. The maggot larvae used as fishing bait, are known as gentles; the family is known to be polyphyletic, but much remains disputed regarding proper treatment of the constituent taxa, some of which are accorded family status. The name blow fly comes from an older English term for meat that had eggs laid on it, said to be fly blown; the first known association of the term "blow" with flies appears in the plays of William Shakespeare: Love's Labour's Lost, The Tempest, Antony and Cleopatra. Calliphoridae adults are shiny with metallic colouring with blue, green, or black thoraces and abdomens. Antennae are aristate; the arista are plumose the entire length, the second antennal segment is distinctly grooved. Members of Calliphoridae have branched Rs 2 veins, frontal sutures are present, calypters are well developed; the characteristics and arrangement of hairlike bristles are used to tell the difference between members of this family.
All blow flies have bristles located on the meron. Having two notopleural bristles and a hindmost posthumeral bristle located lateral to presutural bristle are characteristics to look for when identifying this family; the thorax has the continuous dorsal suture across the middle, along with well-defined posterior calli. The postscutellum is weakly developed; the costa is unbroken and the subcosta is apparent on the insect. Most species of blow flies studied thus far are anautogenous; the current theory is that females visit carrion both for protein and egg laying, but this remains to be proven. Blow fly eggs yellowish or white in color, are about 1.5 mm x 0.4 mm, when laid, look like rice balls. While the female blow fly lays 150–200 eggs per batch, she is iteroparous, laying around 2,000 eggs during the course of her life; the sex ratio of blow fly eggs is 50:50, but one exception is females from two species of the genus Chrysomya, which are either arrhenogenic or thelygenic. Hatching from an egg to the first larval stage takes about eight hours to one day.
Larvae have three stages of development. The instars are separable by examining openings to the breathing system; the larvae use proteolytic enzymes in their excreta to break down proteins on the livestock or corpse on which they are feeding. Blow flies are poikilothermic – the rate at which they grow and develop is dependent on temperature and species. Under room temperature, the black blow fly Phormia regina can change from egg to pupa in 150–266 hours; when the third larval stage is complete, it will leave the corpse and burrow into the ground to pupate, emerging as an adult seven to fourteen days later. Adult blow flies are occasional pollinators, being attracted to flowers with strong odors resembling rotting meat, such as the American pawpaw or dead horse arum. Little doubt remains that these flies use nectar as a source of carbohydrates to fuel flight, but just how and when this happens is unknown. One study showed the visual stimulus a blow fly receives from its compound eyes is responsible for causing its legs to extend from its flight position and allow it to land on any surface.
Larvae of most species are scavengers of carrion and dung, most constitute the majority of the maggots found in such material, although they are not uncommonly found in close association with other dipterous larvae from the families Sarcophagidae and Muscidae, many other acalyptrate muscoid flies. Predators of blow flies include: spiders, beetles and birds including chickens. About 1,100 species of blow flies are known, with 228 species in the Neotropics, a large number of species in Africa and Southern Europe; the most common areas to find Calliphoridae species are in India, China, Central America, the Southern United States. The typical habitats for blow flies are temperate to tropical areas that provide a layer of loose, damp soil and litter where larvae may thrive and pupate; this is a selected list of genera from the Palearctic, Nearctic and Australasia: Sources: MYIA, FE, Nomina, A/O DC Blow flies have caught the interest of researchers in a variety of fields, although the large body of literature on calliphorids has been concentrated on solving the problem of myiasis in livestock.
The sheep blow fly Lucilia cuprina causes the Australian sheep industry an estimated AU$170 million a year in losses. The most common causes of myiasis in humans and animals are the three dipteran families Oestridae and Sarcophagidae. Myiasis in humans is clinically categorized in six ways: dermal and subdermal, facial cavity, wound or traumatic, gastrointestinal and generalized. If found in humans, the dipteran larvae are in their first instar; the only treatment necessary is just to remove the maggots, the patient heals naturally. Whilst not a myiasis species, the Congo floor maggot feeds on mammal blood human; the New World primary screwworm, once a major pest in southern United States, has been eradicated from the United States and Central America through an extensive release program by the USDA of sterilized males
Pollenia rudis, the common cluster fly, is a species of fly in the family Calliphoridae. Pollenia rudis is known as the attic fly, the loft fly, pollenie du lombric, the buckwheat fly. During the autumn and winter months, Pollenia rudis can be found overwintering inside of attics or lofts; this sluggish species can be found “clustering” near the interior windows of a warm structure. This species is distributed throughout the United States and Europe and is considered a pest species in structures. P. rudis can be found wherever the Allolobophora genera, occurs. These earthworms are located in well-drained, silt-loam soil with grass cover. During the summer, P. rudis can be found in open areas. It is only when there is a sudden drop in temperature that the cluster fly shifts to the interior of structures, holes in trees, loose bark, or other crevices and cavities; the common name "cluster fly" was derived from the clustering behavior in adults of this species in attics and lofts. The common name, "buckwheat fly", is derived from the odor of buckwheat honey the species gives off when they are crushed.
Pollenia rudis was first documented by Johan Christian Fabricius in 1794. At the time, Fabricius listed the species as Musca rudis; this taxonomy was changed in 1830 by André Jean Baptiste Robineau-Desvoidy to Pollenia rudis. The change of genus to Pollenia occurred for Muscids having, among other features, the thorax covered with "down-like clothing". P. rudis has been described under the name of Musca familiaris in 1869 by Dr. T. W. Harris; the cluster fly is a European species and the date of its introduction into the United States is not known. This species gained particular attention in the United States when Dr. W. H. Dall, of the Smithsonian Institution, published an article in the Proceedings of the U. S. National Museum for 1882. Dr. Dall secured specimens of P. rudis for identification. Dr. Dall documented the species appearance in Geneva, NY thirty years prior to his publication. P. rudis may have been introduced to the United States upon slow sailing vessels in the cooler months of the year that traveled from Europe.
This is possible due to the hibernation behaviors of the adult cluster flies to seek shelter for overwintering. The species could have been transported to North America in the ballast of ships containing soil and the cluster fly host, earthworms. All flies can be identified from other species by certain characteristics, they can differ in thoracic coloring, basicosta coloring, spiracle coloring. Size and shape are aids in identification. Pollenia rudis eggs are oblong-shaped, they are small and white. The P. rudis larvae are white with posterior spiracles. The adult Pollenia rudis looks like most of the other Pollenia species such as pallida, dasylpoda, they are dark gray with checkered silvery-black abdomens. A newly emerged fly has many golden hairs on its thorax which may be lost throughout the life of the fly; the stripes on the thorax are not as prominent as on the house fly and the tips of the wings overlap when at rest. The cluster fly is larger than a house fly at 9.525-12.7mm long. The similarities between pallida and rudis are seen in the female specimens.
P. pallida has a flattened facial keel. P.dasyloda has a black head with yellow tint on the frons. The basicosta can be found in many colors ranging from yellow to light brown; some specimens have black basicosta. The posterior spiracle ranges from yellow in color to light brown; the number of bristles and setae found on this species are characteristic of this species only. There are 2-3 rows of setae located on 6-8 strong frontal bristles, they have aristate antennae. The behavior of the P. rudis fly varies with the annual conditions of the day. During the summer, on a sunny day these flies can be found without much trouble; when it is cold these flies tend to find somewhere dry. They are found in forest or wooded areas during the cold season; the flies tend to frequent dry areas because of their aristae antennae. The aristae are sensitive to minute pressure changes. During the winter, adult P. rudis' have a habit of overwintering. This ritual begins; the flies will inhabit the old tunnels created by past insects.
They can be found in old bird nests, under the bark of trees, or in homes. P. rudis will overwinter until spring. Earthworms are a major source of food for Pollenia rudis; the main species of earthworm that these cluster flies infect are Aporrectoda caliginosa, Aporrectoda chlorotica, Eisenia lucens, Lumbricus rubellus, Lumbricus terrestris. After the larvae hatch, they begin looking for worms; the first instar larvae eat their way through the integument section of the earthworm’s epidermis. While feeding, the P. rudis larvae leave the spiracles outside of the earthworm. Inside the earthworm, the larvae feed; the adult P. rudis are, in most cases, herbivores. They feed on many types of organic matter. Plant sap, fruit and feces are common energy pathways for P. rudis. P. rudis is attracted to malt extract, acetyl acetate and the proteins in animal meat. Entomophthora muscae or Entomophthora schizophorae is a fungus that infects adult flies; this fungus causes disease within the fly resulting in a swollen abdomen.
This swollen abdomen makes the wings and legs spread apart causing the fly to have trouble flying. After some time with this disease, a P. rudis adult will lose the ability to fly. Without flight
Insects or Insecta are hexapod invertebrates and the largest group within the arthropod phylum. Definitions and circumscriptions vary; as used here, the term Insecta is synonymous with Ectognatha. Insects have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes and one pair of antennae. Insects are the most diverse group of animals; the total number of extant species is estimated at between ten million. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, which are dominated by another arthropod group, crustaceans. Nearly all insects hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts; the immature stages differ from the adults in structure and habitat, can include a passive pupal stage in those groups that undergo four-stage metamorphosis. Insects that undergo three-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages.
The higher level relationship of the insects is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm; the most diverse insect groups appear to have coevolved with flowering plants. Adult insects move about by walking, flying, or sometimes swimming; 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, composed of the front & rear on one side with the middle on the other side. Insects are the only invertebrates to have evolved flight, all flying insects derive from one common ancestor. Many insects spend at least part of their lives under water, with larval adaptations that include gills, 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 solitary, but some, such as certain bees 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. Lampyrid beetles communicate with light. Humans regard certain insects as pests, attempt to control them using insecticides, a host of other techniques; some insects damage crops by feeding on sap, fruits, or wood. Some species are parasitic, may vector diseases; some insects perform complex ecological roles. Insect pollinators are essential to the life cycle of many flowering plant species on which most organisms, including humans, are at least dependent. Many insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms produce silk and honey bees produce honey and both have been domesticated by humans.
Insects are consumed as food in 80% of the world's nations, by people in 3000 ethnic groups. Human activities have effects on insect biodiversity; the word "insect" comes from the Latin word insectum, meaning "with a notched or divided body", or "cut into", from the neuter singular perfect passive participle of insectare, "to cut into, to cut up", from in- "into" and secare "to cut". A calque of Greek ἔντομον, "cut into sections", Pliny the Elder introduced the Latin designation as a loan-translation of the Greek word ἔντομος or "insect", Aristotle's term for this class of life 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 form the usual word for "insect" in Welsh, Serbo-Croatian, etc; the precise definition of the taxon Insecta and the equivalent English name "insect" varies. In the broadest circumscription, Insecta sensu lato consists of all hexapods. Traditionally, insects defined in this way were divided into "Apterygota" —the wingless insects—and Pterygota—the winged insects.
However, modern phylogenetic studies have shown that "Apterygota" is not monophyletic, so does not form a good taxon. A narrower circumscription restricts insects to those hexapods with external mouthparts, comprises only the last three groups in the table. In this sense, Insecta sensu stricto is equivalent to Ectognatha. In the narrowest circumscription, insects are restricted to hexapods that are either winged or descended from winged ancestors. Insecta sensu strictissimo is equivalent to Pterygota. For the purposes of this article, the middle definition is used; the evolutionary relationship of insects to other animal groups remains unclear. Although traditionally grouped with millipedes and centiped
Justin Pierre Marie Macquart
Pierre-Justin-Marie Macquart was a French entomologist specialising in the study of Diptera. He described many new species. Macquart was born in Hazebrouck, France in 1776 and died in Lille in 1855, he was interested in natural history from an early age due to his older brother, an ornithologist and a Fellow of the Société de Sciences de l’Agriculture et des Arts de la Ville de Lille and whose bird collection became the foundation of the societies museum, the Musée d'Histoire Naturelle de Lille. A second brother founded a botanic garden with a collection of over 3000 species of plants. Macquart, too became interested in natural history. In 1796 he joined the staff of General Armand Samuel campaigning in the Revolutionary Wars, he was a draftsman. The general staff was stationed in Schwetzingen Heidelberg, Aarau and Zurich, he left the army in 1798 returning to Lille with German books and birds. He worked full-time on insects and studying in the library and on 27 Nivôse, Year 11 of the French Revolutionary Calendar he was elected a Fellow of the Société de Sciences de l’Agriculture et des Arts de la Ville de Lille.
Soon he began travelling around France and went several times to Paris where he met Pierre André Latreille who suggested to specialize on Diptera, following the pioneering work of Johann Wilhelm Meigen. After some time in Holland he married and moved from Hazebrouck to Lestrem where he became a Conseillers régionaux of the Conseil régional du Nord-Pas-de-Calais. At this time he began intensive studies of Diptera examining the collections of Henri Marie Ducrotay de Blainville, Étienne Geoffroy Saint-Hilaire, André Étienne d'Audebert de Férussac, Amédée Louis Michel Lepeletier de Saint Fargeau, Jean Guillaume Audinet-Serville, Alexandre Louis Lefèbvre de Cérisy, Gaspard Auguste Brullé and François Louis de la Porte, comte de Castelnau in France, he went to Hamburg where Wilhelm von Winthem had assembled the largest collection of Diptera in the world. At the age of 25 he was one of the founders of the Société d’Amateurs des Sciences et Arts de la Ville de Lille. Many of his publications were published in the Mémoires of this Society.
He expanded the natural history holdings of the Musee d'Histoire Naturelle de Lille. His early taxonomic work included the Insectes diptères du nord de la France, published in Lille in 4 parts from 1826-1829; this prompted Latreille to enlist him as the author of the Diptera volumes of Suites à Buffon under his editorship. This arrangement was continued by Nicolas Roret. Two volumes were published as Histoire naturelle des insectes Dipteres where non-European as well as European Diptera were treated. In 1839 Macquart visited Johann Wilhelm Meigen aged 75, in Stolberg, purchasing his notes and drawings and bringing his collection to Paris where it is now in the Muséum national d'histoire naturelle; this established Macquart as Paris as the centre of Dipterology. The only works on exotic Diptera at this time were those of Christian Rudolph Wilhelm Wiedemann Diptera exotica and Aussereuropaischen Diptera. Wiedemann had not seen the imposing collections in Paris and these were to occupy Macquart for the rest of his life.
He described nearly 2,000 new species in his Insectes diptères exotiques nouveaux ou peu connus which lists the collections examined to that date. They are those of: Jules Dumont d'Urville with René-Primevère Lesson. S. A. but lived for five years in Yucatán. Material continued to pour into the museum from these and other sources as Macquarts reputation spread. In 1845 Macquart went to Switzerland to see Maximilian Perty and from there to Germany, aware that events were moving to the revolutions of 1848; this was his last journey outside Paris. He is buried in Lille. Macquart was a Member of the Entomological Society of Stettin, the Linnean Society of London and the Société entomologique de France 1811. Mémoire sur les plantations dans le département du Nord. Séance Publique de la Société des Sciences de Lille, 4, 116–131. 1819. Notice sur les insectes Hemiptères du genre Psylle. Seanc Soc Sci Agr Arts Lille 5: 81-86. 1826 Insectes diptères du nord de la France 1 and 2 Asiliques, xylotomes, leptides, vésiculeux, xylophagites, tabaniens Lille: impr.
L. Danel. 1827 Insectes diptères du nord de la France 3 Platypézines, empides, hybotides Lille: impr. L. Danel. 1829 Insectes diptères du nord de la France 4, Syrphies Lille: impr. L. Danel. 1834-1835. Histoire naturelle des insectes. Dipteres Paris: Roret. 1838 Insectes diptères exotiques nouveaux ou peu connus. Two volumes. Paris: Roret. All
In zoological nomenclature, a type species is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e. the species that contains the biological type specimen. A similar concept is used for suprageneric groups called a type genus. In botanical nomenclature, these terms have no formal standing under the code of nomenclature, but are sometimes borrowed from zoological nomenclature. In botany, the type of a genus name is a specimen, the type of a species name; the species name that has that type can be referred to as the type of the genus name. Names of genus and family ranks, the various subdivisions of those ranks, some higher-rank names based on genus names, have such types. In bacteriology, a type species is assigned for each genus; every named genus or subgenus in zoology, whether or not recognized as valid, is theoretically associated with a type species. In practice, there is a backlog of untypified names defined in older publications when it was not required to specify a type.
A type species is both a concept and a practical system, used in the classification and nomenclature of animals. The "type species" represents the reference species and thus "definition" for a particular genus name. Whenever a taxon containing multiple species must be divided into more than one genus, the type species automatically assigns the name of the original taxon to one of the resulting new taxa, the one that includes the type species; the term "type species" is regulated in zoological nomenclature by article 42.3 of the International Code of Zoological Nomenclature, which defines a type species as the name-bearing type of the name of a genus or subgenus. In the Glossary, type species is defined as The nominal species, the name-bearing type of a nominal genus or subgenus; the type species permanently attaches a formal name to a genus by providing just one species within that genus to which the genus name is permanently linked. The species name in turn is fixed, to a type specimen. For example, the type species for the land snail genus Monacha is Helix cartusiana, the name under which the species was first described, known as Monacha cartusiana when placed in the genus Monacha.
That genus is placed within the family Hygromiidae. The type genus for that family is the genus Hygromia; the concept of the type species in zoology was introduced by Pierre André Latreille. The International Code of Zoological Nomenclature states that the original name of the type species should always be cited, it gives an example in Article 67.1. Astacus marinus Fabricius, 1775 was designated as the type species of the genus Homarus, thus giving it the name Homarus marinus. However, the type species of Homarus should always be cited using its original name, i.e. Astacus marinus Fabricius, 1775. Although the International Code of Nomenclature for algae and plants does not contain the same explicit statement, examples make it clear that the original name is used, so that the "type species" of a genus name need not have a name within that genus, thus in Article 10, Ex. 3, the type of the genus name Elodes is quoted as the type of the species name Hypericum aegypticum, not as the type of the species name Elodes aegyptica.
Glossary of scientific naming Genetypes – genetic sequence data from type specimens. Holotype Paratype Principle of Typification Type Type genus
The abdomen constitutes the part of the body between the thorax and pelvis, in humans and in other vertebrates. The abdomen is the frontal part of the abdominal segment of the trunk, the dorsal part of this segment being the back of the abdomen; the region occupied by the abdomen is termed the abdominal cavity. In arthropods it is the posterior tagma of the body; the abdomen stretches from the thorax at the thoracic diaphragm to the pelvis at the pelvic brim. The pelvic brim stretches from the lumbosacral joint to the pubic symphysis and is the edge of the pelvic inlet; the space above this inlet and under the thoracic diaphragm is termed the abdominal cavity. The boundary of the abdominal cavity is the abdominal wall in the front and the peritoneal surface at the rear; the abdomen contains most of the tubelike organs of the digestive tract, as well as several solid organs. Hollow abdominal organs include the stomach, the small intestine, the colon with its attached appendix. Organs such as the liver, its attached gallbladder, the pancreas function in close association with the digestive tract and communicate with it via ducts.
The spleen and adrenal glands lie within the abdomen, along with many blood vessels including the aorta and inferior vena cava. Anatomists may consider the urinary bladder, fallopian tubes, ovaries as either abdominal organs or as pelvic organs; the abdomen contains an extensive membrane called the peritoneum. A fold of peritoneum may cover certain organs, whereas it may cover only one side of organs that lie closer to the abdominal wall. Anatomists call the latter type of organs retroperitoneal. Digestive tract: Stomach, small intestine, large intestine with cecum and appendix Accessory organs of the digestive tract: Liver and pancreas Urinary system: Kidneys and ureters – but technically located in retroperitoneum – outside peritoneal membrane Other organs: SpleenAbdominal organs can be specialized in some animals. For example, the stomach of ruminants is divided into four chambers – rumen, reticulum and abomasum. In vertebrates, the abdomen is a large cavity enclosed by the abdominal muscles and laterally, by the vertebral column dorsally.
Lower ribs can enclose ventral and lateral walls. The abdominal cavity is upper part of the pelvic cavity, it is attached to the thoracic cavity by the diaphragm. Structures such as the aorta, inferior vena cava and esophagus pass through the diaphragm. Both the abdominal and pelvic cavities are lined by a serous membrane known as the parietal peritoneum; this membrane is continuous with the visceral peritoneum lining the organs. The abdomen in vertebrates contains a number of organs belonging, for instance, to the digestive tract and urinary system. There are three layers of the abdominal wall, they are, from the outside to the inside: external oblique, internal oblique, transverse abdominal. The first three layers extend between the vertebral column, the lower ribs, the iliac crest and pubis of the hip. All of their fibers merge towards the midline and surround the rectus abdominis in a sheath before joining up on the opposite side at the linea alba. Strength is gained by the criss-crossing of fibers, such that the external oblique are downward and forward, the internal oblique upward and forward, the transverse abdominal horizontally forward.
The transverse abdominal muscle is triangular, with its fibers running horizontally. It lies between the underlying transverse fascia, it originates from Poupart's ligament, the inner lip of the ilium, the lumbar fascia and the inner surface of the cartilages of the six lower ribs. It inserts into the linea alba behind the rectus abdominis; the rectus abdominis muscles are flat. The muscle is crossed by three fibrous bands called the tendinous intersections; the rectus abdominis is enclosed in a thick sheath formed, as described above, by fibers from each of the three muscles of the lateral abdominal wall. They originate at the pubis bone, run up the abdomen on either side of the linea alba, insert into the cartilages of the fifth and seventh ribs. In the region of the groin, the inguinal canal, a passage through the layers; this gap is where the testes can drop through the wall and where the fibrous cord from the uterus in the female runs. This is where weakness can form, cause inguinal hernias.
The pyramidalis muscle is triangular. It is located in the lower abdomen in front of the rectus abdominis, it is inserted into the linea alba halfway up to the navel. Functionally, the human abdomen is where most of the alimentary tract is placed and so most of the absorption and digestion of food occurs here; the alimentary tract in the abdomen consists of the lower esophagus, the stomach, the duodenum, the jejunum, the cecum and the appendix, the ascending and descending colons, the sigmoid colon and the rectum. Other vital organs inside the abdomen include the kidneys, the pancreas and the spleen; the abdominal wall is split into the posterior and anterior walls. The abdominal muscles have different important functions, they assist in the breathing process as accessory muscles of respiration. Moreover, these muscles serve as protection for the inner organs. Furthermore, together with the back muscles they provide postural support and are important in defining the form; when the glottis is closed and the thorax and pelvis are fixed, they are integral in the cough, defecation, childbirth and singing functions.
Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy characterized by low body temperature, slow breathing and heart rate, low metabolic rate, it is most observed during the winter months. Although traditionally reserved for "deep" hibernators such as rodents, the term has been redefined to include animals such as bears and is now applied based on active metabolic suppression rather than any absolute decline in body temperature. Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms; the equivalent during the summer months is aestivation. Associated with low temperatures, hibernation functions to conserve energy when sufficient food is unavailable. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature. Hibernation may last days, weeks, or months depending on the species, ambient temperature, time of year, the individual's body condition.
Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period as long as the entire winter. Larger species become hyperphagic, eating a large amount of food and storing the energy in fat deposits. In many small species, food caching replaces becoming fat; some species of mammals hibernate while gestating young, which are born either while the mother hibernates or shortly afterwards. For example, female polar bears go into hibernation during the cold winter months in order to give birth to their offspring; the pregnant mothers increase their body mass prior to hibernation, this increase is further reflected in the weight of the offspring. The fat accumulation enables them to provide a sufficiently warm and nurturing environment for their newborns. During hibernation, they subsequently lose 15–27% of their pre-hibernation weight by using their stored fats for energy. True hibernation is restricted to endotherms. Still, many ectothermic animals undergo periods of dormancy which are sometimes confused with hibernation.
Some reptile species are said to brumate, but possible similarities between brumation and hibernation are not established. Many insects, such as the wasp Polistes exclamans, exhibit periods of dormancy which have been referred to as hibernation, despite their ectothermy. Obligate hibernators are animals that spontaneously, annually, enter hibernation regardless of ambient temperature and access to food. Obligate hibernators include many species of ground squirrels, other rodents, mouse lemurs, European hedgehogs and other insectivores and marsupials These species undergo what has been traditionally called "hibernation": a physiological state wherein the body temperature drops to near ambient temperature, heart and respiration rates slow drastically; the typical winter season for obligate hibernators is characterized by periods of torpor interrupted by periodic, euthermic arousals, during which body temperatures and heart rates are restored to more typical levels. The cause and purpose of these arousals is still not clear.
One favored hypothesis is that hibernators build a "sleep debt" during hibernation, so must warm up to sleep. This has been supported by evidence in the Arctic ground squirrel. Other theories postulate that brief periods of high body temperature during hibernation allow the animal to restore its available energy sources or to initiate an immune response. Hibernating Arctic ground squirrels may exhibit abdominal temperatures as low as −2.9 °C, maintaining sub-zero abdominal temperatures for more than three weeks at a time, although the temperatures at the head and neck remain at 0 °C or above. There was a question of whether or not bears hibernate since they experience only a modest decline in body temperature compared with the much larger decreases seen in other hibernators. Many researchers thought that their deep sleep was not comparable with true, deep hibernation, but recent research has refuted this theory in captive black bears. Unlike obligate hibernators, facultative hibernators only enter hibernation when either cold-stressed, food-deprived, or both.
A good example of the differences between these two types of hibernation can be seen in prairie dogs: the white-tailed prairie dog is an obligate hibernator and the related black-tailed prairie dog is a facultative hibernator. While hibernation has long been studied in rodents, namely ground squirrels, no primate or tropical mammal was known to hibernate until the discovery of hibernation in the fat-tailed dwarf lemur of Madagascar, which hibernates in tree holes for seven months of the year. Malagasy winter temperatures sometimes rise to over 30 °C, so hibernation is not an adaptation to low ambient temperatures; the hibernation of this lemur is dependent on the thermal behaviour of its tree hole: if the hole is poorly insulated, the lemur's body temperature fluctuates passively following the ambient temperature. Dausmann found that hypometabolism in hibernating animals is not coupled with low body temperature. Hibernating bears are able to recycle their proteins and urine, allowing them both to stop urinating for months and to avoid muscl