In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer layer or covering), either at specific times of the year, or at specific points in its life cycle.
Moulting can involve shedding the epidermis (skin), pelage (hair, feathers, fur, wool), or other external layer. In some groups, other body parts may be shed, for example, wings in some insects or the entire exoskeleton in arthropods.
|Cats||Fur||Usually around spring-summer time||Cats moult fur around spring-summer time to get rid of their "winter coat". Cats have thicker fur during the colder winter months to keep them warm, then around spring and summer they shed some of their fur to get a thinner coat for the warmer summer months. Some cats need brushing during moulting, since dead hairs can get trapped in the cat's fur.|
|Chickens||Feathers||Usually autumn (non-commercial hens).||Chickens generally stop laying eggs when their moulting begins and recommence laying when their new feathers have re-grown.|
|Dogs and other canids||Fur||Semi-annually, spring and fall (autumn).||Moulting or shedding in canids, as in all mammals, is due to fluctuations in the amount of melatonin secreted by their pineal gland in response to seasonal sunlight variations rather than temperature variations. This seasonality in moulting is most preserved in Arctic breeds of dogs which shed twice each year whereas most other breeds moult once each year.|
|Snakes||Skin||Regularly, when old skin is outgrown.||Snakes rub against rough surfaces to assist removal of their shed skin.|
|Lizards||Skin||Regularly, when old skin is outgrown.||Lizards, like snakes, rub against objects to help remove their shed skin and then consume the shed skin for calcium and other nutrients.|
|Hermit crabs||Exoskeleton||Regularly, when the carapace is outgrown.||Land hermit crabs bury themselves for many weeks while they moult and then consume their exoskeleton.|
|Amphibians||Skin||Regularly.||Salamanders and frogs shed their skins regularly, then often eat it.|
|Arachnids||Exoskeleton||Regularly, when the exoskeleton is outgrown.||Arachnids moult regularly to grow, often becoming reclusive and fasting for long periods prior to a moult.|
|Insects||Exoskeleton||Regularly in larvae, when the exoskeleton is outgrown.||In species with "complete" metamorphosis, the final moult transforms the body, typically from a soft-bodied larva to a reproductive, winged and sometimes colourful adult. In mayflies, a winged subimago moults one last time to a winged adult.|
|A loggerhead shrike in mid-moult (left) and with regular plumage (right).|
In birds, moulting is the periodic replacement of feathers by shedding old feathers while producing new ones. Feathers are dead structures at maturity which are gradually abraded and need to be replaced. Adult birds moult at least once a year, although many moult twice and a few three times each year. It is generally a slow process as birds rarely shed all their feathers at any one time; the bird must retain sufficient feathers to regulate its body temperature and repel moisture. The number and area of feathers that are shed varies. In some moulting periods, a bird may renew only the feathers on the head and body, shedding the wing and tail feathers during a later moulting period. Some species of bird become flightless during an annual "wing moult" and must seek a protected habitat with a reliable food supply during that time. While the plumage may appear thin or uneven during the moult, the bird's general shape is maintained despite the loss of apparently many feathers; bald spots are typically signs of unrelated illnesses, such as gross injuries, parasites, feather pecking (especially in commercial poultry), or (in pet birds) feather plucking. Some birds will drop feathers, especially tail feathers, in what is called a "fright moult".
The process of moulting in birds is as follows: First, the bird begins to shed some old feathers, then pin feathers grow in to replace the old feathers. As the pin feathers become full feathers, other feathers are shed. This is a cyclical process that occurs in many phases. It is usually symmetrical, with feather loss equal on each side of the body. Because feathers make up 4–12% of a bird's body weight, it takes a large amount of energy to replace them. For this reason, moults often occur immediately after the breeding season, but while food is still abundant. The plumage produced during this time is called postnuptial plumage. Prenuptial moulting occurs in red-collared widowbirds where the males replace their nonbreeding plumage with breeding plumage. It is thought that large birds can advance the moult of severely damaged feathers.
Determining the process birds go through during moult can be useful in understanding breeding, migration and foraging strategies.  One non-invasive method of studying moult in birds is through using field photography.  The evolutionary and ecological forces driving moult can also be investigated using intrinsic markers such as stable hydrogen isotope (δ2H) analysis. 
In some countries, flocks of commercial layer hens are force-moulted to reinvigorate egg-laying. This usually involves complete withdrawal of their food and sometimes water for 7–14 days or up to 28 days under experimental conditions, which presumably reflect standard farming practice in some countries. This causes a body weight loss of 25 to 35%, which stimulates the hen to lose her feathers, but also reinvigorates egg-production. Some flocks may be force-moulted several times. In 2003, more than 75% of all flocks were force-moulted in the US. Other methods of inducing a moult include low-density diets (e.g. grape pomace, cotton seed meal, alfalfa meal) or dietary manipulation to create an imbalance of a particular nutrient(s). The most important among these include manipulation of minerals including sodium (Na), calcium (Ca), iodine (I) and zinc (Zn), with full or partially reduced dietary intakes.
The most familiar example of moulting in reptiles is when snakes "shed their skin". This is usually achieved by the snake rubbing its head against a hard object, such as a rock (or between two rocks) or piece of wood, causing the already stretched skin to split. At this point, the snake continues to rub its skin on objects, causing the end nearest the head to peel back on itself, until the snake is able to crawl out of its skin, effectively turning the moulted skin inside-out. This is similar to how one might remove a sock from one's foot by grabbing the open end and pulling it over itself. The snake's skin is often left in one piece after the moulting process, including the discarded brille (ocular scale), so that the moult is vital for maintaining the animal's quality of vision. The skins of lizards, in contrast, generally fall off in pieces.
In arthropods, such as insects, arachnids and crustaceans, moulting is the shedding of the exoskeleton (which is often called its shell), typically to let the organism grow. This process is called ecdysis. It is commonly said that ecdysis is necessary because the exoskeleton is rigid and cannot grow like skin, but this is simplistic, ignoring the fact that most Arthropoda with soft, flexible skins also undergo ecdysis. Among other things, ecdysis permits metamorphosis, the sometimes radical difference between the morphology of successive instars, and the fact that a new skin can replace structures, such as by providing new external lenses for eyes. The new exoskeleton is initially soft but hardens after the moulting of the old exoskeleton. The old exoskeleton is called an exuviae. While moulting, insects can't breathe.
An arthropod (, from Greek ἄρθρον arthron, "joint" and πούς pous, "foot") is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans. The term Arthropoda as originally proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora.
Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthopods are bilaterally symmetrical and their body possesses an external skeleton. Some species have wings.
Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments. They have over a million described species, making up more than 80 percent of all described living animal species, some of which, unlike most other animals, are very successful in dry environments. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab.
Arthropods' primary internal cavity is a haemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates; they have open circulatory systems. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong. Their vision relies on various combinations of compound eyes and pigment-pit ocelli: in most species the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information, but the main eyes of spiders are ocelli that can form images and, in a few cases, can swivel to track prey. Arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many bristles known as setae that project through their cuticles. Arthropods' methods of reproduction and development are diverse; all terrestrial species use internal fertilization, but this is often by indirect transfer of the sperm via an appendage or the ground, rather than by direct injection.
The evolutionary ancestry of arthropods dates back to the Cambrian period. The group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians (or their constituent clades) in a superphylum Ecdysozoa. Overall, however, the basal relationships of animals are not yet well resolved. Likewise, the relationships between various arthropod groups are still actively debated. Aquatic species use either internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother. Arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of maternal care for hatchlings varies from nonexistent to the prolonged care provided by scorpions.
Arthropods contribute to the human food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread severe disease to humans, livestock, and crops.Arthropod cuticle
The cuticle forms the major part of the integument of the Arthropoda. It includes most of the material of the exoskeleton of the insects, Crustacea, Arachnida, and Myriapoda.Crustacean neurohormone family
In molecular biology, the crustacean neurohormone family of proteins is a family of neuropeptides expressed by arthropods. The family includes the following types of neurohormones:
Crustacean hyperglycaemic hormone (CHH). CHH is primarily involved in blood sugar regulation, but also plays a role in the control of moulting and reproduction.
Moult-inhibiting hormone (MIH). MIH inhibits Y-organs where moulting hormone (ecdysteroid) is secreted. A moulting cycle is initiated when MIH secretion diminishes or stops.
Gonad-inhibiting hormone (GIH), also known as vitellogenesis-inhibiting hormone (VIH) because of its role in inhibiting vitellogenesis in female animals.
Mandibular organ-inhibiting hormone (MOIH). MOIH represses the synthesis of methyl farnesoate, the precursor of insect juvenile hormone III in the mandibular organ.
Ion transport peptide (ITP) from locust. ITP stimulates salt and water reabsorption and inhibits acid secretion in the ileum of the locust.
Caenorhabditis elegans uncharacterised protein ZC168.2.These neurohormones are peptides of 70 to 80 amino acid residues which are processed from larger precursors. They contain six conserved cysteines that are involved in disulfide bonds.Ecdysis
Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remnants of the old, empty exoskeleton are called exuviae.After moulting, an arthropod is described as teneral, a callow; it is "fresh", pale and soft-bodied. Within one or two hours, the cuticle hardens and darkens following a tanning process analogous to the production of leather. During this short phase the animal expands, since growth is otherwise constrained by the rigidity of the exoskeleton. Growth of the limbs and other parts normally covered by hard exoskeleton is achieved by transfer of body fluids from soft parts before the new skin hardens. A spider with a small abdomen may be undernourished but more probably has recently undergone ecdysis. Some arthropods, especially large insects with tracheal respiration, expand their new exoskeleton by swallowing or otherwise taking in air. The maturation of the structure and colouration of the new exoskeleton might take days or weeks in a long-lived insect; this can make it difficult to identify an individual if it has recently undergone ecdysis.
Ecdysis allows damaged tissue and missing limbs to be regenerated or substantially re-formed. Complete regeneration may require a series of moults, the stump becoming a little larger with each moult until it is a normal, or near normal, size.Ecdysone
Ecdysone is a steroidal prohormone of the major insect molting hormone 20-hydroxyecdysone, which is secreted from the prothoracic glands. Insect molting hormones (ecdysone and its homologues) are generally called ecdysteroids. Ecdysteroids act as moulting hormones of arthropods but also occur in other related phyla where they can play different roles. In Drosophila melanogaster, an increase in ecdysone concentration induces the expression of genes coding for proteins that the larva requires, and it causes chromosome puffs (sites of high expression) to form in polytene chromosomes. Recent findings in the laboratory of Chris Q. Doe have found a novel role of this hormone in regulating temporal gene transitions within neural stem cells of the fruit fly. Ecdysone and other ecdysteroids also appear in many plants mostly as a protection agent (toxins or antifeedants) against herbivorous insects.These phytoecdysteroids have been reputed to have medicinal value and are part of herbal adaptogenic remedies like Cordyceps, yet an ecdysteroid precursor in plants has been shown to have cytotoxic properties.Tebufenozide, sold under the Bayer trademark MIMIC, has ecdysteroid activity although its chemical structure has little resemblance to the ecdysteroids.Ecdysozoa
Ecdysozoa () is a group of protostome animals, including Arthropoda (insects, chelicerata, crustaceans, and myriapods), Nematoda, and several smaller phyla. They were first defined by Aguinaldo et al. in 1997, based mainly on phylogenetic trees constructed using 18S ribosomal RNA genes. A large study in 2008 by Dunn et al. strongly supported the Ecdysozoa as a clade, that is, a group consisting of a common ancestor and all its descendants.The group is also supported by morphological characters, and includes all animals that grow by ecdysis, moulting their exoskeleton.
The group was initially contested by a significant minority of biologists. Some argued for groupings based on more traditional taxonomic techniques, while others contested the interpretation of the molecular data.Exopterygota
The Exopterygota, also known as Hemipterodea, are a superorder of insects of the subclass Pterygota in the infraclass Neoptera, in which the young resemble adults but have externally developing wings. They undergo a modest change between immature and adult, without going through a pupal stage. The nymphs develop gradually into adults through a process of moulting.
The Exopterygota are a highly diverse insect superorder, with at least 130,000 living species divided between 15 orders. They include cockroaches, termites, grasshoppers, thrips, lice and stick insects, among many other types of insects.
They are distinguished from the Endopterygota (or Holometabola) by the way in which their wings develop. Endopterygota (meaning literally "internal winged forms") develop wings inside the body and undergo an elaborate metamorphosis involving a pupal stage. Exopterygota ("external winged forms") develop wings on the outside of their bodies without going through a true pupal stage, though a few have something resembling a pupa (e.g., Aleyrodidae).
Ephemeroptera (mayflies) and Odonata (dragonflies and damselflies) also have gradual wing development, this being a plesiomorphic trait. These two orders belong to the infraclass Palaeoptera however, which is not included in Neoptera. As opposed to Neoptera, they cannot fold their wings over their back in the horizontal plane, only vertically (as damselflies do) if at all.Forced molting
Forced molting, sometimes known as induced molting, is the practice by some poultry industries of artificially provoking a flock to molt simultaneously, typically by withdrawing food for 7–14 days and sometimes also withdrawing water for an extended period. Forced molting is usually implemented when egg-production is naturally decreasing toward the end of the first egg-laying phase. During the forced molt, the birds cease producing eggs for at least two weeks, which allows the bird's reproductive tracts to regress and rejuvenate. After the molt, the hen's egg production rate usually peaks slightly lower than the previous peak, but egg quality is improved. The purpose of forced molting is therefore to increase egg production, egg quality, and profitability of flocks in their second or subsequent laying phases, by not allowing the hen's body the necessary time to rejuvenate during the natural cycle of feather replenishment.
The practice is controversial. While it is widespread in the US, it is prohibited in the EU.Great Oyster Bay
Great Oyster Bay is a broad and sheltered bay on the east coast of Tasmania, Australia which opens onto the Tasman Sea. The Tasman Highway runs close to the West Coast of the bay with views of the granite peaks of the Hazards and Schouten Island of the Freycinet Peninsula which are incorporated in the Freycinet National Park.
Towns on the bay include Swansea and Coles Bay.
At the north of the bay the floodplains of the Aspley and Swan rivers has created Moulting Lagoon, an important Ramsar-listed wetland, much of which lies in the Moulting Lagoon Game Reserve. Nearby is the Friendly Beaches Reserve owned and managed by Bush Heritage Australia (BHA).Großer Knechtsand
The Großer Knechtsand is a large sandbank beyond the Weser and Elbe estuaries (in the Elbe-Weser Triangle) in the eastern part of Lower Saxony's Wadden Sea off the coast of North Germany. It lies between the islands of Mellum (which is 16 km (9.9 mi) to the southwest) and Neuwerk (11 km [6.8 mi] northeast). The central area of the sandbank lies above the high water mark, forming the Hochsand of Hoher Knechtsand, which was formerly an island. The Hochsand lies 11 km west of the village of Berensch on the nearest part of the mainland in the borough of Cuxhaven in the Land Wursten.
The Hoher Knechtsand measures 2.5 km (1.6 mi) in an east-west direction and is between 0.6 km (0.37 mi) wide in the west and 1.6 km (0.99 mi) wide in the east. The area of the sandbank above the high water mark is about 2.6 km2 (1.0 sq mi).
The Großer Knechtsand, together with the island of Trischen, is one of the most important moulting areas for the shelduck, and, with Trischen, Norderoog and Minsener Oog, has one of the largest and longest-lasting colonies of Sandwich terns. Eider duck and common seal also occur here in large numbers.
East of the Großer Knechtsand lie the mudflats of Spiekaer Barre. To the north and south it is bordered by the tidal channels (Priele) of Westertill, Ostertill and Robins Balje. Further southeast is the Wurster Watt off the coast of Land Wursten.
To enable the population of Heligoland to return to their home, the then Chancellor, Konrad Adenauer, offered the area around the Großer Knechtsand as an alternative site for military exercises. As a result, from 1952 the area acted as a target for practice bombing sharp explosive and incendiary bombs of the British Royal Air Force instead of Heligoland. A few years later, environmental awareness had increased and, when the contract expired in 1957, it was not renewed. This important area for resting and moulting shelduck and other seabirds was designated in 1957 as the largest German nature reserve in Germany. Since 1986 the area has been part of the strictly protected 'quiet zone' of Lower Saxon Wadden Sea National Park.
About 2 km northwest of the Großer Knechtsand lies the sandbanks of Kleine Knechtsände (53°50′N 8°18′E).Hauling-out
Hauling-out is a behaviour associated with pinnipeds (true seals, sea lions, fur seals and walruses) temporarily leaving the water. Hauling-out typically occurs between periods of foraging activity. Rather than remain in the water, pinnipeds haul-out onto land or sea-ice for reasons such as reproduction and rest. Hauling-out is necessary in seals for mating (with the exception of the Baikal seal) and giving birth (although a distinction is generally made between reproductive aggregations, termed "rookeries", and non-reproductive aggregations, termed "haul-outs"). Other benefits of hauling-out may include predator avoidance, thermoregulation, social activity, parasite reduction and rest.There is much variation in haul-out patterns among different seal species. Haul-out sites may be segregated by age and sex within the same species. Many species of pinniped have only a few localized rookeries where they breed, but periodically occupy hundreds of haul-out sites throughout the range. For example, the Australian fur seals breed on only nine islands in Bass Strait but also occupy up to 50 haul-out sites in south-east Australian waters, and Steller sea lions have around 50 rookeries throughout their range, but several hundred haul-out sites.
Hauling-out behaviour provides numerous benefits to pinnipeds besides reproduction. This behaviour has been shown to be used for activities such as thermoregulation, predator avoidance, moulting, nursing, and resting. Haul-out frequency, duration, and site location (ie. sea-ice, floating-ice, and terrestrial) are all influenced by physical constraints (ie. air temperature, wind speed, and time of day) and biological constraints (ie. moulting, age, and sex). Variations in hauling-out behaviour exist among pinnipeds for reasons such as geographical location.Husk
Husk (or hull) in botany is the outer shell or coating of a seed. It often refers to the leafy outer covering of an ear of maize (corn) as it grows on the plant. Literally, a husk or hull includes the protective outer covering of a seed, fruit, or vegetable. It can also refer to the exuvia of bugs or small animals left behind after moulting.
In cooking, hull can also refer to other waste parts of fruits and vegetables, notably the cap or sepal of a strawberry.
The husk of a legume and some similar fruits is called a pod.
Plantago-seed mucilage is often referred to as husk, or psyllium husk.
Crop plants of several species have been selected that have hulless seeds, including pumpkins, oats, and barley.Insect physiology
Insect physiology includes the physiology and biochemistry of insect organ systems.Although diverse, insects are quite similar in overall design, internally and externally. The insect is made up of three main body regions (tagmata), the head, thorax and abdomen.
The head comprises six fused segments with compound eyes, ocelli, antennae and mouthparts, which differ according to the insect's particular diet, e.g. grinding, sucking, lapping and chewing. The thorax is made up of three segments: the pro, meso and meta thorax, each supporting a pair of legs which may also differ, depending on function, e.g. jumping, digging, swimming and running. Usually the middle and the last segment of the thorax have paired wings. The abdomen generally comprises eleven segments and contains the digestive and reproductive organs.
A general overview of the internal structure and physiology of the insect is presented, including digestive, circulatory, respiratory, muscular, endocrine and nervous systems, as well as sensory organs, temperature control, flight and molting.Instar
An instar ( (listen), from the Latin "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (ecdysis), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i.e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they either pupate or moult again. The instar period of growth is fixed; however, in some insects, like the salvinia stem-borer moth, the number of instars depends on early larval nutrition. Some arthropods can continue to moult after sexual maturity, but the stages between these subsequent moults are generally not called instars.
For most insect species, an instar is the developmental stage of the larval forms of holometabolous (complete metamorphism) or nymphal forms of hemimetabolous (incomplete metamorphism) insects, but an instar can be any developmental stage including pupa or imago (the adult, which does not moult in insects).
The number of instars an insect undergoes often depends on the species and the environmental conditions, as described for a number of species of Lepidoptera. However it is believed that the number of instars can be physiologically constant per species in some insect orders, as for example Diptera and Hymenoptera. It should be minded that the number of larval instars is not directly related to speed of development. For instance, environmental conditions may dramatically affect the developmental rates of species and still have no impact on the number of larval instars. As examples, lower temperatures and lower humidity often slow the rate of development- an example is seen in the lepidopteran tobacco budworm and that may have an effect on how many molts will caterpillars undergo. On the other hand, temperature is demonstrated to affect the development rates of a number of hymenopterans without affecting numbers of instars or larval morphology, as observed in the ensign wasp and in the red imported fire ant. In fact the number of larval instars in ants has been the subject of a number of recent investigations, and no instances of temperature-related variation in numbers of instars have yet been recorded.Moulting Lagoon Important Bird Area
Moulting Lagoon Important Bird Area is a composite wetland site in eastern Tasmania, Australia. It comprises two adjacent and hydrologically continuous wetlands – Moulting Lagoon and the Apsley Marshes – at the head of Great Oyster Bay, near the base of the Freycinet Peninsula, between the towns of Swansea and Bicheno. Both components of the site are listed separately under the Ramsar Convention as wetlands of international significance. Moulting Lagoon is so named because it is a traditional moulting place for black swans. It is an important site for waterbirds.Mue
Mue (French "the moulting") is Émilie Simon's sixth studio album, released by Barclay Records on 17 March 2014.Pin feather
A pin feather, sometimes called a "blood feather", is a developing feather on a bird. This feather can grow as a new feather during the bird's infancy, or grow to replace one from moulting.
The pin feather looks somewhat like a feather shaft. However, unlike a fully developed feather, the pin feather has a blood supply flowing through it. As such, if the pin feather is damaged, a bird can bleed heavily.
As the pin feather grows longer, the blood supply is concentrated in only the base of the shaft, and the tip of the shaft encases the feather itself, in a waxy coating. As moulting birds preen, they remove the waxy coating, and the feather unfurls.
When the blood has receded, the term "blood feather" is no longer synonymous with "pin feather" – it can only be referred to as a pin feather.Ptychopariida
Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian extinction event.
Trilobites have facial sutures that run along the margin of the glabella and/or fixigena to the shoulder point where the cephalon meets the thorax. These sutures outline the cranidium, or the main, central part of the head that does not include the librigena (free cheeks). The eyes are medial along the glabella on the suture line (and some species have no eyes). The fossils of the moults of trilobites can often be told from the fossils of the actual animals by whether the librigena are present. (The librigena, or cheek spines, detach during moulting.) In ptychopariids, short bladelike genal spines are often present on the tips of the librigena.
The thorax is large and is typically made up of eight or more segments. The thorax is usually much longer than the pygidium, which is usually small. In some species the pygidium is outlined with a flat border.
The Subclass Librostoma was recently erected to encompass several related orders, including Ptychopariida, Asaphida, Proetida, Harpetida, and possibly Phacopida. These are now known as the "Librostome Orders". Trilobites of the orders Proetida, Harpetida, and of the family Damesellidae were originally placed in Ptychopariida.Uuemaarahu
Uuemaarahu is a small, Baltic Sea islet comprising 0.0234 hectares belonging to the country of Estonia.
Uuemaarahu lies 1 kilometer to the southeast of the island of Hellamaa in the Väinameri Strait. It belongs to the administrative municipality of Pühalepa Parish, Hiiu County (Estonian: Hiiu maakond) and is part of the Hiiumaa Islet Landscape Reserve. Other islands nearby include Uuemererahu, Kadakalaid, Ramsi, Hõralaid and Vohilaid.
The islet is an important moulting area for an abundant variety of birds such as: the mute swan, the great black-backed gull, the common gull, the oystercatcher, the Arctic tern, the common eider, the greylag goose, the common goldeneye, the mallard, the goosander, the ruff, the black-tailed godwit, and the barnacle goose.