Butterfly And Bombyx mori

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A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured wings, and conspicuous, fluttering flightSony VAIO PCG-31114V battery. Butterflies comprise the true butterflies (superfamily Papilionoidea), the skippers (superfamily Hesperioidea) and the moth-butterflies (superfamily Hedyloidea). All the many other families within the Lepidoptera are referred to as moths. The earliest known butterfly fossils date to the mid Eocene epoch, between 40–50 million years agoSony VAIO PCG-31113V battery.

Butterflies exhibit polymorphism, mimicry and aposematism. Some, like the Monarch, will migrate over long distances. Some butterflies have evolved symbiotic and parasitic relationships with social insects such as ants. Some species are pests because in their larval stages they can damage domestic crops or treesSony VAIO PCG-31112V battery; however, some species are agents of pollination of some plants, and caterpillars of a few butterflies (e.g., Harvesters) eat harmful insects. Culturally, butterflies are a popular motif in the visual and literary arts.

Etymology

The name is derived from Middle English buterflie, butturflye, boterflye, from Old English butorflēoge, buttorflēoge, buterflēoge, perhaps a compound of butor (beater), mutation of bēatan (to beat), and flēoge (fly). Sony VAIO PCG-31111V battery

Alternate etymology connects the first element to butere (butter) as the name may have originally been applied solely to butterflies of a yellowish or butter-colour. This may have merged later with the belief that butterflies ate milk and butter (compare Middle High German molkendiep -literally “milk-thief”; Modern German Molkendieb and Low German BotterlickerSony VAIO PCG-31114M battery - literally “butter-licker”), or that they excreted a butter-like substance (compare Middle Dutch boterschijte - literally “butter-shitter”, also Middle Dutch botervliege, Dutch botervlieg, German butterfliege).

Life cycle

It is a popular belief that butterflies have very short life spans.[by whom?] However, butterflies in their adult stage can live from a week to nearly a year depending on the species. Many species have long larval life stages while others can remain dormant in their pupal or egg stages and thereby survive winters. Sony VAIO PCG-31113M battery

Butterflies may have one or more broods per year. The number of generations per year varies from temperate to tropical regions with tropical regions showing a trend towards multivoltinism.

Eggs

Egg of Ariadne merione

Butterfly eggs are protected by a hard-ridged outer layer of shell, called the chorion. This is lined with a thin coating of wax which prevents the egg from drying out before the larva has had time to fully developSony VAIO PCG-31112M battery. Each egg contains a number of tiny funnel-shaped openings at one end, called micropyles; the purpose of these holes is to allow sperm to enter and fertilize the egg. Butterfly and moth eggs vary greatly in size between species, but they are all either spherical or ovate.

Butterfly eggs are fixed to a leaf with a special glue which hardens rapidly. As it hardens it contracts, deforming the shape of the eggSony VAIO PCG-31111M battery. This glue is easily seen surrounding the base of every egg forming a meniscus. The nature of the glue is unknown and is a suitable subject for research. The same glue is produced by a pupa to secure the setae of the cremaster. This glue is so hard that the silk pad, to which the setae are glued, cannot be separatedSony VAIO PCG-41111V battery.

Eggs are almost invariably laid on plants. Each species of butterfly has its own hostplant range and while some species of butterfly are restricted to just one species of plant, others use a range of plant species, often including members of a common family.

The egg stage lasts a few weeks in most butterflies but eggs laid close to winter, especially in temperate regions, go through a diapause (resting) stageSony VAIO PCG-41112M battery, and the hatching may take place only in spring. Other butterflies may lay their eggs in the spring and have them hatch in the summer. These butterflies are usually northern species, such as the Mourning Cloak (Camberwell Beauty) and the Large and Small Tortoiseshell butterflies.Sony VAIO PCG-41111M battery

Caterpillars

Caterpillars of Junonia coenia.

Butterfly larvae, or caterpillars, consume plant leaves and spend practically all of their time in search of food. Although most caterpillars are herbivorous, a few species such as Spalgis epius and Liphyra brassolis are entomophagous (insect eating).

Some larvae, especially those of the Lycaenidae, form mutual associations with ants. They communicate with the ants using vibrations that are transmitted through the substrate as well as using chemical signals. SONY VAIO PCG-21214V batteryThe ants provide some degree of protection to these larvae and they in turn gather honeydew secretions.

Caterpillars mature through a series of stages called instars. Near the end of each instar, the larva undergoes a process called apolysis, in which the cuticle, a tough outer layer made of a mixture of chitin and specialized proteins, is released from the softer epidermis beneath, and the epidermis begins to form a new cuticle beneathSONY VAIO PCG-21213V battery. At the end of each instar, the larva moults the old cuticle, and the new cuticle expands, before rapidly hardening and developing pigment. Development of butterfly wing patterns begins by the last larval instar.

Butterfly caterpillars have three pairs of true legs from the thoracic segments and up to 6 pairs of prolegs arising from the abdominal segments. These prolegs have rings of tiny hooks called crochets that help them grip the substrate.SONY VAIO PCG-21212V battery

Some caterpillars have the ability to inflate parts of their head to appear snake-like. Many have false eye-spots to enhance this effect. Some caterpillars have special structures called osmeteria which are everted to produce smelly chemicals. These are used in defense.

Host plants often have toxic substances in them and caterpillars are able to sequester these substances and retain them into the adult stageSONY VAIO PCG-21212M battery. This makes them unpalatable to birds and other predators. Such unpalatibility is advertised using bright red, orange, black or white warning colours, a practice known as aposematism. The toxic chemicals in plants are often evolved specifically to prevent them from being eaten by insects. Insects in turn develop countermeasures or make use of these toxins for their own survivalSONY VAIO PCG-21211M battery. This "arms race" has led to the coevolution of insects and their host plants.[7]

Wing development

Last instar wing disk, Junonia coenia

Detail of a butterfly wing

Wings or wing pads are not visible on the outside of the larva, but when larvae are dissected, tiny developing wing disks can be found on the second and third thoracic segments, in place of the spiracles that are apparent on abdominal segmentsSONY VAIO PCG-51212M battery. Wing disks develop in association with a trachea that runs along the base of the wing, and are surrounded by a thin peripodial membrane, which is linked to the outer epidermis of the larva by a tiny duct.

Wing disks are very small until the last larval instar, when they increase dramatically in size, are invaded by branching tracheae from the wing base that precede the formation of the wing veins, and begin to develop patterns associated with several landmarks of the wingSONY VAIO PCG-51211M battery.

Near pupation, the wings are forced outside the epidermis under pressure from the hemolymph, and although they are initially quite flexible and fragile, by the time the pupa breaks free of the larval cuticle they have adhered tightly to the outer cuticle of the pupa (in obtect pupae). Within hours, the wings form a cuticle so hard and well-joined to the body that pupae can be picked up and handled without damage to the wings. SONY VAIO PCG-51112M battery

Pupa

Chrysalis of Gulf Fritillary

When the larva is fully grown, hormones such as prothoracicotropic hormone (PTTH) are produced. At this point the larva stops feeding and begins "wandering" in the quest of a suitable pupation site, often the underside of a leaf.

The larva transforms into a pupa (or chrysalis) by anchoring itself to a substrate and moulting for the last time. The chrysalis is usually incapable of movement, although some species can rapidly move the abdominal segments or produce sounds to scare potential predatorsSONY VAIO PCG-51111M battery.

The pupal transformation into a butterfly through metamorphosis has held great appeal to mankind. To transform from the miniature wings visible on the outside of the pupa into large structures usable for flight, the pupal wings undergo rapid mitosis and absorb a great deal of nutrients. If one wing is surgically removed early onSONY VAIO PCG-51111V battery, the other three will grow to a larger size. In the pupa, the wing forms a structure that becomes compressed from top to bottom and pleated from proximal to distal ends as it grows, so that it can rapidly be unfolded to its full adult size. Several boundaries seen in the adult color pattern are marked by changes in the expression of particular transcription factors in the early pupa. SONY VAIO PCG-81211V battery

Adult or imago

The adult, sexually mature, stage of the insect is known as the imago. As Lepidoptera, butterflies have four wings that are covered with tiny scales (see photo). The fore and hindwings are not hooked together, permitting a more graceful flight. An adult butterfly has six legs, but in the nymphalids, the first pair is reduced. After it emerges from its pupal stageSONY VAIO PCG-81111V battery, a butterfly cannot fly until the wings are unfolded. A newly emerged butterfly needs to spend some time inflating its wings with blood and letting them dry, during which time it is extremely vulnerable to predators. Some butterflies' wings may take up to three hours to dry while others take about one hour. Most butterflies and moths will excrete excess dye after hatching. This fluid may be white, red, orange, or in rare cases, blue. SONY VAIO PCG-81212M battery

External morphology

Adult butterflies have four wings: a forewing and hindwing on both the left and the right side of the body. The body is divided into three segments: the head, thorax, and the abdomen. They have two antennae, two compound eyes, and a proboscis.

Scales

Butterflies are characterized by their scale-covered wings. The coloration of butterfly wings is created by minute scalesSony VAIO PCG-81112M battery. These scales are pigmented with melanins that give them blacks and browns, but blues, greens, reds and iridescence are usually created not by pigments but the microstructure of the scales. This structural coloration is the result of coherent scattering of light by the photonic crystal nature of the scales. The scales cling somewhat loosely to the wing and come off easily without harming the butterflySONY VAIO PCG-71111M battery.

Polymorphism

Main article: Polymorphism (biology)

Many adult butterflies exhibit polymorphism, showing differences in appearance. These variations include geographic variants and seasonal forms. In addition many species have females in multiple forms, often with mimetic forms. Sexual dimorphism in coloration and appearance is widespread in butterfliesSONY VAIO PCG-7192V battery. In addition many species show sexual dimorphism in the patterns of ultraviolet reflectivity, while otherwise appearing identical to the unaided human eye. Most of the butterflies have a sex-determination system that is represented as ZW with females being the heterogametic sex (ZW) and males homogametic (ZZ). SONY VAIO PCG-7191V battery

Genetic abnormalities such as gynandromorphy also occur from time to time. In addition many butterflies are infected by Wolbachia and infection by the bacteria can lead to the conversion of males into females[12] or the selective killing of males in the egg stage.[13]

Mimicry

The Heliconius butterflies from the tropics of the Western Hemisphere are the classical model for Müllerian mimicry.SONY VAIO PCG-7196M battery

Batesian and Mullerian mimicry in butterflies is common. Batesian mimics imitate other species to enjoy the protection of an attribute they do not share, aposematism in this case. The Common Mormon of India has female morphs which imitate the unpalatable red-bodied swallowtails, the Common Rose and the Crimson RoseSONY VAIO PCG-7195M battery. Mullerian mimicry occurs when aposematic species evolve to resemble each other, presumably to reduce predator sampling rates, the Heliconius butterflies from the Americas being a good example.

Wing markings called eyespots are present in some species; these may have an automimicry role for some species. In others, the function may be intraspecies communicationSONY VAIO PCG-7194M battery, such as mate attraction. In several cases, however, the function of butterfly eyespots is not clear, and may be an evolutionary anomaly related to the relative elasticity of the genes that encode the spots.[15][16]

Seasonal polyphenism

Many of the tropical butterflies have distinctive seasonal forms. This phenomenon is termed seasonal polyphenism and the seasonal forms of the butterflies are called the dry-season and wet-season formsSONY VAIO PCG-7192M battery. How the season affects the genetic expression of patterns is still a subject of research.[17] Experimental modification by ecdysone hormone treatment has demonstrated that it is possible to control the continuum of expression of variation between the wet and dry-season forms.[18] The dry-season forms are usually more cryptic and it has been suggested that the protection offered may be an adaptationSONY PCG-8113M battery. Some also show greater dark colours in the wet-season form which may have thermoregulatory advantages by increasing ability to absorb solar radiation.[19]

Bicyclus anynana is a species of butterfly that exhibits a clear example of seasonal polyphenism. These butterflies, endemic to Africa, have two distinct phenotypic forms that alternate according to the seasonSONY PCG-8112M battery. The wet-season forms have large, very apparent ventral eyespots whereas the dry-season forms have very reduced, oftentimes nonexistent, ventral eyespots. Larvae that develop in hot, wet conditions develop into wet-season adults whereas those growing in the transition from the wet to the dry season, when the temperature is declining, develop into dry-season adults. SONY PCG-7134M battery This polyphenism has an adaptive role in B. anynana. In the dry-season it is disadvantageous to have conspicuous eyespots because B. anynana blend in with the brown vegetation better without eyespots. By not developing eyespots in the dry-season they can more easily camouflage themselves in the brown brush. This minimizes the risk of visually mediated predationSONY PCG-7131M battery. In the wet-season, these brown butterflies cannot as easily rely on cryptic coloration for protection because the background vegetation is green. Thus, eyespots, which may function to decrease predation, are beneficial for B. anynana to express.[21]

Habits

Antennal shape in the Lepidoptera from C. T. Bingham (1905)

The Australian painted lady feeding on a flowering shrub

Butterflies feed primarily on nectar from flowers. Some also derive nourishment from pollen,[22] tree sap, rotting fruit, dung, decaying fleshSONY PCG-7122M battery , and dissolved minerals in wet sand or dirt. Butterflies are important as pollinators for some species of plants although in general they do not carry as much pollen load as bees. They are however capable of moving pollen over greater distances.[23] Flower constancy has been observed for at least one species of butterfly. SONY PCG-7121M battery

As adults, butterflies consume only liquids which are ingested by means of their proboscis. They sip water from damp patches for hydration and feed on nectar from flowers, from which they obtain sugars for energy as well as sodium and other minerals vital for reproduction. Several species of butterflies need more sodium than that provided by nectar and are attracted by sodium in saltSONY PCG-7113M battery; they sometimes land on people, attracted by the salt in human sweat. Some butterflies also visit dung, rotting fruit or carcasses to obtain minerals and nutrients. In many species, this mud-puddling behaviour is restricted to the males, and studies have suggested that the nutrients collected may be provided as a nuptial gift along with the spermatophore, during mating. SONY PCG-7112M battery

Butterflies use their antennae to sense the air for wind and scents. The antennae come in various shapes and colours; the hesperids have a pointed angle or hook to the antennae, while most other families show knobbed antennae. The antennae are richly covered with sensory organs known as sensillaeSONY PCG-8Z3M battery. A butterfly's sense of taste, 200 times stronger than humans,[26] is coordinated by chemoreceptors on the tarsi, or feet, which work only on contact, and are used to determine whether an egg-laying insect's offspring will be able to feed on a leaf before eggs are laid on it.[27] Many butterflies use chemical signals, pheromones, and specialized scent scales (androconia) and other structures SONY PCG-8Z2M battery (coremata or "hair pencils" in the Danaidae) are developed in some species.

Vision is well developed in butterflies and most species are sensitive to the ultraviolet spectrum. Many species show sexual dimorphism in the patterns of UV reflective patches.[28] Color vision may be widespread but has been demonstrated in only a few species.[29][30]

Some butterflies have organs of hearing and some species are also known to make stridulatory and clicking sounds.SONY PCG-8Z1M battery

Monarch butterflies

Many butterflies, such as the Monarch butterfly, are migratory and capable of long distance flights. They migrate during the day and use the sun to orient themselves. They also perceive polarized light and use it for orientation when the sun is hidden.[32]

Many species of butterfly maintain territories and actively chase other species or individuals that may stray into themSONY PCG-8Y3M battery. Some species will bask or perch on chosen perches. The flight styles of butterflies are often characteristic and some species have courtship flight displays. Basking is an activity which is more common in the cooler hours of the morning. Many species will orient themselves to gather heat from the sun. Some species have evolved dark wingbases to help in gathering more heat and this is especially evident in alpine forms. SONY PCG-8Y2M battery

Flight

Heteronympha merope taking off

See also Insect flight

Like many other members of the insect world, the lift generated by butterflies is more than what can be accounted for by steady-state, non-transitory aerodynamics. Studies using Vanessa atalanta in a windtunnel show that they use a wide variety of aerodynamic mechanisms to generate force. These include wake capture, vortices at the wing edgeSONY PCG-7Z1M battery, rotational mechanisms and Weis-Fogh 'clap-and-fling' mechanisms. The butterflies were also able to change from one mode to another rapidly.[34]

Migration

The Monarch butterfly migrates large distances

Main article: Lepidoptera migration

See also Insect migration

Many butterflies migrate over long distances. Particularly famous migrations are those of the Monarch butterfly from Mexico to northern USA and southern Canada, a distance of about 4000 to 4800 km (2500–3000 miles) SONY PCG-6W2M battery . Other well known migratory species include the Painted Lady and several of the Danaine butterflies. Spectacular and large scale migrations associated with the Monsoons are seen in peninsular India.[35] Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes. SONY PCG-5J5M battery

Butterflies have been shown to navigate using time compensated sun compasses. They can see polarized light and therefore orient even in cloudy conditions. The polarized light in the region close to the ultraviolet spectrum is suggested to be particularly important.[38]

It is suggested that most migratory butterflies are those that belong to semi-arid areas where breeding seasons are short. SONY PCG-5K2M battery  The life-histories of their host plants also influence the strategies of the butterflies.[40]

Defense

Wings of a butterfly (Leopard Lacewing Cethosia cyane) become increasingly damaged as they age, and do not repair

See also Defense in insects

Butterflies are threatened in their early stages by parasitoids and in all stages by predators, diseases and environmental factors. They protect themselves by a variety of means.

Chemical defenses are widespread and are mostly based on chemicals of plant originSONY PCG-5K1M battery. In many cases the plants themselves evolved these toxic substances as protection against herbivores. Butterflies have evolved mechanisms to sequester these plant toxins and use them instead in their own defense.[41] These defense mechanisms are effective only if they are also well advertised and this has led to the evolution of bright colours in unpalatable butterfliesSONY PCG-5J4M battery. This signal may be mimicked by other butterflies. These mimetic forms are usually restricted to the females.

Eyespots on wings of Speckled Wood, Pararge aegeria, appear to distract predators from attacking the head. The left hind wing has been badly damaged by birds, but the insect is alive and able to fly.

Cryptic coloration is found in many butterflies. Some like the oakleaf butterfly are remarkable imitations of leaves.SONY PCG-5J1M battery  As caterpillars, many defend themselves by freezing and appearing like sticks or branches. Some papilionid caterpillars resemble bird dropping in their early instars. Some caterpillars have hairs and bristly structures that provide protection while others are gregarious and form dense aggregations. Some species also form associations with ants and gain their protection (See Myrmecophile) SONY PCG-5G2M battery.

Behavioural defenses include perching and wing positions to avoid being conspicuous. Some female Nymphalid butterflies are known to guard their eggs from parasitoid wasps.[43]

Eyespots and tails are found in many lycaenid butterflies. It is thought that their function is to divert the attention of predators from the more vital head region. An alternative theory is that these cause ambush predators such as spiders to approach from the wrong end and allow for early visual detection. Sony VAIO PCG-8131M battery

A butterfly's hind wings are thought to allow them to take swift, tight turns to evade predators.[45]

Notable species

Rusty-tipped Page (Siproeta epaphus), Butterfly World (Florida)

There are between 15,000 and 20,000 species of butterflies worldwide. Some well-known species from around the world include:

Swallowtails and Birdwings, Family Papilionidae

Common Yellow Swallowtail, Papilio machaon

Spicebush Swallowtail, Papilio troilus

Lime Butterfly, Papilio demoleus

Ornithoptera genus (Birdwings; the largest butterflies)

Whites and Yellows, Family PieridaeSony VAIO PCG-8152M battery

Small White, Pieris rapae

Green-veined White, Pieris napi

Common Jezebel, Delias eucharis

Blues and Coppers or Gossamer-Winged Butterflies, Family Lycaenidae

Xerces Blue, Glaucopsyche xerces (extinct)

Karner Blue, Lycaeides melissa samuelis (endangered)

Red Pierrot, Talicada nyseus

Metalmark butterflies, Family Riodinidae

Duke of Burgundy, Hamearis lucina

Plum Judy, Abisara echerius

Brush-footed butterflies, Family Nymphalidae

Painted Lady, or Cosmopolitan, Vanessa cardui

Monarch butterfly, Danaus plexippus

Morpho genusSony VAIO PCG-31311M battery

Speckled Wood, Pararge aegeria

Skippers, Family Hesperiidae

Mallow Skipper, Carcharodus alceae

Zabulon Skipper, Poanes zabulon

In culture

Art

Artistic depictions of butterflies have been used in many cultures including Egyptian hieroglyphs 3500 years ago.[46]

In the ancient Mesoamerican city of Teotihuacan, the brilliantly colored image of the butterfly was carved into many temples, buildings, jewelry, and emblazoned on incense burners in particularSony VAIO PCG-31111M battery. The butterfly was sometimes depicted with the maw of a jaguar and some species were considered to be the reincarnations of the souls of dead warriors. The close association of butterflies to fire and warfare persisted through to the Aztec civilization and evidence of similar jaguar-butterfly images has been found among the Zapotec, and Mayan civilizationsSony VAIO PCG-8112M battery.

A serving tray decorated with butterfly wings

Today, butterflies are widely used in various objects of art and jewelry: mounted in frame, embedded in resin, displayed in bottles, laminated in paper, and used in some mixed media artworks and furnishings.[48] Butterflies have also inspired the "butterfly fairy" as an art and fictional character, including in the Barbie Mariposa filmSony VAIO PCG-7186M battery.

Symbolism

According to Kwaidan: Stories and Studies of Strange Things, by Lafcadio Hearn, a butterfly was seen in Japan as the personification of a person's soul; whether they be living, dying, or already dead. One Japanese superstition says that if a butterfly enters your guestroom and perches behind the[bamboo screen, the person whom you most love is coming to see youSony VAIO PCG-7171M battery. However, large numbers of butterflies are viewed as bad omens. When Taira no Masakado was secretly preparing for his famous revolt, there appeared in Kyoto so vast a swarm of butterflies that the people were frightened — thinking the apparition to be a portent of coming evil.[49]

The Russian word for "butterfly", бабочка (bábochka), also means "bow tie". It is a diminutive of "baba" or "babka" (= "woman, grandmother, cake"), whence also "babushka" = "grandmother"Sony VAIO PCG-9Z1M battery.

The ancient Greek word for "butterfly" is ψυχή (psȳchē), which primarily means "soul" or "mind".[50]

According to Mircea Eliade's Encyclopedia of Religion, some of the Nagas of Manipur trace their ancestry from a butterfly.

Butterfly and Chinese wisteriaflowers, by Xü Xi (c.886–c.975), painted around 970 during the early Song DynastySony VAIO PCG-5S1M battery.

In Chinese culture, two butterflies flying together symbolize love. Also, Butterfly Lovers is a famous Chinese folktale. The Taoist philosopher, Zhuangzi, once had a dream about being a butterfly that flew without care about humanity; however; when he awoke and realized that it was just a dream, he thought to himself, "Was I before a man who dreamt about being a butterfly, or am I now a butterfly who dreams about being a manSony VAIO PCG-5P1M battery?"

In some old cultures, butterflies also symbolize rebirth after being inside a cocoon for a period of time.

Jose Rizal delivered a speech in 1884 at a banquet and mentioned "the Oriental chrysalis ... is about to leave its cocoon", comparing the emergence of a "new Philippines" with that of butterfly metamorphosis. Sony VAIO PCG-5N2M battery He has also often used the butterfly imagery in his poems and other writings to express the Spanish Colonial Filipinos' longing for liberty.[53] Much later, in a letter to Ferdinand Blumentritt, Rizal compared his life in exile to a weary butterfly with sun-burnt wings.

Der Schmetterlingsjäger (The butterfly hunter) by Carl Spitzweg (1840), a depiction from the era of butterfly collectionSony VAIO PCG-3C2M battery.

Some people say that when a butterfly lands on you it means good luck.[citation needed] However, in Devonshire, people would traditionally rush around to kill the first butterfly of the year that they see, or else face a year of bad luck.[55] Also, in the Philippines, a lingering black butterfly or moth in the house is taken to mean that someone in the family has died or will soon die. Sony VAIO PCG-8161M battery

The idiom "butterflies in the stomach" is used to describe a state of nervousness.

In the NBC television show Kings, butterflies are the national symbol of the fictional nation of Gilboa and a sign of God's favor.

Technological inspiration

Researches on the wing structure of Palawan Birdwing butterflies led to new wide wingspan kite and aircraft designs.[57]

Studies on the reflection and scattering of light by the scales on wings of swallowtail butterflies led to the innovation of more efficient light-emitting diodes. Sony VAIO PCG-8141M battery

The structural coloration of butterflies is inspiring nanotechnology research to produce paints that do not use toxic pigments and in the development of new display technologies.

The discoloration and health of butterflies in butterfly farms, is now being studied for use as indicators of air quality in several cities.

The silkworm is the larva or caterpillar of the domesticated silkmoth, Bombyx mori (Latin: "silkworm of the mulberry tree")Sony VAIO PCG-3J1M battery. It is an economically important insect, being a primary producer of silk. A silkworm's preferred food is white mulberry leaves, but it may also eat the leaves of any other mulberry tree (i.e., Morus rubra or Morus nigra)[citation needed] as well as the Osage Orange. It is entirely dependent on humans for its reproduction and does not occur naturally in the wildSony VAIO PCG-3H1M battery. Sericulture, the practice of breeding silkworms for the production of raw silk, has been underway for at least 5,000 years in China,[1] from where it spread to Korea and Japan, and later to India and the West. The silkworm was domesticated from the wild silkmoth Bombyx mandarina which has a range from northern India to northern China, KoreaSony VAIO PCG-3F1M battery, Japan and far the eastern regions of Russia. The domesticated silkworm derives from Chinese rather than Japanese or Korean stock.[2][3] It is unlikely that silkworms were domestically bred before the Neolithic age: it was not until then that the tools required to facilitate the manufacturing of larger quantities of silk thread had been developed
Sony VAIO PCG-3C1M battery
. The domesticated B. mori and the wild B. mandarina can still breed and sometimes produce hybrids.

Types

Mulberry silkworms can be categorized into 3 different, but connected groups or types. The major groups of silkworms fall under the univoltine and bivoltine categories. The Univoltine breed is generally linked with the geographical area within greater Europe. The eggs of this type hibernate during winter due to the cold climate, and cross fertilise only by springSony VAIO PCG-9Z2L battery, generating silk only once annually. The second type of breed is called Bivoltine and is normally found in Asian regions such as China, Japan, and Korea. The breeding process of this type takes place twice annually, a feat made possible through the slightly warmer climates and the resulting two lifecycles. The Polyvoltine breed of mulberry silkworm can only be located in the tropicsSony VAIO PCG-9Z1L battery. The eggs are laid by female moths and hatch within nine to twelve days, so the resulting type can have up to 8 separate lifecycles throughout the year.[5]

Process

Eggs take about fourteen days to hatch into larvae, which eat continuously. They have a preference for white mulberry, having an attraction to the mulberry odorant cis-jasmone. They are not monophagous since they can eat other species of Morus as well as some other MoraceaeSony VAIO PCG-9131L battery. Their droppings are black. Hatchlings and second-instar larvae are called kego and chawki in India. They are covered with tiny black hairs. When the color of their heads turns darker, it indicates that they are about to molt. After molting, the instar phase of the silkworm emerges white, naked, and with little horns on the backs.

After they have molted four times (i.e., in the fifth instar phase), their bodies become slightly yellow and the skin becomes tighterSony VAIO PCG-8161L battery. The larvae will then enter the pupa phase of their life cycle and enclose themselves in a cocoon made up of raw silk produced by the salivary glands. The cocoon provides a vital layer of protection during the vulnerable, almost motionless pupal state. Many other Lepidoptera produce cocoons, but only a few—the Bombycidae, in particular the Bombyx genusSony VAIO PCG-8152L battery, and the Saturniidae, in particular the Antheraea genus—have been exploited for fabric production.

If the animal is allowed to survive after spinning its cocoon and through the pupa phase of its life cycle, it will release proteolytic enzymes to make a hole in the cocoon so that it can emerge as a moth. These enzymes are destructive to the silk and can cause the silk fibers to break down from over a mile in length to segments of random length, which ruins the silk threadsSony VAIO PCG-8141L battery. To prevent this, silkworm cocoons are boiled. The heat kills the silkworms and the water makes the cocoons easier to unravel. Often, the silkworm itself is eaten (see Cuisine). The moth – the adult phase of the life cycle – cannot fly. Silkmoths have a wingspan of 3–5 cm (1.5–2 inches) and a white hairy body. Females are about two to three times bulkier than males (for they are carrying many eggs) Sony VAIO PCG-8131L battery, but are similarly colored. Adult Bombycidaes have reduced mouth parts and do not feed, though a human caretaker can also[clarification needed] feed them.

Cocoon

Cocoon

The cocoon is made of a thread of raw silk from 300 to about 900 meters (1,000 to 3,000 feet) long. The fibers are very fine and lustrous, about 10 micrometers (1/2,500th of an inch) in diameter. About 2,000 to 3,000 cocoons are required to make a pound of silk (0,4kg) Sony VAIO PCG-81312L battery. At least 70 million pounds of raw silk are produced each year, requiring nearly 10 billion pounds of mulberry leaves. The FAO estimates the world production of raw silk at 164971 tonnes in 2009[6] . According to E. L. Palmer, one pound of silk represents about 1,000 miles of filament. The annual world production represents 70 billion miles of silk filament. This silk is usually processed to remove natural waxes or gums such as the sericinSony VAIO PCG-81214L battery, a water-soluble protective layer that solidifies immediately when exposed to air. It is sometimes subsequently dyed.

Research

Due to its miniature size and ease of culture, the silkworm has become a model organism in the study of Lepidopteran and arthropod biology. Fundamental findings on pheromones, hormones, brain structures and physiology have been made with the silkworm. One example of this was the molecular identification of the first known pheromoneSony VAIO PCG-81115L battery, bombykol which required extracts from 500,000 individuals, due to the very small quantities of pheromone produced by any individual worm.[citation needed]

Currently, research is focusing on genetics of silkworms and the possibility of genetic engineering. Many hundreds of strains are maintained, and over 400 Mendelian mutations have been described. Sony VAIO PCG-81114L batteryAnother source suggests 1000 inbred domesticated strains are kept worldwide.[8] One useful development for the silk industry are silkworms that can feed on food other than mulberry leaves, including an artificial diet.[citation needed] Research on the genome also raises the possibility of genetically engineering silkworms to produce proteins, including pharmacological drugs, in the place of silk proteinsSony VAIO PCG-81113L battery.

Kraig Biocraft Laboratories[9] has used research from the Universities of Wyoming and Notre Dame in a collaborative effort to create a silkworm that is genetically altered to produce spider silk. In September 2010 it was announced at a press conference at the University of Notre Dame that the effort had been successful. Sony VAIO PCG-7142L battery

In January 2010, National University of Singapore together with Republic Polytechnic were in the process of creating "super" silk.[11] The "super" silk are produced by coaxing "silkworms to spin stronger silk by exposing them (silkworms) to an electric field before they (silkworms) spin" .[12] Silk produced through this new method is so strong as to be bullet-proofSony VAIO PCG-7141L battery.

Researchers at Tufts developed scaffolds made of spongy silk that feel and look similar to human tissue. They are implanted during reconstructive surgery to support or restructure damaged ligaments, tendons, and other tissue. They also created implants made of silk and drug compounds which can be implanted under the skin for steady and gradual time release of medications. Sony VAIO PCG-71111L battery

Domestication

The domesticated variety, compared to the wild form, has increased cocoon size, growth rate and efficiency of its digestion. It has also gained tolerance to human presence and handling and living in crowded conditions. It also cannot fly and lacks fear of potential predators. These changes have made it entirely dependent upon humans for survival.Sony VAIO PCG-61411L battery

Silkworm breeding

Pupa

The silkworm is one of the world's most genetically modified animals. Silkworms were first domesticated in China over 5000 years ago.[15][16] Since then, the silk production capacity of the species has increased nearly tenfold. Silkworm is one of the few organisms wherein the principles of genetics and breeding were applied to harvest maximum outputSony VAIO PCG-61112L battery. It is next only to maize in exploiting the principles of 'heterosis' and 'cross breeding'. Silkworm breeding is aimed at the overall improvement of silkworm from a commercial point of view. The major objectives of silkworm breeding are improving fecundity, healthiness of larvae, quantity of cocoon and silk production, disease resistance, etc. Fecundity refers to the egg laying capacity of a breedSony VAIO PCG-61111L battery. It is a very important factor, since commercial sericulture is strongly dependent on silkworm egg availability. Healthiness of larvae leads to a healthy cocoon crop. Healthiness is dependent on factors such as better pupation rate, fewer dead larvae in the mountage, shorter larval duration (the shorter the larval duration, the lesser the chances of infection) and bluish tinged fifth instar larvaeSony VAIO PCG-5T4L battery (it is observed that bluish colored fifth instar larvae are healthier than the reddish brown ones). Quantity of cocoon and silk produced is directly related to the pupation rate and larval weight. Healthier larvae have greater pupation rates and cocoon weights. Quality of cocoon and silk depends on a number of factors including genetics. Specific purposes apart from commercial purpose are given attention by advanced countries to breed development for specific purposes like sericin productionSony VAIO PCG-5T3L battery, sex limited breeds, thin/thick filament production etc. Disease resistance breeding is important, as the major reason for crop losses is pathogen infection. Efforts are being made to select breeds which are tolerant or resistant to various pathogens. [1]

Silkworm raising as hobby and school science project

In the USA, teachers may sometimes introduce insect life cycle to their students by raising silkworms in the classroom as a science project. Students have a chance to observe complete life cycles of insect from egg stage to larvae, pupa, moth and eggsSony VAIO PCG-5T2L battery.

The silkworm has been raised as a hobby in China and South Africa. Children often pass on the eggs, creating a noncommercial population. The experience provides children with the opportunity to witness the lifecycle of silkworms. The practice of raising silkworms by children as pets has, in the non-silkfarming country of South Africa, led to the development of extremely hardy landraces of silkwormSony VAIO PCG-5S3L battery. This is because they are invariably subjected to hardships not encountered by commercially-farmed members of the species.[17] However, these worms, not being selectively bred as such, are possibly inferior in silk production and may exhibit other undesirable traits.

Genome

The full genome of the silkworm was published in 2008 by the International Silkworm Genome Consortium. Sony VAIO PCG-5S2L battery

The genome of the silkworm is mid-range with a genome size of ~432 Mb. It was published in 2008 by the International Silkworm Genome Consortium.[8] A draft sequence was published in 2004.[18]

High genetic variability has been found in domestic lines of silkworms, though this is less than that among wild silkmoths (~83%)Sony VAIO PCG-5S1L battery. This suggests a single event of domestication, and that it happened over a short period of time, with a large number of wild worms having been collected for domestication.[19] Major questions, however, remain unanswered: “Whether this event was in a single location or in a short period of time in several locations cannot be deciphered from the data,” Research also has yet to identify the area in China where domestication arose. Sony VAIO PCG-5R2L battery

Cuisine

Silkworm pupae dishes

Like many insect species, silkworm pupae are eaten in some cultures (see Entomophagy). This unusual food may go by the English phrase "ground cucumber."

In Assam, India, they are boiled for extracting silk and the boiled pupa is taken directly with salt or fried with chilli pepper and or herbs to take as snack or dish.

In Korea, they are boiled and seasoned to make a popular snack food known as beondegi.

In China, street vendors sell roasted silkworm pupaeSony VAIO PCG-5R1L battery.

In Vietnam, this is known as con nhộng.

Silkworms have also been proposed for cultivation by astronauts as space food on long-term missions.[21]

Silkworm legends

In China, there is a legend that the discovery of the silkworm's silk was by an ancient empress Lei Zu, the wife of the Yellow Emperor and the daughter of XiLing-Shi. She was drinking tea under a tree when a silk cocoon fell into her teaSony VAIO PCG-5P4L battery. As she picked it out and started to wrap the silk thread around her finger, she slowly felt a warm sensation. When the silk ran out, she saw a small larva. In an instant, she realized that this caterpillar larva was the source of the silk. She taught this to the people and it became widespread. There are many more legends about the silkwormSony VAIO PCG-5P2L battery.

The Chinese guarded their knowledge of silk, but, according to one story, a Chinese princess given in marriage to a Khotan prince brought to the oasis the secret of silk-manufacture, "hiding silkworms in her hair as part of her dowry", probably in the first half of the 1st century CE.[22] It is also said that about AD 550, Christian monks smuggled silkworms, in a hollow stick, out of China and sold the secret to the Byzantine EmpireSony VAIO PCG-5N4L battery.

Silkworm diseases

Nosema bombycis is a microsporidium that kills 100% of silkworms hatched from infected eggs. This disease can be carried over from worms to moths, then eggs and worms again. This microsporidium comes from the food that silkworms eat. If silkworms get this microsporidium in their worm stage, there are no visible symptomsSony VAIO PCG-5N2L battery. However, mother moths will pass the disease onto the eggs, and 100% of worms hatching from the diseased eggs will die in their worm stage. To prevent this disease, it is therefore extremely important to rule out all eggs from infected moths by checking the moth’s body fluid under a microscopeSony VAIO PCG-51513L battery.

Botrytis bassiana is a fungus that destroys the entire silkworm body. This fungus usually appears when silkworms are raised under cold conditions with high humidity. This disease is not passed on to the eggs from moths, as the infected silkworms cannot survive to the moth stage. This fungus can spread to other insectsSony VAIO PCG-51511L battery.

Grasserie: If grasserie is observed in chawkie stage, then the chawkie larvae must have been infected while hatching or during chawkie rearing. Infected eggs can be disinfected by cleaning their surface prior to hatching. Infections can occur as a result of improper hygiene in the chawkie rearing house. This disease develops faster in early instar rearingSony VAIO PCG-51412L battery.

Pebrine is a disease caused by a parasitic microsporidian, Nosema bombycis Nageli. Diseased larvae show slow growth, an undersized, pale and flaccid body, and poor appetite. Tiny black spots appear on larval integument. Additionally, dead larvae will remain rubbery and do not undergo putrefaction after deathSony VAIO PCG-51411L battery.

Traditional Chinese medicine

Silkworm is the source of the "stiff silkworm", which is made from dried 4th or 5th instar larvae which have died of white muscardine disease (a lethal fungal infection). Its uses are to dispel flatulence, dissolve phlegm and relieve spasmsSony VAIO PCG-51312L battery.

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