Mulberry Silkworm: History, Habitat and Life Cycle

Mulberry Silkworm: History, Habitat and Life Cycle

In this article we will discuss about Mulberry Silkworm:- 1. History of Mulberry Silkworm 2. Habit and Habitat of Mulberry Silkworm 3. External Features 4. Life Cycle 5. Economic Importance 6. Diseases 7. Other Silkworm Moths.

History of Mulberry Silkworm:

Bombyx mori is popularly called the Chinese silkworm or Mulberry silkworm moth. It is well known for genuine silk. The importance of silkworm in silk production was known in China during 3500 B.C. The Chinese people knew the methods for cultivating silk and of preparing cloth from it for more than 2000 years. The rearing of silk moth and production of raw silk is known as sericulture.

The art of sericulture was held by Chinese a very close secret, so much so, that the leakage of any information or attempt to export eggs or living cocoons was punishable with death. Even then silk was after all introduced in Europe by two monks, who were sent to China as spies.

They studied the nature, source and art of silkworm rearing and stealthily carried some eggs in their pilgrim’s staff to Constantinople in 555 A.D.

From this place the silkworm-rearing was spread into the Mediterranean and Asiatic countries including India, Burma, Thailand and Japan. The insect breeders have produced many races of silkworm moth by hybridisation to meet the requirements of climate, rapidity of reproduction, quality, colour and yield of silk.

Habit and Habitat of Mulberry Silkworm:

Bombyx mori or the Mulberry silkworm is completely domesticated organism and is never found wild. The adult moths seldom eat and are primarily concerned with reproduction.

Their larvae are voracious eaters. They feed on the leaves of mulberry trees. Some moths are single brooded or univoltine and others are many brooded or multivoltine. Owing to domestication, a large number of strains have evolved out, which produce cocoons of various shapes, sizes, weights and colours ranging from white to yellow.

Only one generation is produced in one year by worms in Europe and other countries where the length of winters far exceeds the duration of summers. Some strains pass through two to seven broods and are cultivated in warm climates. In South India, particularly Mysore, Coimbatore and Salem, a strain which produces several generations, extensively utilised to produce silk.

External Features of Mulberry Silkworm:

The adult moth is about 25.00 mm long with a wing-span of 40.00 to 50.00 mm. The female silk moths are larger than the males. The moth is quite robust and creamy-white in colour. The body is distinctly divisible into three regions, namely head, thorax and abdomen.

The head bears a pair of compound eyes, a pair of branched or feathery antennae and the mouth parts. The thorax bears three pairs of legs and two pairs of wings. The cream-coloured wings are about 25.00 mm long and are marked by several faint or brown lines. The entire body is covered by minute scales.

Life Cycle of Mulberry Silkworm:

The silk moth is dioecious, i.e., the sexes are separate. Fertilisation is internal, preceded by copulation. The development includes a complicated metamorphosis.

After fertilisation, each female moth lays about 300 to 400 eggs. These eggs are placed in clusters on the leaves of mulberry tree. The female covers the eggs by a gelatinous secretion which glues them to the surface of the leaves. The eggs are small, oval and usually slightly yellowish in colour. The egg contains a good amount of yolk and is covered by a smooth hard chitinous shell.

After laying the eggs the female moth does not take any food and dies within 4-5 days. In the univoltine (a single brood per year) they may take months because overwintering takes place in this stage but the multivoltine broods come out after 10-12 days. From the egg hatches out a larva called the caterpillar.

Larva:

The larva of silkworm moth is called caterpillar larva. The newly hatched larva is about 4.00 to 6.00 mm in length. It has a rough, wrinkled, hairless and yellowish white or greyish worm-like body. The full grown larva is about 6.00 to 8.00 cm in length. The body of larva is distinguishable into a prominent head, distinctly segmented thorax and an elongated abdomen. The head bears mandibulate mouth and three pairs of ocelli.

A distinct hook-like structure, the spinneret, is present for the extrusion of silk from the inner silk-gland. The thorax forms a hump and consists of three segments. Each of the three thoracic segments bears pair of jointed true legs. The tip of each leg has a recurved hook for locomotion and ingestion of leaves.

The abdomen consists of ten segments of which first nine are clearly marked, while the tenth one is indistinct. The third, fourth, fifth, sixth and ninth abdominal segments bear ventrally a pair of un-jointed stumpy appendages each.

These are called pro-legs or pseudo-legs. Each leg is retractile and more or less cylindrical. The eighth segment carries a short dorsal anal horn. A series of respiratory spiracles or ostia are present on either lateral side of the abdomen.

The larva is a voracious eater and strongly gregarious. In the beginning chopped young mulberry leaves are given as food but with the advancement of age entire and matured leaves are provided as food. The caterpillar moves in a characteristic looping manner. The larval life lasts for 2-3 weeks. During this period the larva moults four times.

After each moult, the larva grows rapidly. A full-grown larva is about 8.00 cm long and becomes transparent and golden brown in appearance. A pair of long sac-like silk-glands now develops into the lateral side of the body. These are modified salivary glands.

The full-grown larva now stops feeding and hides itself in a corner under the leaves. It now begins to secrete the clear and sticky fluid of its salivary glands through a narrow pore called the spinneret situated on the hypo pharynx. The sticky substance turns into a fine, long and solid thread or filament of silk into the air.

The thread becomes wrapped around the body of the caterpillar larva forming a complete covering or pupal case called the cocoon. The cocoon-formation takes about 3-4 days. The cocoon serves a comfortable house for the protection of the caterpillar larva for further development.

The cocoon is a white or yellow, thick, oval capsule which is slightly narrow in the middle.

It is formed of a single long continuous thread. The outer threads, which are initial filaments of the cocoon, are irregular but the inner ones forming later the actual bed of the pupa, is one long continuous thread about 300 metres in length, wound round in concentric rings by constant motion of the head from one side to the other about 65 times per minute.

The irregular surface threads are secreted first and the inner continuous thread later. The silk thread is secreted at the rate of 150 mm per minute. Within a fortnight the caterpillar larva transforms into a conical brownish creature called the pupa or the chrysalis.

The pupa lies dormant, but undergoes very important active changes which are referred to as metamorphosis. The larval organs such as abdominal pro-legs, anal horn and mouth parts are lost. The adult organs such as antennae, wings and copulatory apparatus develop. The pupa finally metamorphoses into the imago or adult in about 2-3 weeks time.

Imago or Adult:

The adult moth emerges out through an opening at the end of the cocoon in about 2 to 3 weeks time, if allowed to live. Immediately before emergence, the pupa secretes an alkaline fluid, that softens one end of the cocoon and after breaking its silk strands, a feeble crumpled adult squeezes its way out. Soon after emergence, the adult silk moths mate, lay eggs and die.

Economic Importance of Mulberry Silkworm:

The mulberry silkworm moth is a very useful and valuable insect. It provides two very important products such as silk and gut to the mankind.

1. Silk:

The true silk of commerce is the secretion of the caterpillars of silkworm moth. Silk is a secretion in the form of fine threads, produced by caterpillars in preparing cocoons for their pupae. Long sac-like silk- glands, which are, in fact, modified salivary glands, secrete a thick pasty substance, which is passed out through a pair of fine ducts that open on the lower lip.

This secretion is spun by the caterpillar into fine threads which harden on exposure to air to form fairly strong and pliable silk-strands. The caterpillar larva prepares silk filaments several thousand metre in length at the rate of 15.00 cm per minute.

2. Gut:

Another economic value of the silkworm is the preparation of gut used for surgical and fishing purposes. For preparing the gut, the intestines of silkworms are extracted, made into strings, dried, treated and packed. This industry has good prospects and is growing in Italy, Spain, Formosa, Japan and India.

Diseases in Silkworms:

Silkworms suffer form several diseases. Chief of these is pebrine caused by a protozoan parasite Nosema bombycis of the microsporidian group.

In this disease the caterpillars turn pale brown and later on shrink and die. This disease is highly infectious, transmittable through eggs and responsible for very heavy economic losses. The control is brought about by a microscopic examination of the body fluids of the female, in which the parasites (pebrine corpuscles) are met with.

The eggs may be discarded or retained according to the presence or absence of parasites. Other diseases are fletcherie and grasserie but of minor importance. Sometimes caterpillars exhibit symptoms like jaundice disease, i.e., losing appetite, showing irregular growths, etc.

Other Silkworm Moths:

There are two other silkworm moths which also yield silk. These are Attacus receni, B, the Eri silkworm moth and Antherea paphia, B, the tassar silkworm moth. Both these moths belong to the family Saturnidae are large-sized and their caterpillars are also considerably monstrous, stout and about 10.00 cm long.

The Eri silkworm which lives upon castor, is a domesticated form, cultivated in warm damp places. It is found in South-East Asia. Its life history resembles that of the mulberry worm. Its cocoon has loose texture and silk is not reliable, hence, this is carded and spun. The gloss on the thread is inferior. Adults are stout dark moths with dark brown white spotted and striped wings.

The tassar silkworm resembles the Eri but the caterpillars feed upon Dalbergia, Shorea, and Terminalia, etc. The cocoon is hard shell-like of the size of a hen’s egg and is generally found attached to a plant by a stalk.

The moth has yellowish or deep brown wings with an eye-spot on each one. It is found in China, India and Sri Lanka. Cocoon has reelable silk. This is a wild variety but can be domesticated. The silk produced by Eri silkworm and tassar silkworm is not of very good quality.

Other silkworms, viz., Moon moth, Atlas moth, Cashew caterpillars and Ficus worm, although produce silk cocoons but the quality of filament produced is inferior and weak, hence, they have no economic value.

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Striking Facts About Silkworms

Silk, one of the most exotic fabrics is created by silkworms. This AnimalSake article is a compilation of some interesting silkworm facts.

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Silk, one of the most exotic fabrics is created by silkworms. This AnimalSake article is a compilation of some interesting silkworm facts.

Silkworms also known as domesticated silk moth and Bombyx Mori (‘Silkworm of the Mulberry Tree’ in Latin), is the insect from which silk is produced. One of the first products in the world to get the ‘Made in China’ tag is silk! Silk has been cultivated in China from ancient times and traded world wide ever since.

The biological classification of the silkworm is made as follows:

  • Kingdom: Animalia (as it is a multi-cellular eukaryotic organism)
  • Phylum: Arthropoda (as they are invertebrate organisms with appendages and exoskeleton)
  • Class: Insecta (as they have a three part body, compound eyes and antennae)
  • Order: Lepidoptera (as it undergoes complete metamorphosis, going through a four stage life cycle)
  • Family: Bombycidae (as it shows all the characteristics of the Moth family)
  • Genus: Bombyx (as it is a mulberry silk moth)

Silkworm Facts

These facts about silkworms are classified according to various points related to the silkworm’s life cycle, silkworm habitat and various uses of silkworms.

Life Cycle

The silkworm life cycle goes through the larva-cocoon-moth stages, which are typical of most moth-like insects. Here are some interesting facts about silkworms and their life cycle.

  • The silkworm eggs, laid out about 300 to 400 at a time, generally take about ten days to hatch. Once the eggs hatch, the larvae or bay silkworms eat incessantly and are always famished.
  • They prefer eating white mulberry tree leaves, as they have an attraction for the mulberry oderant called cis-jamone. They feed on all varieties of mulberry leaves.
  • The silkworm larvae shed their skin four times in a row. After the fourth shedding, the bodies of larvae turn slightly yellow and skin becomes tighter. This stage is the precursor of the ‘Cocoon’ stage.
  • The larvae go into the motionless pupal state, after enclosing themselves in an envelope of raw silk, produced by their salivary glands. It is in this stage that silk is extracted from them. If left undisturbed, the cocoon is eventually broken and a young adult moth emerges out of it.
  • If the raw silk of a single cocoon is unfolded, it will contain raw silk thread of about 300 to 900 meters in length. The raw silk fibers, which are about 10 micrometers in diameter are very lustrous and fine. To make one pound of silk, about 3000 cocoons are boiled in water. This kills the silkworms and makes the extraction of silk easier.
  • The adult silk moth cannot fly.

Here are some facts about the uses of silkworms.

  • The primary use of silkworms is in the production of silk. Every year, 70 million pounds of raw silk is produced, after about 10 billion pounds of mulberry trees are consumed by the silkworm larvae!
  • The length of the 70 million pound fabric can easily cover about 300 round trips to the Sun.
  • Silkworms are a part of cuisine in both Koreas and China. A snack food called beondegi, made from boiled and seasoned silkworm pupae is very popular. Chinese like eating roasted silkworm pupae.

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Different Types of Silk — And They Aren’t All From Worms!

Silk exudes elegance and sophistication at first glance. But what is it that makes silk so desirable? Is it the visual, attention-grabbing features — it’s shine and opulence? Is it the intricate way that it is manufactured? Is it the heritage dating back thousands of years? Is it purely the price tag? Whatever the reason, silk is a highly sought after commodity and consumers yearn for garments and soft furnishings made in silk.

You might not realise, but silk can be made from many varieties of silkworm — and sometimes no worms at all (as you’ll discover in a minute)! Whatever the source, these moths and worms produce a protein “fibroin” that is the main element in silk. Different types of silkworm will create fabrics with different characteristics. Here’s a little look at what you can expect from three main varieties of silkworm. and a few others!

Silk exudes elegance and sophistication. #Silk #production

Mulberry Silk — Bombyx Mori

Mulberry silk is the most common among the many kinds of silk. It makes up 90% of the silk supply in the world. This popular kind is produced by the bombyx mori silkworms which are fed from the mulberry bush (thus the name).

Since it is a common kind of silk, acquiring it is easy. Countries such as China, Japan and Korea have an abundance of it in particular. One of the disadvantages of using this kind of silk is that it needs special care to maintain it’s smooth texture. It also is often obtained in an unethical way, by killing the silkworms in their cocoons to extract the long fibres. For more information on this, have a look at our article The Pros and Cons of Silk Production, which also includes information on vegetarian silks, or ‘Peace Silks’.

Tussah Silk

Tussah silk is produced by tussah silkworms. Unlike other silks, this one has a distinct light golden to dark brown colour. This is a result of the tannin-rich leaves that tussah silkworms consume.

Silk is said to be one of the strongest fibres around — and it’s certainly the case with these thicker tussahs and makes it an ideal material for couches, jackets and sweaters.

Muga is akin to Tussah silk as the semi-domesticated silkworm Antheraea assamensis that produces it comes from the same family. Muga originates in India, and the silk it is known for its golden brown and glossy texture. Along with the Eri (below) and Pat silk, Muga silk is sometimes referred to as Assam silk, as fabrics produced from these silkworms were reserved for the exclusive use of royal families in Assam, India, for 600 years!

Muga production is considered more eco-friendly as the silkworm does not require delicate care. This makes it an affordable silk type too. Muga’s porosity can sometimes become a disadvantage as it limits the use of bleach (which for us more eco-conscious types, is an advantage!) but also means that it can’t be dyed.

Eri Silk

Eri silk is derived from the domesticated silkworm Philosamia rinini. It is a fine silk that is almost as white in colour as the Bombyx mori (Mulberry Silk we talked about above). Even though Eri is spun from the cocoons of domesticated silkworms, it is a “peace silk” because the silk caterpillars are not destroyed in the cocoon but are allowed to emerge as moths and live a full lifecycle. Because the cocoons are damaged when the moth emerges, Eri silk is spun rather than reeled. It usually has the matt appearance of wool or cotton, but the sheen and softness of silk and is commonly cultivated in India, Japan and China.

Aside from the Bombyx mori, this is the only other silkworm that is completely domesticated — so it relies on human intervention to be developed. And just like the Bombyx Mori, the name «Eri» is said to derive from the Assamese word «Era», which means castor plant — the food that the worms feed on.

This is a very durable silk and makes a great material for clothing, and surprisingly, soft furnishings such as curtains and couches. The only drawback of using such silk is the fact that it is heavy to wash. It may also harbor microorganisms as it is easier for them to stick on its thicker layers.

Mussel Silk

As the name implies, this silk is produced by mussels — yes, the same ones that can be found on seabeds. It is also sometimes called Sea Silk. This differs from the other silk types we’ve mentioned so far as it is not produced by silkworms.

I bet you didn’t know that this fabric has been produced since the Ancient Greeks were around — that’s as far back as the 8th century BC! If you like ‘unusual’, then this is it! It is difficult to source this kind of silk nowadays due to the effects of pollution on its source. Since its production is rare, it counts as one of the most expensive silks to date. The most common type of mussel, or more accurately mollusc used in the production is the Byssus, and this fabric tends to be called Byssus Cloth. There is an amazing explanation of the fabrics and the differences between them here.

Spider Silk

Like Mussel silk, you may be surprised to learn that spider silk has long been used by ancient cultures. But unlike other types of silk, this is the most difficult one to produce as spiders cannot just be bred like silkworms. Spiders cannot produce as much yarn as silkworms either.

But though the production of this type of silk may seem difficult, its output is certainly worth the effort. It is regarded as one of the most durable types of silk as it is now being utilised in the production of telescopes, bulletproof vests and wear-resistant clothing!

In June 2012 the world’s largest pieces of cloth made from spider silk went on public display for the first time. This included a brocaded shawl and a cape made from the silk of more than one million female golden orb-weaver spiders collected in the highlands of Madagascar. This video shows how the golden spider silk was collected, woven, embroidered and appliquéd to create both the shawl and cape that featured in this exhibition.

If you like these articles, then please sign up to our monthly newsletter, where I round up all the latest posts. You can tweet the article using the tweet buttons throughout the article and below.

Spider silk is one of the strongest #Spider Silk

Did you know mussels make silk? #Silk #Production #Mussels

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