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THEORETICAL BASES OF NATURAL SCIENCE EDUCATION-II

ONLINE ASSIGNMENT

TOPIC : SERICULTURE

SUBMITTED TO:

ANUJA V S.

Lectr. Natural Science

KUCTE Anchal

SUBMITTED BY:

ABHILASH P M

REG: NO:13975001

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INDEX

Sl. No Content Page No

1 Introduction 3

2 Sericulture 4

3 Types of Silkworm 5

4 Silk 8

5 Rearing of Silkworm 9

6 Mounting 12

5 Conclusion 14

6 Reference 15

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INTRODUCTION

Sericulture is the production of raw silk by raising silk worms. The productivity

and profitability of sericulture depends on the yield of mulberry crop. It is a cottage industry

combining agriculture and industry. The end product of this agro-industry is silk. The

production process of silk involves a long chain of interdependent specialized operations such

as mulburry cultivation, silkworm seed production, rearing of silk worm, reeling, twisting and

weaving of silk, etc. which provide employment to about 60 lakhs people in the villages of

India through family labour and is the second largest employer in the country. Sericulture is

an export oriented agro - industry. Indian silks are exported to more than 50 countries and

gains about 800 crores of rupees each year from it. We have a unique position among the silk

producing countries, because India is the only country in the world producing all the four

commercially important varieties of natural silk - Mulberry, Tasar, Eri, and Muga silk.

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DATACOLLECTION

SERICULTURE

Sericulture is the production of raw silk by raising silk worms. The productivity

and profitability of sericulture depends on the yield of mulberry crop. It is a cottage industry

combining agriculture and industry. The end product of this agro-industry is silk. The

production process of silk involves a long chain of interdependent specialized operations such

as mulburry cultivation, silkworm seed production, rearing of silk worm, reeling, twisting and

weaving of silk, etc. which provide employment to about 60 lakhs people in the villages of

India through family labour and is the second largest employer in the country. Sericulture is

an export oriented agro - industry. Indian silks are exported to more than 50 countries and

gains about 800 crores of rupees each year from it. We have a unique position among the silk

producing countries, because India is the only country in the world producing all the four

commercially important varieties of natural silk - Mulberry, Tasar, Eri, and Muga silk.

The silk industry originated in China and was kept in secret by them for about 3000

years. The sericulture industry is well established in India since the 4th century. Major silk

producing states in India are Karnataka, Andhra Pradesh, Tamil Nadu and West Bengal. Only

recently Kerala has got a place in the sericulture map of India.The scope and potentiality of

sericulture industry is not limited in the production of silk as a textile fibre. The silk fibre

produced by the mulberry silkworm and its byproducts can be utilized for many other

purposes. The special properties of silk fibre makes it a raw material for making electric

insulations, tyre linings, artificial blood vessels, surgical sutures, etc. Hydrolized proteins,

aminoacids and vit B? (Riboflavin) are extracted from the silkworm pupa. The major by

products in sericulture industry are rearing wastes, waste cocoons and silkworm faeces.

Rearing wastes can be used for the production of biogas and vermicompost. Waste cocoons

are the raw material of cocoon handicraft which involve the production of garlands; flowers,

dolls, greeting cards etc. Chlorophyll and phytol can be extracted from the silkworm faeces.

Phytol is a raw mater \\ for manufacturing vitamin E and K. The faeces is also used in plastic

industry and as feed for fish, pig, cattle, etc. All these sideline developments of sericulture

provide further employment opportunities and economic growth.

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TYPES OF SILKWORMS

There are four kinds of silk worms which are producing commercially important natural

silk. They are the following :

Mulberry silkworm

It is a domesticated variety of silkworm and has been exploited for over 4000 years. All

the strains of mulberry silkworm belong to the species Bombyx mori. The term silk generally

refers to the silk of mulberry silkworm because it contributes about 95 percent of world's silk

production. Bombyx mori produces cocoons with continuous silk filament and therefore, it

can be industrially reeled to produce raw silk.

Eri silkworm

It is a domesticated species and is reared on castor plants, so they are called castor

silkworms. The castor silkworm belongs ,to the species Sarnia cynthia ricini. (Philosamia

ricini) Eri silkworms produce a white or brick red silk known as Eri silk or Endi or Errandi

silk. The silk filament produced by these worms is not continuous and uniform and cannot be

reeled properly. So the moths are allowed to emerge from the cocoons in natural way and the

pierced cocoons are used to produce Eri silk. In India, Assam is the home of the Eri silk

industry.

Tasar silkworm

Antheraea myletta is the taser silkworm. It is bivoltine species having two crops in a year.

Indian taser worm feeds on the leaves of Terminalia and other minor host plants. The

cocoons are very hard because of a hard protective covering secreted by the worms. The

cocoons can be reeled into raw silk like mulberry silkworm cocoons. The reeling mechanism

is slightly different from mulberry silk cocoons. The hard protective covering must be

softened before reeling, using certain special technique.

Muga silkworm

Muga silkworms belong to the species, Antheraea assamensis. These worms produce

strong and beautiful golden yellow silk threads. These are found only in Assam. The worms

feed on the leaves of som and soalu and Indian enjoys the sole monopoly in the production of

muga silk in the world.

Life cycle of Bombyx mori

Life cycle of mulberry silk worm involves four distinct stages, viz. egg, larva, pupa and

adult. The duration of life cycle may vary from six to eight weeks depending on racial

characteristics and climatic conditions. Multivoltine races in tropical areas have the shortest

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life cycle. So silkworm rearing is continuous in tropical areas whereas in sub-tropical and

temperate areas it is seasonal.

Egg. Each female lays about 400 eggs in clusters up on the mulberry leaves. The eggs are

tiny smooth and ovoid. The colour of the eggs may vary from white, yellow or brown,

depending on the races. Around 2000 eggs weighs to a gramme. The female dies within four

to five days. Larva. After 9 to 12 days the silk worm hatches from the egg. The newly

hatched larva is black or dark brown in colour. It has a large head and the body is covered

with dense black bristles and looks like black ants. So they are generally refered to as “ants”

or “ant worms”. The body of the larva has 13 visible segments and is divisible into head,

thorax and abdomen.

The head consists of six body segments, which are fused together. It is provided with a

pair of five jointed antennae which are sensory in function. Six pairs of light sensitive ocelli

are present at the base of the antenna. Mouth parts consist of mandibles, maxillae and labium.

The mandibles are adapted for mastication. The maxillae are used to detect the taste of food.

The labium has a chitinized prementum which carries a median process, a spinneret through

which silk is secreted from the silk gland. The labial plaps are present on either sides of the

spinneret.

The thorax consists of three segments. Each thoracic segment carries a pair of three jointed

legs with distal sharp claws. All the larvae carry the charactristic larval markings called eye

spots on the dorsal side of the mesothorax.

The abdomen consists of eleven segments, although only nine can be distinguished

because the last three segments are fused together to form the nineth segment, anal piate and

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a pair of caudal legs. In addition to the caudal legs, the abdomen is provided with four pairs

of legs. All the five pairs of abdominal legs are fleshy unsegmented muscular protuberances

called prolegs or pseudolegs. A short anal horn is present on the 8th segment.

The larval life lasts for 25 to 30 days. This is the most active period in the life cycle of

Bombyx mori. The larva fees voraciously upon the mulberry leaves and grows very quickly

about 10000 times its weight at the time of hatching. During the larval life the worms moult

four times. The four larval moults divide the larval life into five instars which are commonly

referred to as five different ages or stages. The first three instars constitute the “young age"

and the last two instarthe “late age". Prior to each moylt, the larva stops its feeding and rest

with its head held up. This resting for moulting is generally refered to as “going to sleep” and

the emergence of the worm from the mouft as “waking up”.

Pupa.

At the end of fifth instar the caterpillar stops feeding and begins to secrete a sticky fluid, from

the silk gland through a narrow pore called spinneret. The sticky substance turns into a fine

long ahd solid thread erf silk in the air. This thread is used for sp mning the pupal case or

cocoon. A mature worm completes spinning of cocoon in 48 to 72 hrs. During the pupal

period the larval body and its internal organs undergo changes and assumes the new form of

adult moth. The pupal life may lasts 8 to 14 days. At the end of pupal period the adult moth

pierces the fibrous cocoon with the aid of the alkaline salivary secretion.

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What is Silk?

Silk is a fibrous protein produced by the silkworm for spinning cocoon. This cocoon provides

protection to the soft delicate worm during its pupal life. Silk is secreted as a fluid which

turns into a fine long solid thread in the air. Silk is a long filament composed of two proteins -

fibroin or real silk which constitutes the core of the filament and sercin or gum stuff which is

a waxy substance around the fibroin. The secretion of the silk filament is continuous ranging

from 350 meters to 1800 meters or more. Commercial silk is obtained from reeling of

cocoons. Reeling is the unwinding of the silk filament from the cocoon after killing the pupa.

Adult. The adult moth emerging from the pupa is not able to fly because of its domestication

for more than four thousand years. It does not feed during its adult life. The adult life is short

ranging from 3 to 10 days depending upon races and seasons. The body of the moth is

divisible into head, thorax, and abdomen. The body surface is covered with scales.

The silkworm moth is dioecious i.e. the sexes are separate. Fertilization is internal.

Immediatly after emerging from the pupa the moths mate, lay eggs, and die.

Adult.

The adult moth emerging from the pupa is not able to fly because of its domestication for

more than four thousand years. It does not feed during its adult life. The adult life is short

ranging from 3 to 10 days depending upon races and seasons. The body of the moth is

divisible into head, thorax, and abdomen. The body surface is covered with scales.

The silkworm moth is dioecious i.e. the sexes are separate. Fertilization is internal.

Immediatly after emerging from the pupa the moths mate, lay eggs, and die.

The purpose of silkworm rearing is to produce cocoons for raw silk or for the silkworm

seed production. This process requires the production of mulberry leaves for feeding the

silkworms. Larva of Bombyx moriis very delicate and shows a rapid rate of growth within a

short period of time. The larva, when it hatches from the egg is about 0.4 mg. attains weight

around 5 gm within a period of four weeks and pupate. Slight variation in the environmental

conditions especially temperature and humidity may violently affects this delicate creature. It

is also susceptible to a number of diseases which may cause heavy loss of the crop. The

young and late age larvae behave differently during rearing, in relation to leaf quality and

environmental conditions. So foreach instqrthey require different techniques. These facts

show that the silkworm rearing is a highly skilled job which needs some technical

knowledge. The following are the various technical aspects of silkworm rearing.

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REARING

Rearing house

Silkworm rearing requires certain specified environmental conditions like temperature,

humidity, air and light. The rearing houses are planned and constructed to provide optimum

environmental conditions to ensure good quality of cocoons. Enough space must be. 38

available to carry out leaf preservation young age rearing, late age rearing and mounting.

There should be fecilities to conduct effective disinfection.

Leaf feeding

The larvae of Bombyx mori is monophagous, feeding exclusively on mulberry leaves. The

success of silkworm crop depends on the sufficient supply of good and suitable quality of

mulburry leaves. Leaf 40 quality determines the quality of cocoon. The leaf quality depends

on various factors such as the variety of mulberry plant, soil, pruning, fertilizers, rain fall,

irrigation, leaf maturity, sasons, etc.

The quality of leaf required for the young age differs from those of late age. During young

age the larva requires tender soft and sacculent leaves having higher moisture and protein and

less starch and fibres. The late age worms require soft and mature leaves having high protein

content and not too much moisture. Over matured leaves, contain less moisture and more

starch and fibres, are not suitable for both young age and late age.

For collecting the correct leaves forfeeding the worms, the „largest glossy leaf method‟ is

adopted. The largest glossy leaf is the full blown largest leaf among the first few leaves on

the top of the shoot. Five or six leaves from the one below the largest giossy leaf is suitable

for feeding first instar larvae. Next 4 or 5 leaves used for second instar and all the tender

leaves below it, upto 13th or 15th leaf from the first glossy, used for third instars. The

remaining, thick, slow wilt leaves have higher protein content and not contain too much water

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is fit for fourth and fifth instars. Leaves from less than 28 days old bush or more than 70 days

old bush is not desirable forfeeding. The nutrition value of mulburry leaf increases with the

position as it goes up from bottom to top.

The leaves are harvested early in.the morning or late in the evening, i.e., the cool hours of

the day, to retain their freshness and sacculence, which give better edibility of the leaves. The

leaves harvested should be preserved in a moist cool and clean place. In tropical areas like

India, leaves preserved loose under a wet cloth in a cool room with periodical sprinkling of

water will remain fresh and sacculent for longer time.

Feeding method.

Cut leaf feeding is the traditional practice and the leaves are chopped finely. Chopping of

leaves into too smaller fragments leads to quick drying up of the leaves and consequently

unfit for feeding the worms. So the leaves are not cut too finely even forthe feeding of the

first instar larva. Therefore, the leaves should be cut to optimum size at each stage of the

larva. The chopping of the leaves should be as given in the table. General practice is to give

four feeds per day at equal intervals.

The quantity of leaf required for each instar is different. So care should be taken to give

sufficient quantity of leaves for each stage of larval development. If feedings are insufficient,

this results in irregular growth and poor cocoon crop. The young age larvae show this

irregularity at high level due to poor nutrition. The feeding amount increases abruptly from

the 3rd instar larva.

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Rearing of young age - silkworms or Chawki

The larval life of the silkworm consists of five instars. The first two instars form the young

age or chawki and the last two instars form the late age. The third instar represents an

intermediate stage and is more closerto young age for their food and environmental

requiremnts.

Bamboo tray rearing

Wooden tray rearing

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MOUNTING OF WORMS

The process of transfer of fully mature or ripe worms to the suitable mountages from

the rearing bed is called mounting. Mountages or cocooning frames are certain devises or

contrivences which give support to the worms for the spinning of cocoons. At the end of

larval life the following sigins of maturity are shown by the larvae. They stop feeding, their

stomachs appear as empty. Larvae become translucent and yellow. Active raising of head is

another feature. Worms move towards the periphery of rearing tray. At the end of fifth instar

the silk worms stop feeding and show signs of maturity and get ready for pupation. After the

fourth moult the worms take six or seven days to reach maturity. The worms which show

signs of maturity should be picked up in time and mounted. A skilled rearer can identify the

suitable time for mounting.

Collecting and mounting worms require a lot of work. Generally the mature worms are

collected in hand trays and later mounted on suitable mountages by skilled labourers. The

most popular form of mouniage in India is Chandrika. Mounting of worms should be done in

v itilated room, at a rate of forty to fifty worms per sq. feet. This helps to obtain superior

quality cocoons.

Chandrika

Chandrika is made of bamboo. It consists of a rectangular mat having the size 1.8 x 1.2 m.

A spiral of bamboo tape about 5 cm broad fixed on the mat leaving a space about 5 cm

between the spirals. Chandrika provides all the advantages of a good mountage. There is

sufficient space for spinning cocoons so prevents the formation of double cocoons to a

minimum. It allows free circulation of air. So the excreta of the worms dry up quickly and do

not remain to stain the cocoons. It is easily available from the villages where bamboo

weaving industry is common. It can be easily transported and stored. The mountages can be

used again and again.

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Method of mounting

Hand picking.

The mature worms are separated from the rearing bed by hand picking and collected in a

small tray. These worms are immediately transferred on to suitable mountages. It is labour

consuming process and expensive.

Mounting by shaking.

To collect worms from the rearing bed, place branches of green leaves or

spread a net over it. Since the silk worms have a natural tendency of moving upwards, they

crawl on to the leaves or the nets. Then branches or nets are taken out and shaken over a mat

to detach the worms from it. These worms are collected and mounted on suitable mountages.

Self mounting. Bottle brush type of mountages are used for this method. The mountages are

placed directly on the rearing bed and the worms naturaly crowl up to the mountages and

pupate. Straw mountages are also used for self mounting. When sufficient number of larvae

reach the mountage it should be replaced by a new one. This method save much labour and

expenses for mounting. It is applicable, only if the larvae are uniformly mufured and also

difficult to get the appropriate density of the larvae on mountages.

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CONCLUSION

Sericulture biologically means that the cultivation of silkworm. Mulberry plants are

typically used as cultivating plant. Bombix mori is the most important silkworm. Sericulture

is the production of raw silk by raising silk worms. The productivity and profitability of

sericulture depends on the yield of mulberry crop. It is a cottage industry combining

agriculture and industry. The end product of this agro-industry is silk. The production process

of silk involves a long chain of interdependent specialized operations such as mulburry

cultivation, silkworm seed production, rearing of silk worm, reeling, twisting and weaving of

silk, etc. which provide employment to about 60 lakhs people in the villages of India through

family labour and is the second largest employer in the country. Sericulture is an export

oriented agro - industry. Indian silks are exported to more than 50 countries and gains about

800 crores of rupees each year from it. We have a unique position among the silk producing

countries, because India is the only country in the world producing all the four commercially

important varieties of natural silk - Mulberry, Tasar, Eri, and Muga silk.

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REFERENCE

Applied zoology - Zoological Society study material series

Ecology and Environmental biology ,Eugine P Oudum

SCERT Biology Textbook-2011 Edition