This document provides information about silk production from silkworms. It discusses the different types of silkworms used for silk production, including the most common domesticated silkworm Bombyx mori. It describes the life cycle of the silkworm from egg to adult moth and the process of silk production, where silkworm larvae spin cocoons made of silk fiber. It also gives an overview of the sericulture industry and management processes involved in commercial silk production.

1. SILK MOTH AND SILK
PRODUCTION
Subham Preetam
Master in Biotechnology
Email Id: sspritamrath93@gmail.com
Linked in :- www.linkedin.com/in/subham-preetam-97b2b0148
Reserchgate ID:- https://www.researchgate.net/profile/Subham_Preetam2

3. I/NTRODUCTION
Silk fire is protein produced from the silk glands of silkworms.
The technique of silk production is known as sericulture. It is an
agro industry and is playing an important role in the economic
development of silk rearing pockets of rural India providing
gainful occupation to 64 lakh persons. One hectare of Mulberry
generates employment of about 12 man years and family
members ranging in age between 18 to 60 years can engage
themselves in various sericulture activities, such as, cultivation of
food plants (Mulberry, castor etc., silkworm rearing, egg
production, silk reeling, weaving etc. India is the second largest
producer of silk in the world after China and has the distinction
of producing all the four types of silk i.e. (a) Mulberry silk
(91.7%); (b) Tasar silk (1.4%); (c) Eri silk (6.4%); and (d) Muga
silk (.5%) which are produced by different species of silkworms

4. TYPES OF SILKWORMS
A large number of wild and semi-domesticated silk-moths belong to
the family satumiidae. Many of them have been partly cultivated for
centuries to produce usable silk in oriental Asia.
 Muga silkworm :- (Antheraea assamentsis). It is a wild and
semidomesticated species in Assam, W.Bengal, Bihar and Orisa. Cocoons are
amber or white and the caterpillars feed on Machilus, cinnamon, etc.
 2. Tussore or Tassah Silkworm (Antheraea mylitta or A. paphia). It is found in
China, India, and Shri lanka, etc. its caterpillars feed on leaves of fig, oak, ber, sal,
etc. cocoons are brown, red or yellow and collected from forestes, as the moths
do not breed easily in captivity

5.  Oaksilkworm :- a. pernyi of china nand japan, a . roylei of
the Himalaya and a. yamamai of japan have been collected
and reared for centuries. They produce silk of a fine
quality.
 Giant silkworm :- Attacus atias of India and Malaysia, is
nearly the largest of all living insects reaching up to 28 cm
in wing span.
 Eri silkworm :- Attacus rechinii or phlosamia ricinii of S.E.
Asia, feeds on castor and produces a rough and strong silk
locally known as “Arandi silk”.

6. Chinese of mulberry silkworm :- The commonest of
all, which produces most of the raw silk we use, is
Bombyx mori. It belongs to ithe family Bombycidae.
It is found on mulberry leaves in india. Although a
native of china, it is almost universally
domesticated. It has been reared for so many
centuries that it no langer exists in a wild state. By
careful selextion and hybridization many races have
been developed to meet the various nees of
climate, quality and quantity of the silk obtained.
The silk obtained from this silkworm is white or
yellow in colour.

7. Habits and Habitat
Silkworm has been domesticated for so long that it can no longer
survive in nature without human care. The original stock probably no longer
exists. As a result of domestication for centuries and continued selection for
certain qualities, the present day silk moth is far from resembling its ancient
ancestors. The adult silk moths con no longer fly due to heavy body and
feeble wings. The larvae have lost the capacity to search food, and will
starve unless the food is placed right near them. They are reared in
domestication on a diet of mulberry leaves. But, the adult moth does not
feed during its short span of 4 to 5 days only. Commercial silk is secreted
by the silk glands of larvae.

8. External Features
Adult silk moth is a medium-sized insect, about 25 mm long and
with a wing span of 40-50 mm. body is robust, creamy-white or
yellow in colour, and divided into usual 3 regions: head, thorax and
abdomen. Head is small and bears a pair of compound eyes, a pair
of branched or plumed antennae, and degenerate siphoning mouth
parts. Thorax bears 3 pairs of small legs and 2 pairs of large but
feeble wings marked by several faint or brown lines. Entire body is
covered by minute coloured scales. Abdomen of female is larger and
much distended due to great number of eggs it contains.

9. Life History
Silkworm is dioecious, i.e., the sexes are separate.
Fertilization is internal, preceded by copulation. Development
includes a complicated metamorphosis.

11. Eggs :- Soon after fertilization, each female lays about 300-500
eggs in clusters upon the leaves of mulberry tree. Female covers
the eggs bya gelatinous secretion which sticks them to the leaves.
Small, smooth and spherical eggs are first yellowish white and
become darker later on. After laying, the female does not take
food and dies within 4-5 days.

12. 1. Caterpillar larva :- The larva which hatches from egg in about 10 days, is
known as the caterpillar. The 1st instar larva is a tiny creature,about 6 mm
long, and moves about in a characteristic looping manner. It has a rough and
wrinkled whitish or grayish body, which is made of 12 segments. Its head
bears mandibulate mouth parts with which it at-once starts feeding on
mulberry leaves and grown very quickly. It can also be fed on lettuce and
osage orange (maclura) leaves. After 4 or 5 days, it stops feeding and
becomes inactive. Moulting or ecdysis then takes place. Its older skin bursts
and a new caterpillar emerges out with a new skin and slightly bigger in size
than the older caterpillar. It resumes eating voraciously and growing until the
skin is again cast off after a week. The larva repeats this process four times.

13. Pupa :- Mature caterpillar stops feeding and returns to a corner among the leaves.
Its salivary glands now secrete a sticky fluid through a narrow pore of its spinning
apparatus, called spinneret, situated on hypopharynx. The sticky substance urns into
a fine, long and solid thread of silk in contact with air. Silk thread is made of 5
filaments stuck together by a gummy substance or sericin, which is secreted by two
other glands. It becomes wrapped around the body of caterpillar forming a pulal
case or covering known as cocoon. This process goes on for about 3-4 days, at the
end of which the silkworm is enclosed within a thick, oval, white or yellow silken
cocoon. A single caterpillar is said to produce nearly 1000-1500 meters of silk thread
in this manner. Within a fortnight the silkworm transforms inside, cocoon info a
tubular brownish organism, the pupa or chrysalis.

14. Imago :- A active metamorphic changes take place during pupation.
Unregimented abdominal prologs disappear, while thorax develops two
pairs of wings. The pupa finally metamorphoses into the baby insect or
imago. It secretes an alkaline fluid to moisten one end of cocoon and
then escapes by forcing its way out of the softened silk. Soon after
emergence the male and female moths mate, lay eggs and die within 3
to 4 days.

15. SILK PRODUCTION
Commercial silk is secreted by the silk glands (salivary glands)
of larval silkworms. The rearing of silkworms for the
production of raw silk is known as sericulture. It is an industry
in a few countries including India.
Historical:- Silk was manufactured for the first time probably
in China, about 3500 B.C It was introduced in Europe in 552
A.D. today, sericulture is an important industry of several
Asian and European countries, but China and Japan are the
only great producers of raw silk.

16. Sericulture industry (Management)
The major steps and requirements of sericulture industry are
briefly as follows :-
 Requirements and appliances :- The prime requirement for
commercial production of good silk, are genetically improved races of
Bombyx mori, keeping in view the climatic conditions of the region.
Another need of the industry is the plantation of good nutritive
varieties of mulberry for a continuous supply of their leaves for
feeding the larvae.

17.  Grainage management :- Maintenance of good quality races of
silkworms and the supply of good quality seeds to readers is known
as grain age management. Soon after emergence, the males and
females are segregated before they can mate. Females of one lot are
later kept with males of another lot for mating and they die soon
after laying eggs. The eggs, now known as “seeds” are kept in
sterilized trays at 4 c and moved periodically with feather to ensure
100 per cent hatching. The seeds are kept in diapauses and their
hatching time is artificially coincided with the best season of
mulberry. The readers are provided with either seeds or the 2nd
instars larvae, depending on their knowledge and managing capacity
for obtaining good quality cocoons.

18. Stiffing.:- For obtaining the commercial silk the cocoons are treated
with hot water or placed in a hot oven to kill the pupae inside. If allowed
to hatch, they would cut the silk threads in emerging. This process of
killing the cocoons is called stifling in the industry.

19. Reeling and spinning. :- Removal of silk thread from cocoons is termed reeling.
After boiling, the cocoons become soft and their fibre become loose so that
they can be easily unwoven or reeled off. Each cocoon is made of a single fibre.
A single cocoon yields 1,000 to 1,500 meters of unbroken silk fibre. 454 gm of
silk is obtained from about 25,000 cocoons. A few alive cocoons are kept as
“seeds” for the next crop.
4 or 5 silk fibers are passed through eyelets of wooden guides and
twisted into one thread. It is wound round a large wheel and later transferred
to spools. This is called raw silk or reeled silk. For achieving its characteristic
luster, raw silk is again boiled, purified by acid or by fermentation, and
thoroughly washed. Several such silk threads are twisted to get fibre silk,
through the process known as spinning. The damaged cocoons and waste
treads are also teased and spun into threads, called spun silk.

21. Diseases of silkworm :- The caterpillars of silkworm are subject to a
severe hereditary disease, known as pebrine. It is caused by a protozoan
parasite (Nosema bombycis) which is transmitted through the eggs. The
examination of the blood of females and avoiding the eggs containing
the parasite. Caterpillars are also subject to parasitism by certain tachina
flies, which lay their eggs upon mulberry leaves and thus get inside the
body of caterpillars through their alimentary canal.

22. Sericulture in india
Sericulture is unique and profitable in many ways, in india. It provides
larger opportunities to unskilled labor at the minimum cost.l Even the
old and handicapped members of a family can be employed gainfully. It
requires a small capital investment of a few hundred rupees and the
returns are quick and adequate.

23. Besides India, other natural silk producing countries are japan, china, south
korea and U.S.S.R.india is the onlycountry producing all the four commercial
varieties of natural silk.
 Production of mulberrysilk is confined to karnatak, west Bengal, jammu and
Kashmir, Andhra Pradesh and tamil nadu. India is fifth in the world
production of mulberry silk.
 The major tasar silk producing centres are in Bihar, Madhya Pradesh, Orissa
and west Bengal. India is second in the world production of tasar silk.
 The bulk of eri silk is produced in Assam which also holds the virtual
monopoly over the world muga silk production.
 The states of Manipur, assam, Nagaland, uttar Pradesh, arunachal Pradesh,
Meghalaya and Mizoram are producing a new variety of tassar known as
oak tassar

24. Problems :- At present, the Indian silk industry faces many problems of
productivity, marketing and finance. Per hectare yield and quality of raw
silk are poor in comparison to other major silk producing countries. The
central silk research institute, Mysore is dealing with these problems,.
The Karnataka Government has also taken various steps to improve silk
production and quality.

25. Silk has following peculiar properties: -
 Natural colour of Mulberry silk is white , yellow or yellowish green; that of
Tasar brown; of Muga, light brown or golden; and of Eri, brick red or creamy
white or light brown.
 Silk has all desirable qualities of textile fibres, viz. strength, elasticity,
softness, coolness, and affinity to dyes. The silk fibre is exceptionally strong
having a breaking strength of 65,000-lbs/sq. inch.
 Silk fibre can elongate 20% of original length before breaking.
 Density is 1.3-1.37g/cm3.
 Natural silk is hygroscopic and gains moisture up to 11%.
 Silk is poor conductor of heat and electricity. However, under friction, it
produces static electricity. Silk is sensitive to light and UV- rays

26. . Use of silk:
 Silk is used in the manufacture of following articles:
 Garments in various weaves like plain, crepe, georgette and velvet.
 Knitted goods such as vests, gloves, socks, stockings.
 Silk is dyed and printed to prepare ornamented fabrics for saries, ghagras, lehengas and dupattas.
 Jackets, shawls and wrappers.
 Caps, handkerchiefs, scarves, dhotis, turbans.
 Quilts, bedcovers, cushions, table-cloths and curtains generally from Eri-silk or spun silk.
 Parachutes and parachute cords.
 Fishing lines.
 Sieve for flour mills.
 insulation coil for electric and telephone wire.
 Tyres of racing cars.
 Artillery gunpowder.
 Surgical sutures.

27. THANKS AND REGARDS
SUBHAM PREETAM
BIOTECHNOLOGIST, ITER, SOA UNIVERSITY