2. INTRODUCTION:
Silkworms are the larva of adult moths. There are many types of silkworm but the
most commonly used and studied is the ‘Bombyx mori’ .The commercially bred
caterpillar of the domesticated silk moth Bombyx mori , which spins a cocoon
around itself that is later processed to yield silk fibre.
Legend has it that humans and silkworms met one fine morning in the year2640 B.C.
A Chinese Empress named Hsi-Ling-Chi (various other spellings found) was strolling
in her garden drinking tea when a white cocoon plopped into her cup from an
overhead tree.
It probably looked something like this:
3. Instead of dumping it out and asking her servant for another cup
of tea like any reasonable person would probably have done, she
studied the cocoon. She stirred the warm tea with her finger and
noticed a fine strand beginning to unravel from the fuzzy
cocoon. Being a weaver, she thought of using the fiber to make
cloth. She called to her servant and together they unwound the
cocoon into a single long filament. Thus, the silk industry was
born.
5. EGG:
It is the first stage of a silkworm’s life .
Female lays about300 - 400 eggs
Eggs stick to leaves with gelatinous secretion
Creamy yellow first, after few days they change into gray
In about18°C to 25°C larva hatches within 10 to 12 days.
Egg laying is completed in 1-24 hours.
6. LARVA (silkworm):
After hatching the larva is extremely hairy .
It feeds on mulberry leaves and grow very quickly.
After four to five days it becomes inactive.
Goes through five growth stages called ‘Instars’.
First instar molts. Such molting occurs four times
The enzyme secreted by the silk gland comes on contact with air and
becomes a hard and fine thread which is known as silk.
The larval stage lasts about 27 days
7. PUPA(cocoon):
The stage in which the larva undergoes active changes
called metamorphosis.
Colour can range from white to golden yellow.
Second molting occurs inside the cocoon.
Silk is obtained from the cocoon of the.
The cooked PUPAS are eaten and in some countries.
The cocoon takes about 2 - 3 weeks for to metamorphose
into adult
8. 14 days hatches inside the cocoon from its pupaskin
The adult silkworm is a.k.a a moth , are unisexual .
Once out the moth dries its wings and finds a mate (or vice-versa as is
often the case!),
Females have enlarged abdomens(as their abdomens are full of
unfertilized eggs)
Males are smaller, flutter a lot and bend the end of their abdomens
Fluttering behavior of males is their way to attract the females.
Male dies after copulation ,female is oviparous and dies after laying
eggs.
In this way silkworm completes its life cycle in 45 - 50 days .
Adult:LARVA
9. Economic Importance:
The silkworm industry bakes or boils the cocoon to kill the pupa, then
each cocoon is reeled. This is when one continuous strand of silk is
unwound from each cocoon, either by hand or by a machine. 6-8 of
these strands are twisted together to create one thread of silk.
Silk is a expensive product today . The cocoons of a silkworms is
made up of the enzyme secreted by the silk glands of a silkworm
which then turns into fine threads of silk . A single cocoon gives
about 1000 m of silk . Silk is a multimillion dollar business and
one of the most important exports from Asia. So many
people rear silkworms for a economical benefit . Many big
industries rear silkworms and are based on them for
income. The art of rearing silkworm for commercial
benefit is called ‘Sericulture’ . It cannot be
overstated in its importance to commerce,
industry and fashion
10. Some facts about silk and silkworms
- In almost 2 days a silkworm spins a single silk thread that is about 1,000 to 3,000 feet
long.
-The silkworm female deposits around 400 eggs at a time.
- The Silkworm (Bombyx mori) Latin for “silkworm of the mulberry tree") is, technically, not a
worm. It is
the larva or caterpillar of a moth in the family Bombicidae
-Strong as steel in tensile strength, silk is the strongest natural fiber known to man
-The shimmering appearance for which silk is prized comes from the fiber’s triangular prism-like
structure which allows silk cloth to refract incoming light at different angles
-A highly versatile fabric, silk has proven to be ideal for a variety of uses – from formal wear
to sleepwear, from parachutes to rugs, from medical sutures to prosthetic arteries.
-Silkworms are no longer found in the wild.
- For the business of silk the ancient Chinese had built a road through
the regions of Asia which was known as ‘silk road’.
11. Acknowledgement
I would like to acknowledge the efforts put in by our teachers for making our
weekends productive and enhancing our knowledge . Our special thanks to MR.
Suresh SIR Chaudhary for givining us an opportunity to make and present this
presentation . And lastly we would like to thank the websites and the person who
published our science book without which we could not have had completed the
project .
