What is Silk Worm and its types?

2. Silkworm

3. Introduction
 silkworm (Bombyx mori) belong to family Bombycidae and
order Lepidoptera.
 They produce silk by feeding on mulberry plants.
 The larvae of silkworms feed on mulberry leaves.
 They become pupae and form a silky cocoon on pupal
body produced by the saliva from their mouth parts.
 When these cocoons are put in hot water and the threads
of silk appear clearly.
 Those threads are rolled and used for commercial
purpose.
 The silkworm industry is called as sericulture.

4. Larva Cacoon Adult

5. TYPES
 Silkworms can be categorized into three major groups:
 Univoltine
 Bivoltine
 Polyvoltine

6. Univoltine
 Single generation per year.
 This breed is generally linked with the geographical area
within greater Europe.
 The eggs of this breed hibernate during winter due to the
cold climate, and cross-fertilize only by spring,

7. Bivoltine
 Generally found in China, Japan, and Korea.
 The larval duration is short.
 The quality of the cocoons inferior to that of Univoltine
races.
 The breeding process of this type takes place twice
annually.

8. Polyvoltine
 Can only be found in the tropics.
 The eggs are laid by female moths and hatch within nine
to 12 days.
 The larval duration is short.
 The filament is fine and clean with little lousiness; but
with more lustrous.
 They produce more than 5-6 generations/year.

9. PROCESS OF SILK SYNTHESIS:
 Eggs take about 14 days to hatch into larvae, which eat
continuously.
 They are covered with tiny black hairs.
 When the color of their heads turns darker, it indicates
they are about to molt.
 After molting, the instar phase of the silkworms emerge
white, naked, and with little horns on their backs.

10.  After they have molted four times, their bodies become slightly yellow and
the skin becomes tighter.
 larvae then prepare to enter the pupal phase of their lifecycle, and enclose
themselves in a cocoon made up of raw silk produced by the salivary glands.
 The final molt from larva to pupa takes place within the cocoon.
 The moth – the adult phase of the lifecycle – is not capable of functional
flight.
 Silk moths have a wingspan of 3–5 cm (1.2–2.0 in) and a white, hairy body.
 Females are about two to three times bulkier than males (for they are
carrying many eggs), but are similarly colored.
 Adult Bombycidae have reduced mouth parts and do not feed, though a
human caretaker can feed them.

11. COCOON
 Cocoon is made of a thread of raw silk from 300 to about 900 m
(1,000 to 3,000 ft.) long.
 The fibers are very fine and lustrous, about 10 μm (0.0004 in) in
diameter.
 About 2,000 to 3,000 cocoons are required to make a pound of silk
(0.4 kg).
 At least 70 million pounds of raw silk are produced each year,
requiring nearly 10 billion cocoons.