Rearing of silkworms and production of commercially valuable silk is called sericulture.
All silkworms are moths belonging to the order Lepidoptera and superfamily Bombycoidae. The mulberry silkworm, Bombyx mori belongs to the family Saturniidae such as tasar silkworm (Antheraea mylitta), eri silkworm (Samia Cynthia ricini) and muga silkworm (Antheraea assama).
ECONOMIC IMPORTANCE
1. Silk is the queen of fiber, which is preferred by the people for its beauty, colour and comfort. Silk is universally world top fashion designated. Japanese use silk for making their national dresses Kimono.
2. Silk fiber is used for water absoption, dyeing, thermo tolerance, insulation and lusture. Raw silk is used for parachute, tire lining, electric insulator, artificial blood vessels and surgical sutures.
3. Silkworm pupae is used for oil extraction, protein extraction, amino acid and Vitamin B2 preparation. Diseased(muscardine) silkworm larvae and pupae are used for vitamin E preparation.
4. Sericulture provides employment to unemployed manpower in the country.
LIFE CYCLE OF SILKWORM
Mulberry silkworm is a completely domesticated insect which is never found wild. Some topographic species of this worm have been developed through differentiation, selection and feeding. On the basis of generation produced per year, three distinct groups viz univoltine (one generation per year), bivoltine (two generations per year) and multivoltine (many generations per year) are being recognized. The mulberry silkworm passes through complete metamorphosis, producing four distinct stages:-
1. Egg: Univoltine race deposits eggs in spring which undergo diapauses and hatch out only in next spring. Multivoltine race deposits eggs in non-hibernating eggs and produce 2-7 geberations in a year. The eggs are laid in clusters on the surface of the mulberry leaf or artificially prepared butter cups. A female lays eggs about 400-500 eggs popularly called as silk seeds. The eggs are small, oval in shape and creamy white in colour. At the time of hatching, they turn black and hatch in 9-11 days.
2. Larvae: Newly hatched larvae are tiny, 3 cm cylindrical in shape and black or dark in color. They become lighter and smoother during different succeeding instars. There are five larval instars - first three are known as young worms and rest two instars are called as grown up worms. The tiny caterpillar immediately after hatching begins to feed on mulberry leaves and grow rapidly. They molt d 5 times to reach maturity. After the last molt, larvae raise their head and search shelter for resting. They secrete silken thread and cover themselves. The larval stage lasts for 18 - 24 days.
3. Pupa: Full grown larvae begin to spin their cocoons. This takes about 3 days of constant motion of the head from side to side at the rate of 65 a minute. Larvae extrude a fine filament of pulpy material (brin or fibroin) through the silk glands. These are stuck together by sericin or silk gum in the spinneret to form a single continuous fiber of about 500 mm long and 0.02 mm diameter. The cocoon is oval in shape and white or yellow in color. After completing the process of silk secretion, the larva pupates inside the cocoon which provides protection for the developing pupa. The pupa is reddish brown in color. This stage lasts 11 - 14 days.
4. Adults: Adults come out by making a small hole through the cocoon. It is creamy white in color and measures 30 mm with a wing span of 40-50 mm. Female is bigger than male. They mate immediately after the emergence, do not take food and survive only for 2 - 3 days. The empty cocoons (after adult emergence) are called pierce cocoon. They are of low value because of staining and unreel ability into continuous threads.
All silkworms are moths belonging to the order Lepidoptera and superfamily Bombycoidae. The mulberry silkworm, Bombyx mori belongs to the family Saturniidae such as tasar silkworm (Antheraea mylitta), eri silkworm (Samia Cynthia ricini) and muga silkworm (Antheraea assama).
ECONOMIC IMPORTANCE
1. Silk is the queen of fiber, which is preferred by the people for its beauty, colour and comfort. Silk is universally world top fashion designated. Japanese use silk for making their national dresses Kimono.
2. Silk fiber is used for water absoption, dyeing, thermo tolerance, insulation and lusture. Raw silk is used for parachute, tire lining, electric insulator, artificial blood vessels and surgical sutures.
3. Silkworm pupae is used for oil extraction, protein extraction, amino acid and Vitamin B2 preparation. Diseased(muscardine) silkworm larvae and pupae are used for vitamin E preparation.
4. Sericulture provides employment to unemployed manpower in the country.
LIFE CYCLE OF SILKWORM
Mulberry silkworm is a completely domesticated insect which is never found wild. Some topographic species of this worm have been developed through differentiation, selection and feeding. On the basis of generation produced per year, three distinct groups viz univoltine (one generation per year), bivoltine (two generations per year) and multivoltine (many generations per year) are being recognized. The mulberry silkworm passes through complete metamorphosis, producing four distinct stages:-
1. Egg: Univoltine race deposits eggs in spring which undergo diapauses and hatch out only in next spring. Multivoltine race deposits eggs in non-hibernating eggs and produce 2-7 geberations in a year. The eggs are laid in clusters on the surface of the mulberry leaf or artificially prepared butter cups. A female lays eggs about 400-500 eggs popularly called as silk seeds. The eggs are small, oval in shape and creamy white in colour. At the time of hatching, they turn black and hatch in 9-11 days.
2. Larvae: Newly hatched larvae are tiny, 3 cm cylindrical in shape and black or dark in color. They become lighter and smoother during different succeeding instars. There are five larval instars - first three are known as young worms and rest two instars are called as grown up worms. The tiny caterpillar immediately after hatching begins to feed on mulberry leaves and grow rapidly. They molt d 5 times to reach maturity. After the last molt, larvae raise their head and search shelter for resting. They secrete silken thread and cover themselves. The larval stage lasts for 18 - 24 days.
3. Pupa: Full grown larvae begin to spin their cocoons. This takes about 3 days of constant motion of the head from side to side at the rate of 65 a minute. Larvae extrude a fine filament of pulpy material (brin or fibroin) through the silk glands. These are stuck together by sericin or silk gum in the spinneret to form a single continuous fiber of about 500 mm long and 0.02 mm diameter. The cocoon is oval in shape and white or yellow in color. After completing the process of silk secretion, the larva pupates inside the cocoon which provides protection for the developing pupa. The pupa is reddish brown in color. This stage lasts 11 - 14 days.
4. Adults: Adults come out by making a small hole through the cocoon. It is creamy white in color and measures 30 mm with a wing span of 40-50 mm. Female is bigger than male. They mate immediately after the emergence, do not take food and survive only for 2 - 3 days. The empty cocoons (after adult emergence) are called pierce cocoon. They are of low value because of staining and unreel ability into continuous threads.
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Entomology
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