explain life history of skil morh
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The most popular among the silk moths is Bombyx mori which is popularly called the mulberry silkworm, as its main feed is mulberry plant. The life history of mulberry silk worm consists of four stages- the adult, the egg, the larva (catripillar) and the pupa stage.
Adult stage:
The adult silk moth is about 2.5 cms in length and pale creamy or white in colour. The moths are dioecious (male and female moths are separate). In the female, due to the heavy body and generally weak wings flight is impossible. The female moths are larger than the male.
The body of the moth is divided into three parts namely head, thorax and abdomen. The head has got a pair of compound eyes and there are two antennae. There are three segments in the thorax- these are the prothorax, the mesothorax and the metathorax. The prothorax is quite big. The moth has got three pairs of legs and there are two pairs of wings. The female moth generally does not feed during its very short life of about 2-3 days.
Fertilization:
After copulation, fertilization takes place. Just after the emergence from the pupa, the male moth copulates with the female for about 2- 3 hours and then they separate. After fertilization the female starts laying eggs and it takes about 24 hours to complete the process.
On an average a single moth can lay about 400-500 eggs. The quantity of eggs depends on the climatic conditions and the supply of food material to the caterpillar from which the female moth is developed. They (eggs) are usually laid on the upper surface of the mulberry leaves. The eggs are usually in clusters and are enclosed in a gelatinous substance which is secreted by the female moth. The gelatinous substance helps in the attachment of the eggs to the leaves.
The eggs are minute in size, spherical in shape and white in colour. The weight of about lOOOeggs will be less than one gram. Gradually the eggs become dark in colour. It has been observed that in mulberry silk worms there are two types of eggs.
These are the diapauses type and the nondiapause type. The silk worms of temperate regions lay the diapause type whereas the silk worms of subtropical regions (as in India) lay the nondiapause type of eggs. In diapause type of eggs there is a hibernating stage (resting stage). The nodiapause type of eggs are nonhibernating and consequently the moth will take a very short time to complete the life cycle. In fact, the mulberry silk moth in India can complete five life cycles per year.
Hatching of eggs:
After 10 days of incubation, the eggs are hatched into larvae called the caterpillar. The hatching stage is the most critical stage in the life history of the silk moth. The caterpillars are voracious eaters and need a continuous supply of food (mulberry leaves). If there is insufficient supply of food the caterpillars will not grow properly. Sometimes due to lack of food the larva may even die.
Caterpillar (larva):
The newly hatched larva is about l/8th of an inch in length. The body is yellowish white in colour. The larvae are provided with well developed mouth parts which are adopted to feed on the leaves of mulberry. In structure, the larval body is made up of 12 segments and the abdomen is made up of 10 segments and has 5 pairs of pseudo-legs. In addition to this, in the last anal segment there is a small dorsal horn. The silk worms undergo moulting (ecdysis) four times and
Adult stage:
The adult silk moth is about 2.5 cms in length and pale creamy or white in colour. The moths are dioecious (male and female moths are separate). In the female, due to the heavy body and generally weak wings flight is impossible. The female moths are larger than the male.
The body of the moth is divided into three parts namely head, thorax and abdomen. The head has got a pair of compound eyes and there are two antennae. There are three segments in the thorax- these are the prothorax, the mesothorax and the metathorax. The prothorax is quite big. The moth has got three pairs of legs and there are two pairs of wings. The female moth generally does not feed during its very short life of about 2-3 days.
Fertilization:
After copulation, fertilization takes place. Just after the emergence from the pupa, the male moth copulates with the female for about 2- 3 hours and then they separate. After fertilization the female starts laying eggs and it takes about 24 hours to complete the process.
On an average a single moth can lay about 400-500 eggs. The quantity of eggs depends on the climatic conditions and the supply of food material to the caterpillar from which the female moth is developed. They (eggs) are usually laid on the upper surface of the mulberry leaves. The eggs are usually in clusters and are enclosed in a gelatinous substance which is secreted by the female moth. The gelatinous substance helps in the attachment of the eggs to the leaves.
The eggs are minute in size, spherical in shape and white in colour. The weight of about lOOOeggs will be less than one gram. Gradually the eggs become dark in colour. It has been observed that in mulberry silk worms there are two types of eggs.
These are the diapauses type and the nondiapause type. The silk worms of temperate regions lay the diapause type whereas the silk worms of subtropical regions (as in India) lay the nondiapause type of eggs. In diapause type of eggs there is a hibernating stage (resting stage). The nodiapause type of eggs are nonhibernating and consequently the moth will take a very short time to complete the life cycle. In fact, the mulberry silk moth in India can complete five life cycles per year.
Hatching of eggs:
After 10 days of incubation, the eggs are hatched into larvae called the caterpillar. The hatching stage is the most critical stage in the life history of the silk moth. The caterpillars are voracious eaters and need a continuous supply of food (mulberry leaves). If there is insufficient supply of food the caterpillars will not grow properly. Sometimes due to lack of food the larva may even die.
Caterpillar (larva):
The newly hatched larva is about l/8th of an inch in length. The body is yellowish white in colour. The larvae are provided with well developed mouth parts which are adopted to feed on the leaves of mulberry. In structure, the larval body is made up of 12 segments and the abdomen is made up of 10 segments and has 5 pairs of pseudo-legs. In addition to this, in the last anal segment there is a small dorsal horn. The silk worms undergo moulting (ecdysis) four times and
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