Adult moth is about 2-5 cm in length and is pale creamy white in color. The body is divided into three parts namely head, thorax and abdomen. The head bears a pair of compound eye, a pair of antennae and the mouthparts. The entire body is covered with minute scales. Due to its heavy body, flight is not possible by female moth. The moth is unisexual and does not feed during its very short life period of 2-3 days.
Fertilization:
Fertilization is internal preceded by copulation just after emergence, male moth copulates with female for about 2-3 hours and if not separated them may die after few hours.
Egg:
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After copulation female starts egg laying which is completed in 1 to 24 hours. One moth lays about 400-500 eggs depending upon the climatic conditions and the supply of food materials to the caterpillar from which the female moth is obtained. The egg laying is always in form of clusters and covered with gelatinous secretion of the female moth, which helps them in proper attachment.
The eggs are rounded, white in color. The egg is about the size of a pin’s head. The weight of 2000 eggs comes about 1 gm the eggs after ten days of incubation hatch to a larva, called caterpillar. It is easy to tell when the young silk worm is mature inside the egg and ready to be hatched, because of the egg itself changes from a whitish to brown color. The caterpillars are voracious eaters and need a continuous supply of food. If the supply of food materials is less, the young caterpillar will die.
Caterpillar:
The silk worm, which hatched, is called caterpillar or larvae. The newly hatched caterpillar is about 1/3 inch of length. They are provided with well-developed mandible type of mouthparts. The caterpillar is twelve segmented and the abdominal region has ten segments with 5 pairs of pseudo-legs. A dorsal horn is present in anal segment.
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After four days, the molting takes place. Before this, the caterpillar stops eating and appears lifeless. It undergoes 40 molting after which the caterpillar got changed into 2nd, 3rd, 4th, and 5th in start. The full-grown caterpillar is 7.5 cm in length. It develops salivary glands, stops feeding and undergoes pupation. The time taken for full development of caterpillar from young to the well-grown stage varies with regard to temperature, humidity, food supply etc.