Silkworms are holometabolous insects. What do they mainly eat, and why do they spin silk?

China is the country of origin for silkworm rearing and the main source of silk raw material, holding an important place in human economic life and cultural history. When I was in primary school, my favorite thing was raising a few silkworm babies at home. So what food do silkworms mainly eat? Why do they spin silk?

I. A brief introduction to silkworms

The silkworm is an insect of the order Lepidoptera and the family Bombycidae, and it is a holometabolous insect. The most common is the mulberry silkworm, also known as the domestic silkworm (Bombyx mori), which originated in China. Its developmental temperature range is 7 to 40°C, and the suitable rearing temperature is 20 to 25°C. It is mainly distributed in temperate, subtropical and tropical regions, and China had already begun rearing silkworms artificially at least 3000 years ago. The life of a silkworm goes through silkworm eggs—newly hatched silkworms—mature silkworms—cocoons—silkworm moths, a total of more than fifty days.

II. What food do silkworms mainly eat?

Silkworms can be divided into several kinds, such as mulberry silkworms, tussah silkworms, castor silkworms, Chinese oak silkworms and amber silkworms, and different kinds of silkworms eat different foods.

1. Mulberry silkworm

The mulberry silkworm is the domestic silkworm. Its silk is an excellent textile fiber and the raw material for satin, and its main food is mulberry leaves.

In addition to mulberry leaves, the domestic silkworm can eat many foods, such as cudrania leaves, elm leaves, fig leaves, artemisia willow leaves, dandelion leaves, lettuce leaves, romaine lettuce leaves, black salsify leaves, salsify leaves and so on. Although many leaves can be fed to silkworms, their leaves generally have low nutritional value and cannot rear silkworms well, so they have no practical significance. With modern scientific progress, silkworms can also eat silkworm feed, but its main ingredient is also mulberry leaf powder. However, mulberry leaves are the most suitable natural food.

2. Tussah silkworm

The tussah silkworm feeds on the leaves of plants of the genus Quercus in the family Fagaceae, such as sharp-toothed oak, Mongolian oak and Quercus dentata, and can also eat the leaves of plants such as artemisia willow, Malus baccata, chestnut, maple, pear and apple. Tussah silk is the raw material for tussah pongee, and tussah silkworm pupae are edible and, together with the moths, are raw materials for the chemical, pharmaceutical and food industries.

3. Chinese oak silkworm

The main food of the Chinese oak silkworm is the leaves of plants of the genus Quercus in the family Fagaceae, such as Liaodong oak, Mongolian oak, Quercus variabilis and sharp-toothed oak. The cocoon of the Chinese oak silkworm is green in color and can be reeled into silk. The silk is beautiful and soft, can maintain its natural green color without dyeing, and has a unique luster.

4. Castor silkworm

The main food of the castor silkworm is castor leaves, and it is mainly used as a raw material for spun silk, spinning castor spun silk.

5. Amber silkworm

The main food of the amber silkworm is the leaves of nanmu, and the cocoon of the amber silkworm is golden yellow in color and can be reeled into silk. Its woven fabric is used to make valuable clothing.

III. Why do silkworms spin silk?

Spinning silk and forming a cocoon is an instinct of the silkworm, and the silkworm's spinning of silk and formation of a cocoon is related to the silk gland organs in the silkworm's body.

1. From the perspective of the silkworm's growth process, because the silkworm eats a large amount of mulberry leaves during the larval stage, the various amino acids in the mulberry leaves are absorbed and stored by the silk glands in the silkworm's body. As the silkworm ages, the silk glands also enlarge. Before spinning silk and forming a cocoon, the silkworm's chest can be seen to be slightly transparent in appearance, precisely because a large amount of protein has accumulated in the silk glands.

2. From the physiological perspective of the silkworm, the reason the silkworm spins silk and forms a cocoon is that the protein composing the silk glands is made up of amino acids. If there are too many amino acids in the silkworm's body, the silkworm will be poisoned, so the silkworm needs to eliminate amino acids by spinning silk to achieve the purpose of detoxification.

3. In addition, as a holometabolous animal, the silkworm is very fragile at the key stages of metamorphosis. At this time, the behavior of spinning silk and forming a cocoon can both avoid natural enemies and protect itself, and allow it to safely turn into a pupa inside the cocoon, and let the organs in the pupa's body transform into the form of a silkworm moth, finally emerging as a silkworm moth.

The above is an introduction to what food silkworms eat. Generally we raise domestic silkworms, which mainly eat mulberry leaves, and other green vegetable leaves can also be eaten in appropriate amounts.