The body of silkworm is divided into three parts: head, thorax and abdomen, consisting of thirteen segments.

The head has a mouth and six pairs of single eyes, and the chest has three pairs of feet (thoracic feet) with pointed tail ends. There are four pairs of round fleshy legs (ventral legs) and a pair of tail legs on the abdomen. The abdominal legs help silkworms crawl around on mulberry leaves.

Silkworms are metamorphosed insects, the most common of which are mulberry silkworms, also known as domestic silkworms. They are one of the economic insects that feed on mulberry leaves and spin silk and form cocoons. Silkworms originated in China. Their development temperature is 7-40℃, and the suitable breeding temperature is 20-30℃. Silkworms live on mulberry leaves. After eating mulberry leaves continuously, their bodies will turn white. After a period of time, they will begin to peel. During the peeling process, they will last for about a day, as if they are sleeping without eating or moving. This is called "dormancy".

After one molt, it becomes the second-instar larvae. It sheds its skin once and is one year older. The larvae will molt four times to become the fifth-instar larvae, and then eat mulberry leaves for 8 days to become mature silkworms. Start spinning silk and cocoon.

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Extended information:

Insects are a family in the animal kingdom Huge and diverse, with many types of perversions , there are mainly the following 5 types of metamorphosis:

1. Segmentation metamorphosis

For example, the Protocera insects of the subclass Apteryx have the same body size and organs during their larval stage and adult stage. In addition to the difference in development level, the number of body segments in the abdomen gradually increases from 9 to 12 segments.

2. Epimetamorphosis

For example, the Collembola insects of the subclass Apteryx have basically the same shape as adults when they are larvae. However, during the growth and development process, the sexual organs gradually mature, and the antennae, The number of caudal segments continues to increase, and the individual size changes somewhat.

3. Proto-metamorphosis

This type of metamorphosis is only seen in the Ephemeroptera insects of the subclass Pterozoa. It goes through the sub-adult stage from larvae to adults. This period is short and appears. Resting state.

4. Incomplete metamorphosis

The main characteristic of this metamorphosis is that the adult insect gradually undergoes three stages of growth and development: egg stage, larval stage and adult stage. manifest.

5. Complete metamorphosis

Insects that conform to this form of metamorphosis are characterized by going through four stages of egg, larvae, pupa and adult in their lifetime. Larvae and adults are very different in external morphology and life habits. When the larvae mature and molt and turn into pupae, the larval form disappears, and the pupal stage form is basically similar to that of the adult worm. For example, Lepidoptera moths and butterflies have no antennae and wings when they are larvae, and have chewing mouthparts. After turning into adults, all the larval forms disappear. Not only do they have wings to fly freely, but their mouthparts also change to siphoning mouthparts. Also belonging to the holometabolous form of Lepidoptera are Coleoptera, Diptera, Hymenoptera, Neuroptera, etc.

In some holometabolous insects, the larvae of each instar are also different in shape. This metamorphosis is called compound metamorphosis, such as carabid and colicine of Coleoptera, parasitic flies of Diptera and Hymenoptera. Ji Feng et al. In short, the higher orders in the subclass Pterozoa are all complete metamorphosis forms.

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