1, 1st instar silkworm: brown in color, very small, reddish-black in head, about 2mm in length and 0.5mm in width. After eating, the body color gradually becomes lighter, and at the end of the instar, the body length reaches 4-5mm. 2. Second instar silkworm: The head is reddish black, the back and chest are white, and the back and abdomen are gray. At the end of the second instar, the body length is about 1cm. 3. 3rd instar silkworm: The head is no longer black, but gray. At the end of 3rd instar, the body length is about 1.5-2cm.

Morphological characteristics of first and third instar silkworms

1, First instar silkworm: brown in color, very small in body, with fine hairs on the body surface, reddish-black in head, like ants without long legs, with a body length of about 2mm and a body width of about 0.5 mm. After eating, the body surface color gradually becomes lighter, and at the end of the age, the body length can reach about 4-5 mm.

2. Second instar silkworm: The head is still reddish-black, the back and chest are white, and the back and abdomen are gray. At the end of the second instar, the body length is about 1cm.

3. 3rd instar silkworm: The head is no longer black, but gray. At the end of 3rd instar, the body length is about 1.5-2cm.

4. Four-year-old silkworm: The body of the four-year-old silkworm is long, the head is grayish white, the body gradually becomes bigger and fatter, and the markings are very obvious. At the end of the age, the body length is about 2-3cm.

5. Fifth instar silkworm: The head of the fifth instar silkworm is grayish white, the abdomen is large, the tail foot is obviously open, and the body gradually becomes obese. In the middle and late stage, the body length can reach more than 5cm, and the weight can reach about 1 10,000 times the weight of the ant silkworm. At the end of the period, it gradually showed the characteristics of ripeness, specifically, the silkworm dung changed from hard to soft, from dark green to leafy green, the desire to eat decreased, the front digestive tube was empty, and the chest was transparent. Then the silkworm stopped eating completely, its body shortened, its abdomen gradually became transparent, its head and chest were raised, its mouth spit silk, and it swung up and down.

The second and third instars become fourth instars in a few days.

1, the incubation time of resting eggs is about1-14 days, and that of non-resting eggs is about 9- 12 days.

2. It takes about 3-4 days for a first-year silkworm to become a second-year silkworm, 2-3 days for a second-year silkworm to become a third-year silkworm, 3-4 days for a third-year silkworm to become a fourth-year silkworm, 5-6 days for a fourth-year silkworm to become a fifth-year silkworm, 6-8 days for a fifth-year silkworm to become a mature silkworm, and 4-5 days for a mature silkworm to pupate.

3. It takes about 10- 15 days for silkworm chrysalis to emerge.