My Silkworm Raising Diary
October 5, 2020 Cloudy
Having nothing to do in Sydney, a friend happened to be raising silkworms. I got a few newly hatched silkworms from him and, together with my grandson, began an experience of raising silkworms. Not far from my home, there is a mulberry tree with lush foliage. I picked some very tender mulberry leaves, placed them in a box, and the young silkworms started nibbling on the mulberry leaves.
October 8, 2020
The young silkworms ate mulberry leaves non-stop every day, gradually growing in size. After a few days, they slowly turned pale greenish-white, and a few days later, they began to molt. Before molting, the silkworm's head was black. The molting process took about a day. During molting, they neither ate nor moved. After the first molt, they became second-instar larvae.
I fed the silkworms four times a day: once in the morning, once at noon, once in the afternoon, and once before going to bed at night. In the dead of night, when I came to the cardboard box, I could clearly hear the rustling sound of the silkworms eating mulberry leaves. When they finished eating the leaves, they would lie still and not climb up the sides of the box.
The silkworm's body consists of three parts: head, thorax, and abdomen. The small head is flat and round, with compound eyes on both sides and a chewing mouthpart below. The thorax is made up of three segments, with three pairs of thoracic legs that help the mouthpart hold the mulberry leaves. The abdomen has ten segments, with four pairs of abdominal legs and one pair of anal legs that assist in movement. There are tiny hooks on the abdominal legs. When cleaning up leftover mulberry leaves, these small hooks firmly grip the veins of the remaining leaves, making them hard to remove. On both sides of the silkworm's body, there are nine pairs of small black spots, which are the spiracles for breathing.
October 12, 2020
The silkworms consumed a large amount of mulberry leaves and grew quickly. Their body color gradually lightened, becoming plump and white, truly endearing. A few days later, their appetite began to decrease until they stopped eating and moving, as if dead. In fact, the silkworms were in a dormant state. After a day or two, they would start molting. After molting, they resumed normal life. Young silkworms undergo a total of four molts. After the last molt, they enter the fifth instar. At this stage, the silkworms grow extremely fast, reaching a body length of seven to eight centimeters, and turn greenish-white. Their excrement changes from hard to soft and from dark green to leaf green. Their appetite decreases, and the amount of mulberry leaves consumed declines. Eventually, they completely stop eating. The thorax and abdomen become translucent. The silkworm raises its head and thorax, spits out silk threads, and sways left and right, up and down, searching for a place to spin a cocoon.
October 24, 2020
At this point, the silkworm attaches the silk it spits to the corner formed by two vertical surfaces of the cardboard box, creating a cocoon net that can hold the cocoon. It continues to spin silk, thickening the inner layer of the cocoon net, and the outline of the cocoon, i.e., the cocoon shell, begins to appear. After the cocoon shell forms, the cocoon cavity gradually shrinks. The silkworm's body bends backward at both ends into a C-shape. Its head keeps swinging, wrapping itself round and round with silk into a transparent ball. At this time, one can still see the silkworm's head swaying back and forth, tirelessly weaving the cocoon. Due to the massive amount of silk spun, the body greatly shortens. The swinging speed of the head and thorax gradually slows down. The cocoon gradually thickens, becomes opaque, and starts to harden. Inside, it slowly pupates. Two days later, the cocoon is formed.
October 28, 2020
Four days after forming the cocoon, I cut open the cocoon with scissors and saw the silkworm curled up quietly inside the cocoon shell. Its body color was pinkish-yellow. It already had the form of a pupa, but the body was soft.
November 3, 2020
Ten days after forming the cocoon, I cut open the cocoon again and saw the pupa lying quietly inside. There was a small heap of shed skin, now coffee-colored. The pupal skin had hardened. The head was very small, with compound eyes and antennae. The thorax had thoracic legs and wings. The swollen abdomen had nine segments.
November 8, 2020 Sunny
Waiting eagerly for the silkworm moth to break out of the cocoon. Twenty-four days passed. At 6:30 in the morning, when I came to the cardboard box containing the cocoons, I found one end of a cocoon soaked with a reddish-brown liquid, and then a small round hole appeared. About an hour later, a silkworm moth slowly crawled out of the small hole. The silkworm moth had emerged.
Its body was milky white with brown stripes, a pair of feather-like antennae, a large abdomen, covered all over with white scales, and two pairs of wings curled up. It crawled onto the cocoon and remained motionless. After a while, the two pairs of wings slowly spread out. The silkworm moth's wings were not capable of flying.
The silkworm moth's head was small and ball-shaped, with bulging compound eyes and antennae. The thorax had three pairs of thoracic legs and two pairs of wings. The abdomen no longer had abdominal legs. Only one silkworm moth emerged today, making it seem a bit lonely.
Inside the cocoon shell from which the moth emerged, the shed skin of the mature silkworm pupation and the pupal shell remained.
November 9, 2020 Sunny
At 6:30 in the morning, another four silkworm moths emerged from their cocoons: two male moths and two female moths. The male moths were smaller and moved quickly, while the female moths were larger and hardly moved. Three hours later, the male moths flapped their wings rapidly, searching for female moths. After finding a female, they began to mate, lasting for over eight or nine hours. During mating, the male moth occasionally flapped its wings. After mating, the female moth lay still in place. Three hours later, it laid eggs. At that point, the male moth mated again with the female moth that had emerged the previous day.
November 11, 2020 Sunny
A few days passed, and one by one, the silkworm moths emerged from their cocoons. The two pupae from the previously cut-open cocoon shells also transformed into moths. According to the time calculation, the last cocoon should have taken another two days to break out, but it emerged at 8:00 in the morning. The head of the silkworm moth came out of the cocoon, but it remained in that state until 8:00 in the evening. I had to help it by cutting open the cocoon, only to find that the pupal shell on the moth's abdomen had not shed yet, and the wings had not fully developed. It was a premature moth.
November 13, 2020
Two days later, this premature moth died without shedding the pupal shell on its abdomen. After all the female moths laid their eggs, they stayed by the eggs, while the male moths flapped their wings, searching for the next female. They all stopped eating and gradually died after about ten days. I never got to see the young silkworms emerge from the eggshells, nor did I get to enjoy the joy of seeing them grow. Some moths died lying alone, while others died in a mating position.
Before the female moth laid eggs, I prepared a piece of white paper for it and spread it on the bottom of the cardboard box. However, the female moth did not lay eggs on the white paper. Instead, it crawled onto the box wall, laying eggs as it moved. The eggs were evenly attached to the box wall, about 400 in number, with no overlapping. The pale yellow eggs were even smaller than white sesame seeds. After laying eggs, the female moth lay still quietly. I covered the cardboard box with its lid to shield the eggs from light, allowing them to develop slowly inside.
November 15, 2020 Showers
Two days later, the eggs turned cream-colored.
On the third day, the eggs turned coffee-colored.
On the fourth day, the eggs turned dark brown.
November 29, 2020
In the following days, the color of the eggs stopped changing. During their development, they continuously absorbed nutrients. After fourteen days of waiting, the young silkworms emerged from the eggshells. They were black and tiny, just like ants, covered with fine hairs. Two hours later, they could start eating mulberry leaves. Silkworms are holometabolous insects, going through four stages in their life: egg, larva, pupa, and moth. Each stage has a different form. From laying eggs to becoming a moth, it takes a total of about fifty days. During this process, they convert mulberry leaves into silk, providing an important raw material for human silk spinning and weaving.
