Whenever I run into former students, one of the things they always mention are the silkworms. I loved raising silkworms in the classroom because there are so many topics that can be covered that are in the school standards such as animal characteristics (habitat, diet, taxonomy, life cycle, etc.), ecology (they only eat mulberry leaves, what would happen if there were no more mulberry trees?), and economics (the silk trade). Fortunately, due to domestication, raising silkworms is easy and fun.
If you want to do it on hard level, you can buy the eggs. They are extremely small and you can find a lot of places online that will ship to you. I would not recommend this because they are very small and you have to feed them very young leaves, make a mush of the leaves in a blender, or just buy the silkworm mush the company sells. Their jaws are not strong enough to eat the regular leaves. Each egg is about the size of a period and when hatched, the silkworms are the size of a comma so you have to move them with a small paintbrush. My success rate with raising them from eggs is 25% so if you do this in the classroom, don’t raise them from eggs. Go get the ones that are regular sized.
Before you even buy anything, make sure you have a mulberry tree nearby. When I taught, I had to go to the district science center to get the silkworms and had to come by twice a week to pick their mulberry trees. Then one day, I was talking to someone about the silkworms and that person said, “Are you using the tree Mrs. Ancona (a former teacher) planted?” So it turns out right outside my classroom was a mulberry tree. The idea to raise silkworms with my kids came about when I noticed that I had two mulberry trees in my back yard. I got really excited and ordered the silkworms right away. I received them in a cardboard box full of mulberry leaves. They were about half as small as the picture above. I kept them in a lid of a cardboard box. You don’t need a cover. As long as you have food in the box, the silkworms will stay put.
Silkworms molt four times and have five instars (the time between molting). Each instar is about 3-4 days, even longer if you don’t feed them a lot. The first couple of instars, I would gather leaves and feed them once a day. Once they get bigger, I was picking leaves and feeding them twice a day or more. When I fed them new leaves, I would put the leaves on the table and pick each little guy/gal and place them on the leaves while I shook their poop out of the box. Then I would gather the leaves and place them back in the box. There used to be wild silkworms but that’s pretty rare. Domesticated silkworms are blind and somewhat dumb. All they do the whole day is eat and when they are full, they stick their heads in the air getting ready to molt.
The experience of raising silkworms has many benefits for kids. The silkworms are extremely soft and can’t bite. They move slowly and are soothing. There are some kids that have an unlimited amount of energy and just handling the silkworms calm them down. Also, if the class gets too crowded, you can tell them to be quiet so they can hear the silkworms chomping away on their leaves and it sounds just like rain.
After about a month, they get really fat and spend a lot of time sticking their heads in the air. That’s when you get some cardboard egg cartons and put it in the box. They spin their cocoons on the underside of the egg cartons or sometimes in the corner of the cardboard box. The weaving is pretty interesting. They make a secretion from below their mouth and this liquid silk hardens in the air. The silkworm makes a figure 8 with its head and makes a cocoon around itself. It is one continuous thread. I once took a cocoon and dipped it in hot water and rubbed it between my fingers and pulled the thread apart and it was a long string. I was not able to unwind the whole thread but that’s how silk is harvested. They boil the cocoons and women are trained to unwind the cocoons so that the thread is continuous and unbroken. Inside the cocoon the pupa is developing into a moth and the only way it gets out is to spit a chemical that burns a hole in the cocoon so that’s why they boil them inside the cocoon, to not ruin the threads. This part of the story of silk is sad for the kids and we let all the silkworms we raise turn into moths so raising silkworms in the classroom is not a money making endeavor.
It’s pretty exciting when they emerge. Their wings are wet and wimpy and their bodies are very fat. They flap their wings to dry them off. But don’t worry, these are domesticated silkworms so they can’t fly. Once they emerge, they only have one goal in mind, to mate. They don’t eat in this stage. The females are larger than the males and in the above picture, you can see something stick out of her behind that has pheromones that drives the males crazy. They eventually mate and the female lies hundreds of eggs on the leaves and cardboard box and then they both die. You can try to raise the eggs again or refrigerate the eggs for next year.