Last year we had 8 silkworms. They got big and fat, spun cocoons, emerged as moths, and laid eggs. I put the eggs in a fridge in a ziploc bag, and then a couple of months ago I noticed that the leaves were coming back on the mulberry trees so I took them out of the fridge and put them in a cardboard box. A few weeks later they hatched.
I didn't count how many eggs we had, they were just laid over a single section of an egg carton and it didn't seem all that many. But we ended up with HUNDREDS of baby silkworms.They started out tiny, like little black pencil marks, but they slowly got bigger.
As soon as they were big enough to handle I started trying to give them away. I started off giving people about 10 in a box, like we had been given last year, but as they got bigger and were eating more leaves I was keen to get rid of them and was offloading 20 or 30 at a time.
I don't know how many we had to start with, because they were too small and wriggly to count, but after I had given silkworms to everyone who I could convince to take them we still had over 100. They outgrew the shoebox, and I ended up dividing them over 3 shoeboxes and a massive archive box. They were getting through a grocery bag of leaves a day - luckily there are some very big mulberry trees in the parks near us. I started to feel like the local Crazy Silkworm Lady, and got to know lots of neighbourhood dog walkers and joggers on my leaf-picking missions.
This website, which has some very good silkworm information, says the caterpillar stage takes about 1 month, but our silkworms hatched seven weeks ago and only began spinning cocoons last week. I wonder if it is because I had so many of them, that they took longer to eat enough mulberry leaves to reach the right size, or if it's just a more slowly maturing variety. [Or perhaps the website is being optimistic, in the same way that recipes deliberately underestimate how long it takes to cook onions, because they know no-one wants to look after caterpillars for two months?]
At the moment about a third of them have spun cocoons, and most of the rest are starting to look for corners and places to spin in. A few are still eating leaves, and I am concerned that if they don't start spinning soon they will grow to the size of spaniels and start frollicking up and down the hallway. I am also slightly scared to think of how many eggs we will end up with if all the moths hatch at the same time.
But it has been a great "Very Hungry Caterpillar" style life cycle demonstration for the children, and also good to be able to show them where silk comes from. It does make me wonder how anyone manages to produce silk on a commercial scale. Do they have forests and forests of mulberry trees to feed the caterpillars? Or have they engineered a super strain of silkworms who really do spin cocoons after only a few weeks? And has anyone actually tried making silk from their cocoons at home?