Silkworm Breeding, that nutritious caterpillar.

I will begin with the silk worm, as most of you will start with worms ordered from various suppliers.
When you receive the silk worms they are typically housed in a deli cup habitat or “pod”.  As silkworms have a low immune system you must be very careful with cleanliness and moisture. The pods are not ideal for growing the worms without bacteria or mold; therefore I usually move mine over to separate containers.  I use the sterilite 6Qt (5.7 L) Tupperware containers that state they are for shoe storage.  Any Tupperware that is around that size should do.  I then cut out the lid and hot glue some screen to it as shown below.  I also cut some gutter guard (Link to Lowes Gutter Guard) and place that inside for the frass to fall through. You can raise it up with bottle caps or some equivalent.

If the silk worms are kept too humid they may develop mold or bacteria and die, I find that the container noted above works well. I have not had a mass die off to date, that were not related to the silk worm virus.

Note about the silk worm virus: The silk worm virus is airborne and is the reason you will see many suppliers out of stock for long periods of time. If you get hit with the virus you have to clean everything with a bleach and water solution and air out the house. The virus causes the worms to turn in to a nasty dark liquid goo. I have been hit with it twice and was able to overcome it after thorough cleaning and not having silk worms in the house for 2-3 months. If you get the virus with a batch of silkworms and you keep ordering worms before you take necessary precautions to rid your home of the virus, then each shipment that comes in will become infected and die.

Feeding the silk worms can be tricky. If you start them off on mulberry leaves it can be difficult to get them to eat the chow or any alternative later. I tend to use the silkworm chow from mulberry farms or coastal silkworms and also gutload with greens and carrots. You can feed them non-mulberry food; however they will not survive well without some mulberry in their diet (at least 25% or more). If you run out of mulberry chow you can feed them greens and shaved carrots and they will survive temporarily. I have had some who were fed mulberry chow the first half of their life and then fed greens and carrots the second half. They survived until either fed off or cocooned. Those that cocooned did result in healthy moths.

Silkworms get their water from the food so it is not necessary to provide any type of water source.

I usually put enough food in the container to last up to 2 days. After about 2 days the remaining food may be dried and need replacing. I also use this opportunity to empty out any frass from the container. You can lift the gutter guard with worms on top and pour out the frass from the container. Be sure you have thoroughly washed your hands prior to touching the containers, worms, or food.

Here are some zebra silks just prior to cleaning the container.

Once the silk worms are full grown it is time to think about allowing them to cocoon. At this point I usually separate the ones I plan to keep for breeding and put them in a larger container that is set up for breeding.

For this stage I use a sterilite 56Qt (53L) plastic tub. I have cut holes in the side and top and hot glued screen as it is used for silkworm breeding and other purposes.  I place some gutter guard on one side and toilet paper rolls on the other. I put food on the gutter guard side so that the worms can continue to eat until they are ready to cocoon. Most migrate over to the rolls to cocoon, while others will cocoon just about anywhere.

Once the silk worm begins spinning you must leave it alone. The worm only has a limited amount of silk and if disturbed during the spinning process it may not recover.

You may also find the occasional yellow cocoon. Do not be alarmed as this is normal. I have read that all silk worm cocoons are yellow in the wild. It is due to selective breeding that they are now white.

It has been written that moving the cocoons is trouble; however I have moved them every time and not had any issues. I usually wait about a week after they spin cocoons to move them. I gather up all of the cocoons, very carefully, and place them in a new container that is lined with paper towels. I place the cocoons in a circle around the edge of the container and wait for moths to hatch.

Moths will hatch within about 2 weeks, give or take.  Just prior to coming out you can see one end of the cocoon becoming wet as the moth squirts cocoonase on the silk to dissolve the cocoon. Once the moth has emerged you will see a hole at the end of the cocoon.

Video of Moth Emerging

Now that you have silk worm moths you may wonder what to do next.

The moths cannot fly and do not eat. They have been bred for silk for thousands of years and the wings have become vestigial.  The males tend to be smaller than the females, but with larger wings and antennae. The females will be larger, filled with eggs, and have smaller wings. The females will scent (secrete a pheromone) which drives the males crazy. You will notice dark liquid on the paper which is part of their secretions when excited.

Males can mate multiple times, whereas females mate once. Once a male and female connect they may stay connected for up to 24 hours. You can safely separate them after several hours by gently turning them like removing a key from a lock. You must be careful not to damage the female’s ovipositor as this will affect her ability to lay eggs.  Once I separate them (or if you are afraid to separate them just do this to the mating couple) I put a toilet paper roll (you can also use a plastic cup) over her to control the area of egg laying. This will result in a nice circle of eggs that can be cut out later.

When the eggs are first laid they will be yellow. After several days they will change to tan and then eventually gray. If they do not change color, then they are infertile.

At this point you can leave them at room temp or higher to hatch, or opt to store them for later use. If you would like to store them for later use, you can cut out the egg circles and place them in zip lock bags. I then date the bags and place them in the crisper drawer of the refrigerator until I am ready to hatch them. They will save in the refrigerator for several months. I use an incubator to hatch my eggs that is set to 85 degrees.

Here is a female with some eggs that were not controlled with toilet paper rolls.

When I am ready to hatch the eggs I place them in to a petri dish.

I keep the petri dish on top of some moist paper towels that I mist daily. The eggs need some moisture, but not enough to cause mold or to come in direct contact with the eggs. I also keep them in my incubator at around 80-85 degrees. At lower temperatures it can take weeks or months for them to hatch. When I tried at room temp with a light bulb above them it took up to 2 months for them to hatch.

When the eggs hatch you will see tiny black worms, at this time you should put small amounts of food in the container with them. The best results seem to be with using a cheese grater and grating a small amount of food over them. You can remove any dried out food if the worms are not on it.

Don't mind the baby mantis trying to get a silk worm treat. 

As the worms grow they will migrate over to the food which is also a good way to get them where you want them. If you need them to move to another spot so that you can clean the other, just put the food where you want them and they will move. It will take a couple weeks for the worms to grow to a decent size, depending on food availability and room temperature.  If you would like to slow their growth down, you can deprive them of food. I have read that they can go up to a week without food, although I have not withdrawn food for more than 2 days at a time.

Here is a macro of baby worms.

From here you basically just feed them and clean then and once they grow in to their second instar I move them to the tupperware and start over from the beginning.

So there you have it….my silk worm rearing and breeding methods. I hope this is helpful to you.

Bonus Pics (my boys love to eat silk worm moths once they are done breeding)