Keeping - Breeding Silkworms
How To Keep And Breed Silkworms (Bombyx mori)
Silkworms have been used for thousands of years as a means of harvesting the silk they create around their cocoons. A single cocoon can yield as much as a 3,000 foot strand of silk. This sounds like a massive amount but it takes 2,000 to 3,000 cocoons to make a single pound of silk. In addition to creating silk, the larval stage of these moths make wonderful feeder insects for reptiles and other insectivores.
Ventilation is key when housing Silkworms. Silkworms prefer dry environments and become susceptible to illness when moisture is allowed to accumulate. Screen mesh adhered to the top of their housing containers is an ideal way to allow evaporating moisture to escape. You can learn about this technique on our Custom Enclosure Covers page or you can simply cut an opening and glue the screen in place.
Silkworms don't require large amounts of space to thrive. Just about any Rubbermaid container will suffice. Use your judgment based on your needs. You don't want your worms competing for space. If you find that the amount of worms you have versus the space they have doesn't appear to work, split your group into 2 containers or upgrade to a larger container.
Ventilation is still important when housing your moths. The moths themselves do not fly and don't require a vast amount of space to breed. In order to control, contain and locate the eggs that the female lays, you will want a fair amount of floor space to accommodate a suggested method for containing the eggs. Once you see your female and male copulating, which will be noticeable because their abdomens will be attached at the tip, you will want to prepare to contain the female, once they have separated. The simplest method for doing this is to place a piece of fresh paper towel in the tank that has been cut roughly 1" larger than a small plastic container that you will use to cover the female. By placing a small container over the female and having it rest upon a cut piece of paper towel, you will be able to control where she lays her eggs and will be able to extract the eggs for incubation with ease.
If you use this method, your moth enclosure should have enough floor space and height to accommodate the small containers for the amount of moths you will be doing this with. Deli cups and small plastic cups are ideal for this technique. The eggs can then be easily transferred into petri dishes for incubation.
Your cocoon housing should have enough height to adequately place toilet paper rolls upright within it. Another option is to place wide opening mesh in the cocooning enclosure. This is where the silkworms will likely cocoon, though some may choose to just adhere themselves to the side of the container. You will need as many rolls as you do worms that you wish to allow to complete metamorphosis. This will vary, depending upon each person and their requirements for sustaining their colony. The worms that are transferred into the cocooning container should continue to be fed until they begin to cocoon. Once they emerge from their cocoons, which takes anywhere from 10-14 days depending upon temperatures, you can remove the moths and place them within the paper towel lined container for breeding.
Many people have great success without using any type of substrate material. Not using a substrate just means you need to be vigilant in keeping your colony clean. Moisture + frass (their waste) + old food = mold, bacteria and disease. Some people have found that using varying size mesh and screen works wonderful for keeping the tubs clean. They line the bottom of the tubs with the mesh and most of the frass will fall through, away from their worms. Vinyl gutter guard rolls are also great for this purpose. Plastic or vinyl is great because after you move your worms into clean containers, the vinyl or plastic can be cleaned and recycled for use again.
You want to limit your handling of these worms because you can be the cause of a bacterial and disease issues. Always wash your hands and thoroughly dry them before you handle your worms. It is extremely important that you understand the seriousness of this section. Many people lose their worms because they failed to wash their hands and introduced bacteria or disease into their colony. Wash your hands whenever you will be placing them within the enclosure, this includes during feedings. Again, WASH YOU HANDS!
Temperatures play a critical role in the success and failure of your project. Newly hatched silkworms are the most susceptible to temperature issues and should be housed between 78° - 85°F until they have reached at least 3/4-1" in length. At this point they can be kept at slightly cooler temperatures as they have matured past the critical stage of their development. In an ideal world they should be reared in an incubator during this period. This will allow you to control their temperatures without them fluctuating.
For optimal growth, your colony should also be housed between 78° - 85°F. If you wish to prolong their growth rate, they can tolerate temperatures as low as 68°, though maintaining the cooler temperatures around 70°-72°F would be safer. (Some people have maintained their worms at cooler temperatures but my research has shown that disease is more probable when the worms are kept in those cooler temps as it impairs their immune system versus keeping them at their optimal temps.)
Unless you have access to mulberry trees, which the leaves of these trees are their primary food source, you will be feeding silkworm chow. Silkworm chow is readily available online at different merchant stores. The chow you purchase will come with instructions. make sure you follow those instructions. Many people find that using a cheese grater is ideal for feeding their worms in all stages. You will want to grate the food directly on top of your worms. The worms are not very active in their movement and this has proven to be the best method for ensuring everyone is eating. Only feed them what they can eat. You want to avoid having wasted food in the enclosures because this can lead to mold, which can lead to bacteria and disease. The worms have voracious appetites so you will likely have to feed them several times per day as they will quickly decimate whatever fresh food is available.
You do not need to provide water for silkworms. They will get all of the water they need from the food they eat.
Bombyx mori goes through 4 stages of life; egg, larvae (silkworm), pupa and silkmoth (Bombyx mori). Eggs take around 7-14 days to hatch. At this point they emerge as the larvae we choose to feed our reptiles, the silkworm. The worm will go through 5 instars (an instar is the time between molts) over the course of 25-30 days and will then create a cocoon to protect itself during the next stage of its life as a pupa or chrysalis. The pupa will remain in the cocoon for around 10-14 days. (All of the time frames are dependant on your temperatures and feeding schedule.) The moths that emerge from the cocoons will have one purpose, which is to breed. They do not eat or drink as adult moths. They will survive for around 7 days or so before they expire and the next generation of life begins.
Once your moths emerge from their cocoons, the female will begin scenting the paper towel. This will be noticeable by the discoloration left on the paper towel. The pheromones she leaves behind will drive the male moths crazy. They will frantically seek out a female and may be observed flapping their wings in bursts. Once they locate a female they will copulate. The 2 will be attached by the ends of their abdomens for anywhere between 12-24 hours. Once they have separated, this is when you will want to place a container over the female as instructed in the enclosure section, to control her egg-laying. She will lay eggs over the course of 3 days. You can then take the paper towel and transfer the eggs into the awaiting petri dishes.
Eggs are best incubated within petri dishes, inside an incubator, set at 83-85°. At these temperatures the egg will begin hatching in 7-10 days. They can be fed and kept in the incubator until they have reached 3/4 - 1" in length. At this point in time they should be removed and placed inside a heated container outside of the incubator. A small paintbrush can be used to move the worms from the petri dish. They are very delicate and care must be taken when moving them around. Remember to wash your hands before handling the worms or their food. You are the biggest threat to your colony.
Author: Richard Brooks