Silkworm Care Part 2 - Raising & Breeding Silkworms

Silkworm Care Part II - Raising & Breeding Silkworms By Rob Talkington (Wideglide)

Breeding Silkworms

With a little patience and practice breeding silkworms is fairly easy and the return is large enough that if you are successful with just a few mating pairs of silkworm moths you'll produce enough where you no longer need to purchase either eggs or silkies from a retailer.

The basic lifecycle of the silkworm is as follows. Keep in mind this is not a technical description detailing specific stages of growth for the silkworm itself, it is just a description of how it begins and ends for a silkworm.

• Eggs - First you've got a silkworm egg, which will hatch after about 3 weeks of incubation. The egg will start off as dark gray to black in color and just before the silkie hatches that egg will turn to a light gray and sometimes become transparent.
• Hatchling Silkie - When the newborn silkie hatches it is no more than about an eighth inch in length. This is a very delicate time for a silkworm so keep this in mind.
• Adult Silkworm - Depending on temps and food, in about 3 weeks, the silkworm can grow to as much as about 4" in length and be as thick as your ring finger!
• Spinning Stage - The silkworm will eventually stop eating, have one last defecation and then actually shrink some. When this happens it is ready to spin its cocoon. This spinning last about 3-5 days as long as the silkworm's cocoon is not disturbed while it is spinning. If it is disturbed the silkworm must start all over again in a new location.
• Cocoon - Again the time frame here depends on temperatures as well as other factors like how healthy the silkworm was when it created its cocoon. Anywhere from 3 to 6 weeks later and the silkworm will have mutated into a moth and the moth will break out of the cocoon.
• Moth - Once a moth hatches it looks for a mate of the opposite sex. The moths do not eat, drink or fly due to generations of domestication by humans. They mate, lay eggs then die in about 5 or 6 days.
• Eggs - Once again back to eggs. Once the moth lays the eggs they will be yellow in color. If they are fertile they will turn to a dark gray or black color. This is when you put them in the fridge. If they are not fertile they will remain yellow.

Eggs - Incubation and Hatching

When you are ready to incubate and hatch a colony of silkworm eggs you have a number of options. I use an incubator but have read of many people just having the eggs sit at room temperature and be successful. I do not know if their environment more closely matched that of what has been considered optimal conditions or not so I'll explain my method and you can choose to do what you think works best for your situation.

I usually place my eggs into a 5"(approx.) Petri dish. If they are loose I will take some Elmer's non-toxic stick glue and spread a thin layer on the Petri dish and sprinkle the eggs on the glue. Most of the time my eggs are stuck to small card of paper because of how I breed my silkies so rarely do I use the glue. If the eggs are on the card I just put the card with the eggs stuck to it in the Petri dish. I do not glue the card to the dish but that's just me, if you want to, go ahead and glue the card down.

I have the incubator set to 84 degrees and have a reservoir of water in the bottom to keep the humidity at about 75%. If you don't have an incubator one method I've read about indicates to put the Petri dish on something such as a kitchen counter and place a bowl over the Petri dish. Within the bowl place a moistened paper towel to provide the necessary humidity. Also place something under one edge of the bowl to allow for ventilation. You can apply heat in the form of a lamp if desired but keep an eye on the Petri dish to make sure it does not build up condensation inside. Condensation will drown the eggs and you won't be very successful.

The length of time for incubation will depend on the temperature as well as other factors. Usually my eggs will begin to hatch in about 3 weeks and will continue to hatch for about 3-5 days. Once the eggs begin to hatch you will need to provide food for the hatchlings.

Hatchling Care

So your eggs have begun to hatch and now you need to get them some food within 36 hours or they will begin to starve. Since there are still eggs that have not hatched it is important that you do not smother these unhatched eggs with the food. One method is to take a couple of tooth picks and place them close to the eggs. Cut a couple of tiny strips of chow and place the chow right on top of those toothpicks. The hatchling silkies will climb to the food as long as it is fairly close to them. It is important for the food to be near the hatchlings because at this stage they will not travel very far looking for food. They will just starve and die. Another method you can use is to just take tiny strips of chow and place them as close to the eggs as you can without smothering any. If you see any stray hatchling silkies you can take a small painters brush and move the strays onto the food. If you want to you can also just move all of the silkies as they hatch into an entirely different container and place your food there with them. Use a small paint brush to gently move the tiny silkies so as not to injure them.

Check on your hatchlings often to look for any strays or to see if you need to add any food. An important thing to look for is any mold that may develop. Since the eggs and hatchlings will be in a humid environment it is important that you keep a close eye on the food and that it does not become moldy. If you notice any mold simply take the container out of the humid environment and let everything completely dry out. When you notice you need to add food is a good time to take the container out for a few hours and let everything dry just to be on the safe side. Usually you will need to add food about 3 days into hatching but probably not much sooner than that. The tiny silkies do not eat a whole lot when they are this small and the strips are usually covered with a layer of silk and frass(waste) instead of being fully consumed. Keep in mind it may take several hours for this silkie, frass covered food to dry completely but it is important that it does dry out to prevent the formation of mold.

I use this routine until the worms are about 3/8" long then I move everything including the Petri dish into a new container where the silkies will spend the rest of their lives until they cocoon. This container is kept at room temperature or sometimes I will provide a heat source if I want my silkies to grow faster for some reason. If you want you can move the silkies themselves with a paintbrush to free up your Petri dish. From here, until the silkies are near the stage where they cocoon, follow the care information at the top under Basic Care.

It's Cocoon Time!

How will you know when your silkies are getting ready to cocoon? Well it can be tricky at first but soon you will be able to recognize your silkies behavior and appearance change when they are ready to spin their cocoons. First the silkworm will stop eating and be moving it's head in a figure eight fashion. What it's doing is beginning to spin a cocoon but sometimes they will get confused and begin eating again when in this stage. Next the worm will have one more defecation that will be really runny and not look like any other frass it has expelled before. It is getting rid of any waste to prepare for mutation. At this point the worm will not begin eating again and needs to be given access to a place to cocoon. You will also notice the silkie will actually shrink and become a yellow color that is somewhat transparent. Now the silkworm is full of saliva(silk) and again needs a place to spin it's cocoon. If you are unsure about being able to recognize when your silkies are ready to spin there's an easy way to make sure you don't wait too long. What you can do is have a new container ready with your cocoon setup but don't use the whole container. Save a small space you can place the biggest silkworms into and continue to feed and when they are ready to spin they will find the area you have set up for them to make their cocoons. What is that setup like you ask? Well it's relatively easy to setup an area for your silkies to cocoon.

The basic requirements for a cocoon ready setup include some sort of configuration where there are plenty or corners or walls where your silkies can attach their cocoons. This material needs to be something that holds the silk like cardboard(not the shiny kind). There are unlimited ways you can accomplish this setup. I have used strips of cardboard bent into many angles and wedged into the spinning container and that has worked well but my preference is to use empty toilet paper rolls. I feel it is the most efficient way in terms of the amount of space that is used.

Take your toilet paper rolls and cut them in half, lengthwise. In your container place these halves so that if you look down upon them it looks like you're looking through a wine rack. Basically you'll be looking at a bunch of circles. To help give support, take paperclips and clip the edges of some of the rolls together to give them stability. This stability is extremely important because once your silkies have started to spin their cocoons, if you make the slightest disturbance, unless the cocoon is almost finished, the silk worm will have to pick a brand new spot and start all over spinning it's cocoon. They're funny that way. Hopefully if this happens the silkie has enough silk stored up to finish a new cocoon. If not the silkie will just die in a half finished cocoon and you'll get nothing out of it.

It will take anywhere from 3-6 weeks for the moths to begin to emerge form the cocoons. After the cocoons have all been spun, if you want, you can remove the cocoon from it's original location and consolidate all of them into a different container. In my opinion this seem to effect the amount of moths that actually emerge as well as it can be a pain dealing with all the small strands of silk. I used to move the cocoons but now I just leave them as is and wait for them to begin to hatch. I always have cocoons that don't hatch and I'm sure you will as well.

Silkie Moths

The moths break out of their cocoons by excreting their saliva, which apparently has a dissolving effect on the silk of the cocoon. For some reason, and I cannot tell you why, a good percentage of moths never make it out of their cocoon. I don't know if this is because there were problems with the silkworm before it began to spin or what. I've tried different temps, humidity, etc. and have never been able to get all the moths to emerge successfully from their cocoons so plan on have some cocoons left that never produce anything. If you want you can take the cocoon to your ear and give it a little wiggle. If you don't feel any movement of anything in the cocoon chances are the moth has been created but cannot get out of it's cocoon. Then you can get a small pair of scissors and cut the cocoon open to let the moth emerge. I would only do this for feeding the moth off to one of my animals. I would not let this moth mate as you may only be passing on defective genes to the offspring. If, when you shake the cocoon, you hear and feel like there's a little marble or pebble in the cocoon it is still in the mutation stage and you should leave it alone.

When a moth does successfully emerge the first thing it might do is hang out until its wings fill with fluid or it may wander around looking for a mate. Males are more likely to wander around than females. When I have a moth emerge I put it into a breeding bin I have set up with small squares of cardboard. Be careful when moving the moths for a couple of reasons. One is that you don't want to injure the delicate wings and also because sometimes the moths will squirt a brown liquid substance from their behinds and it's really pretty gross. Just make sure you've got it's back end facing away from you the first time you move it. Usually the moths will only squirt this material one time. I think it's some sort of hormone but that's really pretty gross. An easy technique I've found to move the moths is to create a small strip of cardboard maybe about 2-3 inches long and ?" wide. Gently coax the narrow piece of cardboard underneath the moths legs. If you're gentle and make small enough movement the moth will eventually just move each leg onto the piece of cardboard. Once the moth is on the strip you can just lay end of the strip where the moth is on one of your cardboard squares so the moth is sitting flat and then with your forefinger push on the moths face away from you while you slide the strip of cardboard from beneath the moth's legs. Otherwise it can be somewhat difficult to get the moth moved without holding it by it's wings, which tend to rip apart easily.

Breeding Bin

What I do to set up a breeding bin is take a Rubbermaid type container that is about the same size as my other bins and place cardboard squares in the bottom. I cut squares of cardboard that measure about 2" x 2" and place them all over the bottom of the container. These squares will be where the moths mate and also where the female moths will deposit their eggs.

As stated above I place new moths into the breeding bin and wait for a male and female to "hookup". A female moth will usually just sit there with some sort of gland protruding from it's behind while the males will be wandering around flapping their wings very rapidly. I'm not sure if I mentioned this but the moths cannot fly. When a male and a female hookup they will be locked at their hind end and may stay that way for days. When I notice two that hookup I take the square of paper they are on and I place the mating pair into a smaller container that allows the cardboard square to lie flat on the bottom. I try to make the cardboard squares just small enough so that they do lie flat. This is so all of the eggs will be stuck to the cardboard and not to the small container itself. I just think it makes things easier in the long run. I just place this smaller container back into the breeding bin. If the female starts to deposit her eggs and the male still has some life left you can take the male out of the smaller container and back into the breeding bin to fertilize another female. Most moths will die after about 6 days and those that last longer might make it one more day but rarely have I seen any moths live past 6 or 7 days.

If you use the technique above the need to recognize male and female moths is reduced. The basic differences between the two are size and shape. The female moths will usually be bigger than the male moths. The female moths will have an organ protruding from their behind that they can retract as well. The male moths are usually smaller and instead of a protrusion have somewhat of a flap on their hind ends. I would suggest you use the method above to start out and learn to recognize the differences if you need to.

The female will lay anywhere from 200-500 eggs on the cardboard or whatever else you may be using. Once the female moth is done laying her eggs she soon dies. If you are planning on feeding the moths to your pets I suggest you wait until the female has laid all of her eggs. This is because I have seen undigested silkworm eggs in the feces of animals I have fed these moths to and I believe it presents an impaction risk. The males you can feed off whenever, once you are able to recognize them.

Eggs

When the female lays the eggs they will be yellow in color. If the eggs are infertile they will remain yellow but if they are fertile they will begin to change. At first they will become somewhat burgundy or brownish in color. After a few days they should turn darker until finally they will be a real dark gray to black color. I seem to notice a hint of purple as well. When the eggs reach this color it is time to put them into the fridge. I take a Ziploc baggie and just put the card with the eggs stuck to it into the bag and then I place that bag into a bigger Ziploc where I store all of my back stock of eggs.

There is some controversy as to whether it is necessary to cool the eggs down before you attempt to incubate and hatch them. Frankly I've seen them hatch even if they skipped the cool down period but I've also seen them fail to hatch without a cool down period. Rarely do I have any eggs that do not hatch if they've been cooled so I would say your best bet is to put them in the fridge for some time before trying to incubate them. I believe there is a much better chance for success if they are cooled first. How long should they be cooled? Honestly I have not kept that detailed of records as to how long they were cooled before I pulled them out to hatch so I can't comment on that. I can tell you with me it's usually been a minimum of a few weeks before they have been brought out to hatch. Supposedly the eggs are good in the refrigerator for up to 5 years.

When you're ready to start a new colony take a batch of eggs out of the fridge and begin to incubate them. That's pretty much all there is to breeding except for one particular problem I have every once in a while and have had no luck figuring out what causes it. After the eggs are laid, if they're fertile, they're supposed to go from yellow to brown then to dark gray or black. This is when you're supposed to put them in the fridge. For some reason I sometimes have eggs that just won't cooperate and skip the change from brown to dark gray/black. These eggs go from yellow to develop a small black dot towards the edge of the egg and then go straight to light gray and hatch!! One time I had this happen unexpectedly and I had thousands of baby silkies I hadn't intended to hatch yet. I wish I could tell you how to prevent or maybe even provoke this to happen but I can't seem to find a constant factor that is different from normal.

I'd like to point out again that the information above is only what I have found works well for me and should only be used as a guide. If you follow some of the basic requirements and watch out for things like mold you very well may find a different technique that works better for you. Also, I am always interested in new ideas so if you have a technique that works well please feel free to share it with me. My username in The Reptile Rooms is wideglide and I'm always willing to answer any questions as well. I hope this information has helped you become successful raising and/or breeding silkworms.

Part 1 of this article - "Raising & Housing Silkworms" - is available by clicking here. http://www.reptilerooms.com/Sections+index-req-viewarticle-artid-100-page-1.html

Article by Rob Talkington. Copyright Rob Talkington ©2005. Reproduced with Permission. All images Copyright The Reptile Rooms ©2005 Unless otherwise stated.