Background
Silkworms are the larva of a moth (Bombyx mori) native to Asia that spins a cocoon of fine, strong, lustrous fiber that is the source of commercial silk. The culture of silkworms is called sericulture. The various species of silkworms raised today are distinguished by the quality of the silk they produce. Silkworms feed on the leaves of the mulberries (genus Morus) and sometimes on the Osage orange (Maclura pomifera).
Bombyx Mori will not bite, making an ideal worm for feeding most reptiles, amphibians and other animals, and they offer great nutritional value.
Newborn are small enough for most baby reptiles to eat and young silkworms can even be fed so they will grow to a desired size. Silkworms are soft-bodied, slow moving and can grow to 3 inches in length. They are also relatively fast growing, reaching about 3 inches in length and ready to cocoon in as little as 25 - 28 days.
Silkworms go through four stages of development, as do most insects: egg, larva, pupa and adult. The adult (imago) stage is the silkworm moth. The larva is the silkworm caterpillar. The pupa is what the silkworm changes into after spinning its cocoon before emerging as a moth. Since the silkworm grows so much, it must shed its skin four times while it is growing. These stages-within-a-stage are called instars.
Today, the silkworm moth lives only in captivity. Silkworms have been domesticated so that they can no longer survive independently in nature, particularly since they have lost the ability to fly. All wild populations are extinct. Also contributing to their extinction is the extraordinary fact that they only eat mulberry leaves.
Silkworms have been used by researchers to study pheromones or sexual attractant substances. The pheromones are released by female moths and the males detect the chemicals with olfactory hairs on their antennae. This allows the male to find the female for mating. The male antennae are made of many small hairs to increase the chances of picking up small amounts of the pheromones over long distances.
How to Grow Your Worms to the Perfect Size
The great thing about silkworms is that they only grow as much as you feed them, and they can go for a week or two without food. Say you have a couple hundred small silkworms, but you have a big bull frog or iguana. All you have to do is feed the worms as much as they'll eat, keep them warm and dry, and in a few days, you'll have some good sized worms. Have too many silkworms? Not a problem, feed them once or twice a week and they'll stay alive until you need them without growing much larger.
Wash hands thoroughly before handling the worms or the food or they may develop bacterial problems. Using a cheese grater, grate a small amount of food onto the worms and repeat until the worms reach the desired size. For best results, maintain temperatures between 78° and 88° F.
Excessive condensation forming in the container after feeding is the leading cause of failure. If this condensation does form, take the lid off your container and allow the container and old food to completely dry out. In the future, make sure the previous food is dry before feeding again. Old damp food is a breeding ground for mold and other problems, dry food is not.
As the silkworms grow, you may need to transfer your worms to a larger plastic container. The lid needs to have ventilation holes. If not, you need to vent the lid so the silkworms won't suffocate and to allow condensation to dissipate. You can also use a shoebox. The old food and waste matter can be removed, but does not have to be if it remains thoroughly dry.
Under ideal conditions (78° to 88° F and allowed to feed nearly continuously) silkworms can go from egg to 1 inch in length in about 12 days, and 3 inches in under 30 days. The worms will begin to spin cocoons at about 28 - 30 days old or when they are between 2 1/2 and 3 inches long.
From Cocoon to Moth
Silkworm moths emerge from their cocoons after spending about two to three weeks metamorphosing. As moths, they do not eat or fly. They will usually mate, lay eggs and die within a week. Fertile eggs turn from yellow to gray or purple in a week or so. If the eggs don't hatch within 3 weeks, they usually will not hatch until the following year (see above-from egg to larva).
Proper Handling Procedures
Again, in order for your worms to stay healthy for many weeks, you'll need to keep the silkworms as dry as possible. If condensation builds up during feeding, vent the container lid to prevent excess humidity.
Be sure to wash your hands thoroughly before handling the worms or their food. Silkworms can be susceptible to bacteria if you don't properly handle them. As long as the container environment remains dry, your worms will be fine.
Mold develops from high temperatures and high humidity. If the worms are covered with droppings, silk and old food for too long, mold may develop and kill the worms. If mold does develop, grate about 1/4 inch of food (sold separately) all over the worms with a cheese grater. As the worms crawl to the top of the new food pile you can transfer them off the moldy food and place them into a new container.
Silkworms are susceptible to bruising and dying if not handled with care, especially as they grow larger. When handling and transferring the worms, be very gentle.
Mark Spranger is the owner of http://www.silkwormshop.com and http://www.buyfruitflies.com