Silkworm (Bombyx mori)


Silkworm production began over 5000 years ago in China.  The silk spun by silkworms (Bombyx mori) is woven into some of the most beautiful fabric in the world.  The beauty and luster of silk made it the exclusive possession of royalty in China.  The secrets of silk production (sericulture) were closely guarded by the Chinese for thousands of years.  Not until the eleventh century did European traders manage to steal a few eggs and carry them to Europe to begin silkworm rearing.  Since that time, Japan has become the leading producer of silk because the climate is conducive to the commercial growing of mulberry trees (the sole food of silkworms.)  Silk has a commercial value of 340-500 million annually.  Each cocoon a silkworm spins is composed of a single thread, and it takes nearly 3000 cocoons to make one pound of silk.

Availability: These need to be ordered and will be available after spring break.

Housing: You will receive silkworm eggs that you should keep in a petri dish.  Hatching will begin in two to three weeks.  Eggs will turn dark just before hatching.  Move hatchlings immediately with a paint brush to either fresh leaves or diet.  You can also add a small scoopful of food to the dish right next to the larvae, just add more scoopfuls as they are needed.  Feed them immediately after hatching.  Raise your silkworm in a perti dish.  A 9 cm dish works best.  Place a piece of filter paper in the bottom of the dish and moisten it (use a spray mister if possible) so that it is damp but not soggy.  If usuing diet, replace the food as soon as it starts to look dry, moldy, or crusty (roughly every two days), if using leaves, replace the leaves every day.  Young larvae should be kept at 84 degrees F. and 8 hours of light, not sunlight as that may cause them to overheat.  The temperature should not drop below 68 degrees F.  About four days after hatching, the larvae undergo their first molt.  They become somewhat brighter in color and stop eating.  After the first molt, wash out the petri dish and replace the filter paper.  Do this for the second molt as well.  As the larvae grow they require more room and food, and should be separated after the third molt.  The later instars should be maintained at 77-81 degrees F.  Set up more petri dishes as needed to prevent overcrowding.  Check often to insure that all larvae have food and that the food is still fresh.  During the sixth to eighth day of the fifth instar, the bodies of the silkworms shrink slightly and become somewhat transparent.  This indicates that the silkworms are ready to spin their cocoons.  Construct cocoon nests from paper towels or newspapers - or cellophane paper if you want to watch cocoon formation.  Make a roll of the paper, twist one end, put two or more larvae in it, and twist the other end closed (like a Tootsie Roll).  Store the rolls in a dark room at 77 degrees F.  A mature larva needs about three days to spin its cocoon.  Once the cocoon is completed, it takes another two to three days for the larva to pupate.  When you are sure pupation is complete, you can remove some pupae from their cocoons for observation.  To do this, cut open the end of the cocoon with a razor blade and gently extract the pupa.  The females are larger than the males, and their next-to-last abdominal segment has a vertical interruption.  Return the pupa to their cocoons.  If they have been carefully handled, they should still emerge as adults.  Adults will begin emerging about two weeks after cocoon formation.  They tend to emerge in the early morning.  The females are larger and less active than the males.  The males flutter their wings (neither sex can fly) and crawl about in search of females.  Pairs can be kept in clear plastic or glass containers, jars work well.  They will copulate for several hours.  The females will lay eggs on wax paper within 24 hours of successful copulation.  Adults do not feed and live only a few days.  The eggs will require a lengthy diapause before hatching.  Total life cycle should be: first instar, 4 days; second instar, 3.5 days; third instar, 4.5 days; fourth instar, 6 days; fifth instar, 8 days; prepupa, 5 days (total larval time, 31 dyas); pupa, 10 days, adult, 5 days.

Food: Silkworm larvae feed on the leaves of the mulberry tree and will not eat any other food.  Young larvae require young leaves, as they are less tough than older leaves.  You must make sure the leaves are pesticide-free before giving them to the larvae.  If you do not have access to a mulberry tree, there is a mulberry diet we can provide you to feed your larvae with.