Silkworm Rearing

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Silkworm Needs

Natural Food
Rearing Habitat

  • Petri dishes or pint size containers
  • An aquarium or wide mouthed jar with a lid
  • For larv¾: A food plant vase made from film can or 1/2 pint container with "x" cut in lid
  • Pruning shears or heavy scissors are helpful to gather plant material
  • Laundry bleach (sodium hypochlorite)

Food
The natural food plant of the silkworms is the mulberry tree (Morus sp.). Make sure you have a dependable source of pesticide free mulberry leaves before beginning this project. Before feeding the leaves to the larvae, soak the leaves for three minutes in a cleaning solution (three tablespoons of laundry bleach and a drop of dish washing detergent in a gallon of water). Thoroughly rinse the leaves in running water and shake off excess water. Store the leaves in a plastic bag in the refrigerator. The first through third instar larvae require young, tender leaves of mulberry. Offer a leaf in a petri dish and change the leaf daily. After a week you will need to supply more than one leaf. A small piece of damp paper wrapped around the end of the leaf will prolong the freshness. The fourth and fifth instar larvae will need more room and can be set up in the gallon jar with a container to hold mulberry stems and leaves. These older larvae can eat older mulberry leaves. Recut stem ends and quickly insert into water when changing the food plant.

Water
Larvae do not need water if the natural food plant is used because they can obtain all the water they need from the plant.
If you cannot obtain the natural food plant, you must use the artificial diet. See below.

Arificial Food
Rearing Habitat
  • Disinfected glass petri dishes
  • Filter paper or paper toweling
  • Spray mister
  • Circular sheet of paraffin paper which fits inside the petri dish
  • Enough artificial diet for each larva instar
  • Alcohol to reduce fungal growth on artificial food.

    Food

  • Complete instructions should be provided with the purchased artificial food. The following information is gleaned from the Carolina Biological Supply Company informational sheet.
  • First instar larva: Dip one bar of diet in water and remove when the water is absorbed. Remove excess water with paper towel. Place a moist piece of filter paper or paper towel in the bottom of the petri dish and cover with a sheet of paraffin paper. Place the moistened diet on the paraffin paper and transfer the larvae. Cover the diet and larva with a sheet of paraffin paper. Check the diet daily and add drops of water to keep it moist.
  • Second and Third instar larva: After four days, the larva will stop eating and molt. After molting, clean and disinfect the dish or use a new sterile dish. Use the same setup without the moist filter paper. The third instar larva will need at least two petri dishes and will eat at least two bars of diet.
  • Fourth and Fifth instar larva: Make sure the larva have enough room and provide additional petri dishes as needed. The top sheet of paraffin paper is no longer needed. Continue to check the diet and keep it moist. If mold appears, remove the larvae and add one or two drops of disinfectant alcohol. Allow the alcohol to evaporate and reassemble setup.

Water
The artificial diet must be moistened with water before the larvae can eat it.

Taking Care
Cleaning

  • Frass (droppings) needs to be removed frequently to discourage mold. Gently remove the water container and dump out the frass. Every time you change the food plant, rinse out the container and thoroughly dry it. Periodically wash the water container for the food plant.
  • Replace the filter paper and paraffin paper every time you give the larvae new artificial diet. Sterile petri dishes are strongly recommended to reduce fungal growth.

Raising Young
Newly hatched larvae can be transferred by using a small paint brush. Older larvae can be gently picked up with your hands. When the fifth instar larva begins to shrink (after sixth to eighth day), prepare a cocoon nest. Using cellophane paper or paper towels, make a roll of paper by twisting one end and placing two or more larvae in it. Twist the other end closed. Store the rolls in the dark at 25°C (77°F). It takes the larva three days to spin the cocoon and then two to three days to molt into a pupa. By cutting the end of the cocoon, a pupa can be gently removed from the cocoon for examination and returned to the cocoon after observation. Although the adults do not fly, the moths have delicate wings that can be damaged by handling.

If you ordered silkworm eggs, the eggs should be placed in a petri dish. After seven days, the eggs will begin to hatch and continue for one to two weeks. Once the first eggs have hatched, check the dish every day for new hatchlings. A day or two before hatching, the egg will darken around the edge. Transfer newly hatched larvae with a fine paint brush to artificial culture or food plant. If adults copulate in captivity, the female will lay eggs within 24 hours. These eggs will not hatch for some time and can be stored.

Other Concerns
Precautions

  • If you commit to feeding the caterpillar mulberry leaves, make sure you can obtain plenty of leaves. Once the caterpillars have eaten leaves they will not eat the artificial diet.
  • Try to maintain the temperature between 68°F to 86°F especially during the first three instars. If you have access to an incubator, keep it at 84°F (29°C). The later instars can be reared with or without an incubator.
  • Do not place the rearing container where direct sunlight will hit the container. The larvae can easily overheat and die.

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Lesson Plans Information Sheets Rearing Sheets Bibliography
Center for Insect Science Education Outreach The University of Arizona
Contact:CISEO
http://insected.arizona.edu
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