Silkworm Information

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Phylum, Arthropoda; Class, Insecta; Order, Lepidoptera

Identifying Features

Appearance (Morphology)

  • Larvae are worm-like with a short anal horn.
  • Three distinct body parts: head, thorax, abdomen
  • Adult has four wings covered with scales

Adult Males and Females
Adult moths have creamy white wings with brownish patterns across the front wings. The body is very hairy and the wingspan is about 50 mm. Adult females are larger and less active than males. Male moths actively crawl around looking for females. They will copulate for several hours.

Immatures (different stages)
Lepidoptera are holometabolous, therefore they have three distinct morphological stages; larva, pupa and adult. After hatching from the egg, larvae go through four molts as they grow. During each molt, the old skin is cast off and a new, larger one is produced. The silk worm larval life is divided into five instars, separated by four molts. Three pair of short, jointed legs with a single claw at the tip are located on the three body segments immediately behind the head. Five pair of fleshy protuberances (prolegs) ending in a series of hooks called crockets are located posteriorly and ventrally on the abdomen and aid the larva's clinging a climbing abilities on plants.

Natural History

Food
Silkworms natural food plant is the mulberry tree (Morus sp.). An artificial diet has been developed to facilitate cultivation of silkworms. If you do not have a mulberry tree available, you must purchase the artificial diet.

Habitat
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, although presumably old relatives exist in Asia.

Interesting Behaviors
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.

Collecting Live Insects

Where to find
Silkworm eggs and artificial diet can be purchased from Carolina Biological Supply Company and Ward's Biology. Check with other teachers and your district to see if there is a resource person in your community with eggs.

Silk Industry

History
The coveted secret of silkworm cultivation began 5000 years ago in China. Sericulture (the production of raw silk by raising silkworms) spread to Korea and later to Japan and southern Asia. During the eleventh century European traders stole several eggs and seeds of the mulberry tree and began rearing silkworms in Europe. Sericulture was introduced into the Southern United States in colonial times, but the climate was not compatible with cultivation.

Today
Today, silk is cultivated in Japan, China, Spain, France, and Italy, although artificial fibers have replaced the use of silk in much of the textile industry. The silk industry has a commercial value of $200-$500 million annually. One cocoon is made of a single thread about 914 meters long. About 3000 cocoons are needed to make a pound of silk.

To gather silk from cocoons, boil intact cocoons for five minutes in water turning them gently. Remove from the water and using a dissecting needle or similar tool, begin to pick up strands. When you find a single strand that comes off easily, wind the silk onto a pencil. Several of these strands are combined to make a thread.

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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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