Today I'd like to feature one item from the Benton County
Historical Museum's Horner Collection. At the time the Horner Museum began, one
of its goals was to assemble a large collection of natural history artifacts
which would be of use to students in a number of disciplines. However useful
they may have been to students, some of these items do not display well. Many of the shells are very small and would
be hard to see in an exhibit space, for example. So it's nice to be able to feature one item
from the collection here.
The items in the photograph above are silkworm cocoons from
Thailand. These cocoons are the source of the fibers used to make silk
fabrics. The silkworm moth (Bombyx mori)
lays eggs which hatch after about 14 days.
The larvae then feed on their preferred food-- the leaves of the white
mulberry. They eat continuously for
about 42 days and enter the pupal phase by spinning a cocoon of fibers produced
by their salivary glands. If humans do not intervene, the silk moth develops
within, produces an enzyme which eats a hole in the cocoon, enabling the moth
to emerge.
Humans began cultivating the silkworms in China about 5,000
years ago. They provide the mulberry
leaves and collect the cocoons. Before
the moth can emerge, humans would immerse the cocoon in hot water to kill the
pupa within and to soften the cocoon. Then, the filament which makes up the
cocoon is unraveled. The individual
thread is incredibly fine (.0004 inch in diameter) and stretches an amazing 1,000
to 3,000 feet long!
The filaments are so fine that several must be twisted
together to create silk thread which can then be woven into silk fabric. The sheen or shimmer characteristic of silk
results from the prism-like structures of the filaments. It takes about 2,500
cocoons to make one pound of silk!
The production of silk began in China and eventually spread
to Japan and westward, eventually reaching Italy and France. Disease and the development of synthetic
fabrics brought an end to silkworm cultivation in Europe. Today, China is the
leading producer of silk; India is the second largest. Thailand, where these
cocoons come from, is the fourth largest producer.
By
Martha Fraundorf, Volunteer for Benton County Historical Society, Philomath,
Oregon
