Silk. Part I: An Introduction

uttu-textiles.com // Issam Yousef // 20 September 2013

Since my graduation project, in which we studied traditional silk fabrics, my fascination for silk has grown.  I am not talking only about the myths that surrounded the silk production when it was first discovered in China, or the secret that was well kept for 2000 years, or the legendary stories of how other nations stole it and smuggled the silk worms cocoons out of China, no, I am talking about the whole deal, I am fascinated by the spider silk, the scientist attempts to reproduced it and the spider goat and so on.

So this article, obviously, will be about silk.  The article is three parts. Part I is the introduction, I discuss the amazing insects that produce silk.  Part II is the spider silk part, and part III is the bombyx mori silk or the natural silk.

There are few insect that produces silk and only two type of forest pest, defoliators and sawflies.  The defoliator’s larval or caterpillar rise the moth, and the sawfly is the larvae of primitive group of wasps.

The silk is a proteinaceous liquid produced by glands inside the insect, when needed it is transferred to the spinneret by fine tubes, either to the head, where the silk worm spinneret is or to the end of the abdomen, where the spinneret is for spiders.

Silk Producers:

1- Mullbery Silk Worm

The scientific name is Bombyx Mori and it has been domesticated from its wild ancestor Bombyx Mandarina 2700 BC in China.  The larva produces the well known silk fibers in form of cocoons, figure 1.  We will discuss this in details in part 3.

Figure (1): Mullberry silk worms and cocoons, Images adapted from Khalil Moukayes, Tammam Al-Abed and Eman Okasha, The influence of Various Mounting Materials on Production of Silk Worm Bombyx Mori L., Teshreen University Journal for Studies and Scientific Research - Biological Science Series, Vol 28 (1), 2006. p133 - 143. And Martha E. H. Rustad, Silkworms,  Capstone Press, Mankato, 2009
Figure (1): Mullberry silk worms and cocoons, Images adapted from Khalil Moukayes, Tammam Al-Abed and Eman Okasha, The influence of Various Mounting Materials on Production of Silk Worm Bombyx Mori L., Teshreen University Journal for Studies and Scientific Research – Biological Science Series, Vol 28 (1), 2006. p133 – 143. And Martha E. H. Rustad, Silkworms, Capstone Press, Mankato, 2009 

2 – Spiders

Spider produce a very amazing silk, lighter and stronger than steel.  It can take a very large amount of deformations without breaking.  We will discuss spider silk in part II.

Figure (2): Spider web adapted from Jason Plamer, Spider silk spun into violin strings, 5 March 2012, available from http://www.bbc.co.uk/news/science-environment-17232058.
Figure (2): Spider web adapted from Jason Plamer, Spider silk spun into violin strings, 5 March 2012, available from http://www.bbc.co.uk/news/science-environment-17232058.

3 – Sawfly

Similarly to Bombyx Mori, the sawfly larva spin a reddish brown cocoons around the defenseless pupal stage in which they turn into adults, figure 3.

Figure (3): Sawfly cocoons, adapted from http://www2.ca.uky.edu/entomology/entfacts/ef410.asp and from Douglas C. Allen, Insect-Produced Silk: From Textiles to Tents, The New York forest Owner. 37: 6, 1999.

Figure (3): Sawfly cocoons, adapted from http://www2.ca.uky.edu/entomology/entfacts/ef410.asp and from Douglas C. Allen, Insect-Produced Silk: From Textiles to Tents, The New York forest Owner. 37: 6, 1999.
Figure (3): Sawfly cocoons, adapted from http://www2.ca.uky.edu/entomology/entfacts/ef410.asp and from Douglas C. Allen, Insect-Produced Silk: From Textiles to Tents, The New York forest Owner. 37: 6, 1999. 

4 – Other Moths

The Gypsy moths are examples of moths that produce silk.  After the Gypsy moths larva hatch, they disperse using a silk thread like a parachute to ride the strong wind.  Their amazing anatomy (hair) with the silk thread help carry them for miles.  Many other moths depend on this method of dispersing to spread.

Figure (4): Gypsy moth silking on the stones, adapted from http://asia.ansp.org/hovsgol/GEF-WB/research/gypsy_moth.html
Figure (4): Gypsy moth silking on the stones, adapted from http://asia.ansp.org/hovsgol/GEF-WB/research/gypsy_moth.html
Figure (5): Newly hatched Gypsy moth, adapted from http://www2.ca.uky.edu/entomology/entfacts/ef410.asp
Figure (5): Newly hatched Gypsy moth, adapted from http://www2.ca.uky.edu/entomology/entfacts/ef410.asp
Figure (6): A Gypsy moth larva dispersing using the silk threads
Figure (6): A Gypsy moth larva dispersing using the silk threads

Other moths leave a mark trail of silk threads to guide the new caterpillar from and to the nesting place.

Some larva use the silk to build a tent to protect from weather and predators, figure (7).

Figure (7): Silk tent, adapted from Douglas C. Allen, Insect-Produced Silk: From Textiles to Tents, The New York forest Owner. 37: 6, 1999.
Figure (7): Silk tent, adapted from Douglas C. Allen, Insect-Produced Silk: From Textiles to Tents, The New York forest Owner. 37: 6, 1999. 

Other caterpillars use the leaves and the twigs to create a shelter, figure 8.

Figure (8): Leaves turned into shelter by silk, adapted from http://cabinetofcuriosities-greenfingers.blogspot.co.uk/2010/05/ermine-and-silk.html
Figure (8): Leaves turned into shelter by silk, adapted from http://cabinetofcuriosities-greenfingers.blogspot.co.uk/2010/05/ermine-and-silk.html

Although there are many insect in the forest to produce silk buy, unfortunately it is not economical to collect it.  These insects are very hard to domesticate as well, including the spiders.

So as most of the authors of the references below advise, when you see these structures out in the wild, take a moment and admire their great construction and beauty.

References:

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Read this article on our website:

http://uttu-textiles.com/Home/silk_part_1_intro.html

Read this article on our forum:

http://uttu-textiles.com/forums/viewtopic.php?pid=112#p112

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