The Sacrificial Life of the Silkworm

Silk worm empty cocoons 01

I’ve been thinking about silk a lot lately: about how many silkworms must die in order for us to have our silk.

I had a conversation with the Significant Other’s dad during my recent vacation in Oregon about the production of silk.  I shared what I had read at one point about how silk (for yarn, in particular) was extracted: from the cocoons of silkworm caterpillars.  We watched some YouTube videos on the lives of domesticated (Mulberry) silkworms and silk manufacturing.  A well-filmed batch of 33 pieces of footage is available by Gujo (start watching clip #1), with pleasant tunes and amazing images.

Silk worm 21 days 01

I mentioned that I enjoy the softness and sheen of silk yarn, the smoothness and coolness of silk fabric in general.  Silky yarn can actually be fairly challenging to knit with, especially on aluminum needles due to its slipperiness, which is why I prefer to use bamboo ones instead.  I have made a few beautiful scarves for friends or family (a pink silk one for Yuki and a leafy green bamboo-silk blend for Monica) over the past few years.

I expressed my ambivalence though, on the consumption of silk.  While common animal sources of yarn do not necessarily harm the creature they are taken from, to extract the silk from the silkworms, the silkworms must die.  Or more accurately, they must be killed.

To gather some wool, we (hopefully humanely) shear the sheep.  The sheep then goes on its merry way, and its fleece grows back.  The angora bunny sits there, molting, while you pluck out loose fluffs of its hair.

Silkworms create a cocoon around themselves after about a month of life.  This process takes about 3 days.  They then await metamorphosis into a moth.  When they are ready, they must secrete some fluid to help dissolve a part of the cocoon, and then exit it.

Bombyx mori sul bozzolo 01

Silk manufacturers raise a gazillion silkworms for the production of silk.  When the time is right, they put the cocoons with the moth larvae inside them in hot water to soften the cocoon and to kill the would-be moths.  They then find an end of the silk fiber, and unravel it from the cocoon onto a reel.  They now have a continuous strand of raw silk.

Silk worm cocoons

Other times, they poke the cocoons with a needle, stabbing the larvae to death.

Chiny Shuzhou tkalnia jedwabiu 08

We can’t wait for the moths to exit the cocoon first, because the cocoon must be intact in order to extract the silk filaments.  Recall that the moth damages the cocoon a bit in order to abandon it.

Some moths are allowed to live in order to lay more silkworm eggs to continue the silkworm breeding process.

One cocoon produces about 1,000 yards of a silk filament.  Several are needed to make a strong, usable strand.  Approximately 1,500 cocoons are needed to generate about a pound of silk.  1,500 little moth larvae must be stabbed or boiled.

The poor little larvees!!  This makes me sad.

To be honest, I’m not a big animal rights activist or anything.  Sure, I care about humanely interacting with animals.  I’d like to think I’m sensible about it.  And yet, the idea that we subject little critters to such a ghastly end to take away their “homes” to clothe ourselves seems callous.  Especially since we don’t have to use silk clothing (although, it’s true we have been doing this for thousands of years, beginning in China..).

(Hmm.. but, on a similar note, aren’t I an omnivore?  Well yes, ’tis true.. but that’s a discussion for another place.)

Alternatively, we can use artificial silk or even wild (Tussah) silk.  I’m not a big fan of knitting with synthetic materials.  Wild silk yarn is apparently coarser then domesticated (Mulberry) silk yarn.  Nevertheless, perhaps I should focus on only buying silk yarn made from wild silkworms.