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Let's say that there is a large silkworm species, their body being about 70cm (about 2.3ft) in length. Other than their abnormal size, they are just regular silkworms (except for needing much food, of course). They are domesticated and mostly used for producing silk. Assuming that the people that domesticated these worms have silk weaving technology/craftsmanship similar to that of ancient China (let's say about the 4th century), would silk prices be significantly cheaper?

I would like to design silk clothes for characters that aren't high-ranking officials (but not peasants), and I was wondering if that would be possible if there were giant silkworms. A couple of things that might be a problem, though, would be if the silk-making process was the expensive part, if giant silkworms wouldn't be able to produce that much silk, or if their silk would be thicker and harder to work with.

I'm looking for a biologically accurate answer. So if some aspects makes the giant silkworms or their produces impossible, I would appreciate it if that is pointed out in the answer.

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  • $\begingroup$ Under normal silk production procedure, you kill the pupated silkworms to harvest the silk. Are you suggesting a different silk-harvesting method here? $\endgroup$
    – notovny
    Oct 17, 2021 at 11:12
  • $\begingroup$ @notovny I completely forgot about the killing-the-worm part... Thanks for letting me know. I don't really think this would be a problem, though, because they could just let one worm grow up into a moth and it could lay hundreds of eggs. But if this is actually a problem, would extracting some silk from the cocoon (just enough that the worm doesn't die; since the cocoon must be huge) work? $\endgroup$
    – Yellow
    Oct 17, 2021 at 11:31
  • $\begingroup$ @howler extracting the silk involves boiling the cocoon in water (to dissolve the 'glue' holding the threads), so no you cannot have your silk and your worm both. When it hatches, it dissolves a hole in the cocoon, which also ruins the silk. $\endgroup$
    – PcMan
    Oct 17, 2021 at 13:19
  • $\begingroup$ It seems like the square-cube law means that you get less silk per kilo of silkworms if the silkworms are larger, but it's also going to take less mulberry leaves per kilo of silkworm to feed if they're larger, from economies of scale. It's likely more labor to deal with a lot of small cocoons than one big one, per kilo of harvested silk. $\endgroup$
    – notovny
    Oct 17, 2021 at 13:49
  • $\begingroup$ Silkworms are just a device for converting mulberry leaves into silk. The limitations on silk production have always been the availability of food for the worms (they are very picky) and the availability of space (they need to be kept is a stable, balmy environment). Before the invention of reeling machines, the availability of workforce to reel the filaments into yarn was also a limiting factor. Having the giant worms produce thicker filaments would be an advantage. (Silk filaments as they come off the cocoon are about 0.015 to 0.020 mm thick, way too thin to be used as is.) $\endgroup$
    – AlexP
    Oct 17, 2021 at 14:35

2 Answers 2

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So I believe it would depend on the species of the silkworm, as well as other things.

Since you want to use silkworms to make clothing for important people, but not super important people, then maybe just make the silkworms into two different species. Maybe they were originally one species of silkworm but a genetic change appeared and caused some silkworms to grow in size. Scientists studied the silkworms and declared that they had split into two different species, you can also change an aspect of the larger silkworm's silk if you want. You can call the small silkworm silk "old silk" and the larger silkworm silk "new silk." Like perhaps the new silk isn't as soft or it breaks easier, and only important/wealthy people would be able to tell the difference between the two.

Higher ranking officials would probably not want to change and use the new species' silk, so they stuck with the "old silk." This would cause the "old silk" price to only be afforded by the extremely rich. "New silk" would still be expensive, because it's made the same way as "old silk," but it wouldn't be as expensive and it could be used by lesser wealthy/important people!

I hope this helps! :)

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How elitary is silk ? Is there sufficient demand ?

Ok, there we have real silk, 10x the price of fake silk. .. and still, both products are around in abundance and very popular. There is a considerable market for real silk too.

Having passed that one, we can conclude there is demand and a good price, the first questions to answer: is the price of raw silk, or silk coccoons actually relevant for the price of consumer goods ?

First, I need to debunk something,

No need to worry about excessive labour costs

There exist production lines for silk. One of these machines is this one from China, 50k and you're in

enter image description here https://textilemachinery.en.made-in-china.com/product-group/vqlQdWJUsrYA/Silk-Quilt-Production-Line-1.html

Price of coccoons is indeed relevant.. in Japan

Price really depends on the market, in case of silk. A common, true silk Kimono will set you back 300 to 500 dollars in Japan, and 500 to 1500 dollars in the US, depending on quality.

It takes 4000 silk worms (larvae of a moth) to produce a Kimono. Don't buy them online in small quantities, there are a lots of hobby shops with galactic prices.

Silkworm cost.. better to say coccoon cost has been low in China for some years now, 53 dollars per kilogram. As one coccoon weighs about 2 grams say 500 coccons/kg, you'll have your 4000 silk coccoons for about 425 dollars, which approaches the price of an average silk Kimono in Japan. Conclusion: coccooon cost does matter ! When you dont want to farm the larvae and feed them, before getting your coccoons, there is very little margin in Japan. In the US, it may work. In any case, the silk coccoons are a (very) relevant part of the silk price.

Mulberry leaves

Large part of the silk cost price is related to Mulberry leaves. In terms of cost price, our Kimono requires 400kG, which is about 100 dollars cost price in India, a minimum of 25% of coccoon value is leaves. This is expensive food.

Does coccoon size matter ?

A larger coccoon will yield longer fibers. That is good. But thicker fibers may not be appropriate.

In one of the comments, the square cube law was mentioned by @notovny. A coccoon is hollow, when the animal has a larger volume, your area yield lags behind. This is only partially true for coccoons. A coccoon will need to be thicker, to carry the weight - hanging - when the animal is heavier. Larger moths will produce larger and thicker coccoons. But they will also need more food !

Bigger moths and coccoons impact on traditional production

Keep in mind silk has a production history of thousands of years, and the silk coccoons are for a large part still produced in the traditional way. Introducing coccoons 10x current size would require manufacturs to change a long proven technology. Introducing moths 10x current size will have even more impact, facilities need to be upscaled, particularly when coccoons are produced inside the factory.

Conclusion

There is demand, cheaper production could lower consumer prices as well. Production cost of coccoons is relevant for prices in Asia, coccoons make up large part of the price of silk cloathing in Japan.

But I think the answer to the size question is "no". A larger silkworm will either not, or negatively, impact the price of coccoons, calculated per kG of Mulberry leaves. Sizing up the silkworm isn't worth the trouble.

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