How Do We Get Red Eri Silk Cocoons? What Causes The Red Color?

All silks, as you know, are spun from cocoons. The most popular silk, which accounts for 80% of the global market, is Mulberry silk.

We in Muezart are working to promote a regional, special, silk called Eri silk which comes from the cocoons of a moth called Samia Cynthia Ricini. Eri silk is also called peace silk.

Mostly the Eri silk cocoons are white or off-white in color. Did you know that there are red Eri silk cocoons too? Here is a story on how we are learning more about red Eri silk cocoons. 

Nature Weaves Its Magic -  Red Eri Silk Cocoons

We were taken by surprise when we saw different colored Eri silk cocoons when we visited our Eri silk partners in their villages. We saw soft golden colored cocoons in Kong Tharina’s village Pyngkya, in the East Khasi hills district, and saw red colored Eri silk cocoons in village Jirang, in Ri Bhoi district. The best part was that the yarn that they spun from these had the same beautiful color too. So, the fiber in the cocoon had the same color all through. A touch of magic from nature.

Red eri silk cocoons

How Does Eri Silk Cocoon Get a Reddish Color?

What could have caused these reddish colors in the Eri silk cocoons? Is it common or a rare occurrence? Our team set out to explore.

Khraw, a Muezart team member who builds our network of Eri silk rearers, talked to some of them and asked them. Have they seen red Eri silk cocoons? IHow do we get red colored Eri silk cocoons?

He was told that if the Eri silkworms are fed leaves of Sla Paiam (ficus citrifolia), instead of the normal castor or cassava leaves, they will produce red colored cocoons.

The Eri silk rearers said that they had seen cocoons in white, pale white, reddish and soft golden colors. The most common, they said, were the white ones.

Various colors from the eri silk cocoon

Khraw asked our partners whether there was any difference in the quality of the fiber that was spun from a red colored cocoon and a white colored cocoon.  They said they had not noticed any such difference. They said the fibers felt the same.

Here is when this story gets interesting. 

Kong Molina Has Scientific Curiosity - What Causes The Red Color?

Khraw got in touch with Kong Molina, another of our partners, asking the same questions, and guess what?

She surprised Khraw by saying that she had conducted an experiment to check the effects of feeding Eri silkworms a different diet - leaves other than castor or cassava leaves.  Khraw was all excited and this is what he found out:

  • The Eri silkworms were kept in different baskets.
  • In each basket the food for the silkworms was different.
    • In one they were fed sla paiam leaves, in second basket castor leaves and in third basket they were fed tapioca leaves.
  • The results were interesting:
    • Eri silkworms fed with sla paiam leaves produced many red colored cocoons.
    • Eri silkworms fed with castor produced no red Eri silk cocoons
    • Eri silkworms fed  with tapioca leaves produces no red Eri silk cocoons but a few golden colored ones.

Is that not exciting to hear? So, feeding Sla paiam leaves seems to result in red cocoons?


Castor leaf

tapioca leaf

Kong Molina Experiments Further

Kong Molina went one step further – she tracked the moths that emerged from the red cocoons till they laid their eggs. She kept track of these eggs.

The silkworms that came from these eggs were fed castor leaves. From this batch of worms, which were babies of the moths that emerged from the red cocoons, Molina got a few red cocoons too!

Oh my! This is super exciting, is it not? We thought feeding sla paiam leaves caused the color. But, we find that silkworms from moths of red colored Eri silk cocoons produced red Eri silk cocoons too though they were not fed paiam leaves. So, could red color by a genetic thing? 

Red Color is Genetic or Based on Food?

Let us take stock of what we know:

  • Eri silkworms fed with paiam leaves produced many red Eri silk cocoons
  • Silkworms of the moths from these red Eri silk cocoons were fed only castor leaves, but they too produced some red Eri silk cocoons.

Can we conclude that the moths from a red cocoon can give birth to silkworms that can create red Eri silk cocoons even if fed only castor leaves?

So, the coloration is genetic? Or is it a combination of both - genetic and diet?

We do not know for sure.


payam tree

payam leaf

We Will Repeat The Experiment - To See What Factors Produce Red Eri Silk Cocoons

We were Amazed at the scientific curiosity that Kong Molina has.

We are now talking to her to repeat this experiment to see if we get red colored Eri silk cocoons every time the Eri silkworms are fed Sla Paiam leaves.

We want to record what happens at every stage.

Muezart will work with her on it.

Get a closer look at the reddish cocoons in our Instagram post.

Yet Another Interesting Possibility - Polymorphism

While we were putting this story together,  Miranda, a Muezart maker, did online search and found an interesting study which talks of polymorphism as the cause of different colors in Eri silk cocoons. The study says that Eri silkworms exhibit color polymorphism (two colors occur in the same species) – some cocoons are brick red and some creamy white.

So, looks like the red color is purely a genetic thing?

We are not sure, but we will find out. For now, we continue to be fascinated every time we see Eri silk cocoons in nature given shades of red.  

Curious what polymorphism is?

In biology and zoology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species.

Golden rust color of eri silk cocoons

Experiments on How to Produce Colored Mulberry Silk Cocoons 

We found that people are experimenting with feeding dyed mulberry leaves to mulberry silkworms to produce colored mulberry silk fiber. We found it a bit disturbing. Does that not not look unethical? 

The study says:

The technique involves feeding the larvae their favorite food — mulberry leaves — dipped in dye. The dye is transported along the biochemical pathways of the silkworm to produce a colored cocoon and colored silk fiber.

Want To Know The Result of Our Experiment on The Effect of Diet on The Color of Eri SIlk Cocoon?

We will get started on the experiment that we talked about earlier – to check if Eri silkworms fed with Sla Paiam leaves produce red Eri silk cocoons. We will update this post once we are through with a couple of rounds of testing. If you want to know as soon as we finish the experiment then send us that request, as comments along with your email, and we will keep you posted. 

Have you come across red Eri silk cocoons? If you happen to know more about them, do share with us. 


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