By Nabasmita Malakar
Forest of Persea bobycina (Som plant) in Gurmow, Baksa district, B.T.A.D (Assam)
Photo: Nipu kumar Das
The link between human and nature have been intimate right from our very origins even though it might be difficult to observe them today, particularly in our city areas. I belong to a place where even today nature is worshipped and celebrated during all our festivals. Yes, I am talking about the state of India which lies in the south of the eastern Himalayas, Assam. Bihu, the most important cultural festival for the Assamese people, is also the name of our traditional dance. It signifies the coming together of humans and nature beautifully, not only in its rituals, but also in the dance movements, food and adornments of the performers and worshippers. I clearly remember, when I was in the 2nd standard of elementary education, I did my first Bihu performance in a competition held at my school. That was the first time I wore Mekhela-chador (traditional dress of Assam) made of Muga (Muga is an Assamese word which means the colour brown) silk, that Assamese people wear during Bihu dance or festival. I found the dress extremely heavy and asked mom the reason for it. She explained to me with a smile that because of the silk, motifs and fabrics, Muga cloths are always heavy. Since that age, this silk has been connected to my memories and pride of belonging. Though I have been wearing it from a very teen age, way before my research life about Laurel plants of India started, I have to admit that I didn’t know much about the facts behind this silk.
Now, you might be thinking that how Muga silk and my research are connected? Well, for research, my interest was inclined towards the family Lauraceae as the ecological, economical and evolutionary characters made it an interesting plant group. So, I read publications related to laurel plants and to my pleasant surprise I found one interesting article about Muga silk moth and their host plants i.e. Lauraceae plants. I was so excited to know that the silk I was wrapped right from my childhood as a Bihu Nasoni (Assamese phrase of a dancer), has a direct link with my research interest. Is it just a coincidence that the plant family I chose to study includes the main host plants of the most important fabric of Assam and its culture?
If we look back the history, then we will find that from a very ancient period, Assam is known for sericulture industry as it produced three different types of indigenous Silk- golden Muga, White pat and Eri silk. History of sericulture traced back to 2640 BC in China. First weavable silk fiber was discovered by Chinese ruler Xi Lingshi. Silk culture and weaving technology were kept secret for 2500 years from the rest of the world as silk was a valuable commodity for China and they traded to various places of the world. Among all other silk, muga silk is the most expensive silk in the world, compared to being as expensive as gold. Exact time of origin of Muga silk culture in Assam is not clear due to the lack of authentic historical account. It was believed that knowledge of Muga silk culture has come from China and it is flourished in Assam during the period of Ahom dynasty. Ahom regime (1228-1828) is considered as golden era of Muga silk culture in Assam. Earlier it was only confined to royal families but now-a-days it is one of the necessities for every Assamese family.
The insect that produces the Muga silk is known as the Muga silk moth (Antheraea assamensis), and it is found in the Northeast India, Bangladesh and Sri Lanka. Like all other insects, Muga silkworm also goes through different stages of life cycle viz. egg, larva, pupa and adult. Except for the larval period, other stages are the indoor processes. During larval stages, they feed on young leaves of different Laurel plants in wild habitats. When larvae go into the maturity phase, that is the caterpillar spins the case around it with silk thread from the secretions. After this, they prefer to stay between dry leaves. The pre-pupa is soft and light green in colour and gradually it becomes brown, from where silk thread or fiber can be extracted. Silk production from this silk moth only practiced in Assam. The Muga cocoon rearing villages spread across in Lakhimpur, Dhemaji, Dibrugarh, Sibsagar and Jorhat districts. However, the production of Muga silk from Muga cocoons only confined in Sualkuchi, known as textile center of Assam, which is situated at North Bank of the River Brahmaputra. It has a huge number of households engaged in handlooms, for which it is known as “Manchester of Assam''. Here maximum Muga cloth production occurs and is supplied to traders of Assam and beyond.
Muga silk, which always seeks attention and people often ignore the basic demand of the Muga silkworm i.e. about their larval food. Young leaves are the only diet for the Muga silkworm, so it is equally important to focus on conservation of host plants in their wild habitats. Different species of laurel group of plants are the larval food plants of Muga silkworm such as Som (Machilus bombycina) and Sualu (Litsea monopetala) are the primary larval food plants for muga silkworm. Som plants are widely abundant in upper Assam (Dibrugarh, Dhemaji, Sibsagar, Lakhimpur, Jorhat and Golaghat districts) as well as large plantation in the forest and hilly region of lower Assam (Darrang, Kamrup, Karbianglong and Goalpara Districts). Secondary larval plants include Mejankari (Litsea cubeba), Nepali Bonsum (Phoebe lanceolata), Dighloti (Litsea salicifolia), Korpur (Cinnamomum camphora), Tejpat (Cinnamomum tamala) etc. Besides these, other secondary laraval food plant species like Kathalua (Litsea nitida), Baghnola (Actinodaphnae angustifolia), Pati-honda (Actinodaphnae obovata), Gonsroi (Cinnamomum glaucescens) are also good food source for Muga larva.
Machilus bombycina (Assamese name- Som); host plant for Muga silk moth
Photo: Nipu kumar Das
The choices of food of Muga silkworm are restricted to some plant species because they prefer allelochemics such as alkaloids, tannins, terpenoids etc. and the Laurel leaves contain a very high amount of these chemicals. Due to this, the Muga silk moth mostly completes its life cycle on these species. Three major factors of Muga silk moth viz. survival rate, silk production in terms of quality and quantity and fecundity depends upon the host plant. Better the quality of the leaf of the host plant, the greater possibility of getting a better quality of cocoons. People have found that hybrids between Som (Machilus bombycina) with Dighloti (Litsea salicifolia) showed better quality of Muga silk but such practices haven’t been intensified yet. In the present day, there is no regular cultivation of this plant and consequently the Mejankari silk production has also decreased. Digholoti (Litsea salicifolia) is also very suitable for Muga silkworm rearing. Because of its bushy type, it prevents various pests and predators. This plant is utilized only for experimental purposes not yet commercial level. Even many peoples of Assam still unknown about the utility of this plant regarding Muga silkworm rearing. Due to lack of proper knowledge, still many food plants are unexploited commercially.
Laurel plants are mostly evergreen trees, so they love to grow in shady places, high land with well-drained soil. They are mostly found in forests and some plantation areas of villages. In some areas, host plants have been cultivated in the edges of forests for better shelter for silkworm. Though monsoon season (April-August) is considered ideal for planting Muga food plants but people mostly use one tree for two rearing in a year alternately during spring and autumn for commercial purpose. One full-grown tree can yield 1000 cocoons in a year and to acquire 1kg of Muga silk, 5000 cocoons are required, i.e. 5 trees for 1kg Muga silk and that can produce only about 5-6 sets of Mekhela-chador. This calculation clearly showed the importance of their host plants to save the culture as well as economy of the region.
As Lauraceae plants and Muga silk moth are widely found in the Northeastern region, the people of the region besides Assam can involve in producing this high-quality silk and this will help to improve the economic development. It is also important to make people aware of the importance of Lauraceae plants and Muga silk moths for the growth of the economy in NE region of India.
As I mentioned earlier the quality and quantity of Muga silk depends on the host plant varieties and negligence to conserving the host plants, leading to a decrease in the quality and quantity of silk production. This could be one of the reasons why currently the price of the Muga silk shooting high and becoming unaffordable for many peoples, resulting duplicating with other silk and finally endangering the weaving art and Assamese culture. Day by day forests are decreasing due to deforestation and urbanization hence host plants of Muga silkworms are losing their wild habitat. Now-a-days government has taken the initiative to rear the plants in nursery, due to which they are breaking out from their original habitats and that leading to loss of unique genetic flow between them. It is very important to understand that we need to conserve these plant species in their wild habitat to maintain unique characters of Laurel species. Also, due to other economic uses of Laurel plants such as timber, medicines, food etc., people are overexploiting them for their own greed without any conservation strategies that making these species more vulnerable to extinction and leading us to an uncertain future.
The author would like to thank Rajkamal Goswami (Research Associate, ATREE) and R Ganesan (Fellow, ATREE) for their valuable insight in preparation of the article.
About the Author:
Nabasmita Malakar is a Project Associate and Ph.D student in Suri Sehgal Centre for Biodiversity and Conservation, ATREE, Bengaluru. She works on field of plant science focusing on Systematics and Evolutionary Biology.
You can reach her at firstname.lastname@example.org