(Our 2008 visit to Assam in search of three types of silk.)
When we were getting ready to visit Assam we pulled out our boxes of slides and photographs and reviewed what we learned in Orissa ten years ago. We found eri then, including the marvelous specimen at the top of the page. Unlike tussar, eri is fully domesticated. To understand why eri is so special we need to talk a little about the process of reeling silk. The process is fairly strightforward. The cocoons are placed in warm water to loosen the gum (sericin) that holds the filaments together. One strand of silk is incredibly thin and would be too weak for most textiles, so the filaments from several cocoons are combined. As they are reeled the sericin acts to bind the multiple filaments into a single thread.
When the adult moth emerges from a cocoon it needs to make a hole to get out. The cocoons from which adults emerge are known as "pierced" because of this hole. The hole cuts so many of the fibers that the silk from pierced cocoons cannot be reeled. The silk is still used, but it is spun like cotton or wool and forms a lower grade of silk.
Eri is unusual in that it is never reeled. The fibers in the coccoon are like a tiny bale of cotton, all wound together and tangled. So instead eri silk is spun and this gives it a very unusual quality. Depending on how it is spun and woven it can give a very woolly result - and as with poorly made wools, eri can pill like cheap acrylic. But it can also give a tight strong fiber like linen. This is what makes eri textiles amazing - they can have the drape and weight of linen but are warm and insulating like cotton or wool.
Because eri silk is spun and not reeled it is not necessary to "stifle" or kill the pupa. You can let the moth emerge to mate and lay eggs - or you can eat it for supper. In eastern India eri was (and still is) raised as a source of protein with the silk being a very useful by product.
"Ericulture is a small scale industry in all the three stages; such as, rearing, spinning and weaving, the rearers growing a patch of castor (Ricinus communis) or ‘Kesseru’ (Hereropanax fragrans) plants in their hutments for making use of the leaves for rearing the worms for production of cocoon that is spun into yarn – the yarn woven into cloth by themselves for personal use. Most important however is the chrisalid which is devoured avidly. In fact, eri cocoon is considered a by-product, so also the castor seed. Castor plant is mainly used in other parts of India for production of seed which as a valuable material; but in N.E. region because of its profuse vegative growth and poor yield of seeds, the leaves are utilized for production of eri cocoon only." - Chowdahury 1991.
When we visited Orissa, we noticed that the eri were placed on special baskets when they were getting ready to spin. The basketry provided a perfect environment and permitted easy collection of the silk. Here you can see many cocoons and recently emerged moths.