The white or brick-red eri silk (endi, errandi) is produced by Philosamia ricini Boisduval, a domesticated multivoltine silkworm. Its culture is widespread in Assam and practiced on a small scale in Bihar, West Bengal, Manipur, Orissa and Tripura. The Fabric made from this silk is valued by the Assamese, especially for the making of chaddars.
Philosamia Boisduval is reported to comprise only one well-defined species. P. Cynthia D. and sixteen forms/variants/aberrants/races. Members of the genus are found in the Palaearctic and Indo-Australian biogeographic regions .Eri silkworms were successfully acclimatized in America and Europe in the middle of the nineteenth century, but could not take firm hold.