Studies on structural and fibre quality characteristics of eri silk cocoons in different seasons and places

Maximum mature larval, cocoon and shell weight were observed during winter season followed by spring and autumn seasons of both white and brick red eri cocoons. Cocoon weight and shell weight were found about 40 and 5%, respectively, as compared to mature larval weight. Degumming loss was estimated at about 10% for white eri and 12% for brick red eri cocoons. Weight of silk fibres varies significantly between layers and decreasing trend was noted from outer to inner layers. Similar trend was observed for single fibre denier and it differs significantly between places (ecoraces), seasons and layers of cocoons. Ascending trend for single fibre tenacity was found from floss to pelade layers of both white and brick red eri silk cocoons and significant influence was observed for places, seasons as well as layers whereas no impact was noted in case of single fibre breaking elongation. Regression equations between weight of degummed cocoon fibres, single fibre denier and single fibre tenacity and to its corresponding values for different places (ecoraces), seasons and cocoon layers were established and estimated R2 and ‘t’ values confirmed the significance of these regression equations.