A Comparative Study on the Rearing Performance of Six Strains of Eri Silk Worm Samia Ricini, Donovan in Four Different Seasons.

Abstract

Samia ricini, commonly known as eri silk worm is a domesticated, multivoltine, polyphagous silkworm species which have several morphotypes having distinct morphological differences. This silkworm species is cultured in different regions of North-eastern states specially in Assam. In addition to twenty six different ecoraces, six morphologically distinct strains of Samia ricini have been identified on the basis of larval markings and colour, they are Yellow plain (YP), Yellow spotted(YS), Yellow Zebra(YZ) and Greenish blue plain(GBP), Greenish blue spotted(GBS), Greenish blue zebra(GBZ).The present study was conducted with the aim to evaluate the rearing performance of these six strains of eri silk worm in four different seasons. To achieve this goal Fecundity, Hatching percent, Effective rate of rearing, larval duration and moth emergence and Shell ratio(%) were evaluated in spring, summer, autumn and winter. The study reported significant differences in all these parameters among different strains. The variation among them was significant at P <0.05 significant level. Seasonal variation also have profound effect on these parameters. Summer and winter seasons were reported as unfavorable in terms of performance while spring and autumn can be considered more suitable. Present study revealed that Yellow spotted strain showed highest shell ratio (%) therefore expected to produce more silk. ERR and hatching(%) was highest in GBP and GBS showed highest fecundity in autumn followed by spring. Larval duration was longest in GBS in winter and lowest in GBP in summer. The results revealed that Greenish blue strains -GBP and GBS are better in terms of rearing performance and spring and autumn are the favorable seasons for rearing of all six strains.