Seasonal Performance of Eri Silkworm, Samia ricini (Lepidoptera: Saturniidae) in Two Different Zones of Manipur, India

Samia ricini, commonly known as eri silk worm, is a domesticated, multivoltine, polyphagous silkworm which feeds on various food plants, namely castor (Ricinus communis Linn.), kesseru (Heteropanax fragrans Seeman), tapioca (Manihot esculanta Crantz), etc. Among them, castor and kesseru are considered major food plants. This silkworm species is widely reared in various regions of north-eastern states, including Manipur. The seasonal performance of the silkworm in two different zones was evaluated to assess its optimal season for growth, development, and cocoon productivity, as there is limited comparative research on low- and high-altitude conditions of Manipur. The present study was conducted in three different seasons (Spring, Summer, and Autumn) across two zones (Wangkhei and Sanjenbam Hill) of Manipur. To achieve this, variables such as fecundity, hatching percentage (%), larval length, larval weight, larval survival rate, effective rate of rearing, cocoon weight, shell weight, pupal weight and cocoon-shell ratio were studied during Spring (March- April), Summer (May- June) and Autumn (September- October) seasons of 2025. Rearing was performed on the preferred host plant, Ricinus communis (castor). Seasonal variations had a significant effect on some of these parameters, primarily attributed to differences in temperature, humidity, and leaf quality. Two commercial parameters, shell weight and shell ratio, were 0.41±0.03g, 0.33±0.03g,0.33±0.01g, and 13.77±0.59%, 13.52±0.53%, 13.64±0.45% in summer, spring, and autumn of Wangkhei and 0.41±0.02g, 0.29±0.01g,0.30±0.01g and 13.47±0.42%, 13.19±0.78%, 13.65±0.43% in summer, spring, and autumn of Sanjenbam Hill, respectively. This indicates that the summer season was the most favourable in terms of performance and productivity in both zones in Manipur.