Samia ricini is an important non-mulberry silkworm species with considerable nutritional and economic significance in the sericulture industry. In addition to silk production, its developmental stages have potential nutritional value, while Eri culture provides opportunities for income generation and small-scale rural livelihoods. Castor (Ricinus communis) is one of the principal host plants of S. ricini and supports its growth and development under laboratory conditions. However, the seasonal availability of host leaves can limit continuous rearing, highlighting the potential importance of artificial diets. The present study aimed to assess the morphological, developmental, and biochemical characteristics of S. ricini reared on castor leaves and to evaluate semi-synthetic artificial diets for larval rearing. Selected macromolecules were analyzed at different developmental stages, and the breaking properties of S. ricini and Bombyx mori silk fibres were compared. Fifth-instar larvae exhibited the highest soluble protein concentration (6.75 mg/mL) and carbohydrate concentration (4.4 mg/mL), whereas prepupae showed higher ash (3.50%) and crude fibre (2.38%) contents. Larval development was accompanied by distinct morphological changes across successive instars, reflecting the developmental transitions associated with metamorphosis. Larvae reared on fresh castor leaves showed better growth and survival than those reared on the artificial diets, while Diet 01 performed better than Diet 02. The findings indicate that castor leaves remain a suitable host for the growth and development of S. ricini, whereas the artificial diets tested require further optimization to improve larval performance. Nevertheless, the ease of preparation and storage of the diets suggests their potential utility for laboratory rearing and for reducing dependence on seasonal host-plant availability. Overall, the study provides information on the nutritional characteristics, biology, and dietary requirements of S. ricini that may contribute to the development of improved rearing strategies.
