Ericulture is mainly confined to North-Eastern region of India accounting nearly 98% of eri silk produced in the country. Eri silkworm is polyphagous in habit and acclimatized to hardy climatic zones of dry lands. The availability of food plants in various states of the country has opened new vistas for the development of ericulture. An attempt has been made to work out the bio-energetics of selected eco-races of eri silkworm in relation to castor varieties. Total food consumption and digestion differed significantly among the castor hybrid/ variety and eco-races of eri silkworm. Highest total food consumption was registered when Borduar eco-race of eri silkworm was reared on the leaf of DCH-177 hybrid both on fresh and dry weight basis. Further, significantly higher mean consumption index and approximate digestibility were observed when Borduar eco-race of eri silkworm was reared on the leaves of DCH-177 castor hybrid on fresh weight basis, while it was significantly more in DCH-177 × Khanapara on dry weight basis. Mean growth rate was differed statistically between the castor hybrid/ variety and eco-races of eri silkworm and significantly more growth with DCH-177 × Borduar on fresh weight basis and DCH-177 × Mendipathar on dry weight basis.