The economically important sericigenous insect A. assamensis from NE India is reared on two tree species of the Lauraceae family, Litsea polyantha and Machilus bombycina for its golden yellow, lustrous cocoon silk. Using various enzyme substrates, their natural and synthetic inhibitors in spectro-photometric and fluorogenic assays, we demonstrate that this Lepidoptera uses larval midgut serine proteinases viz. trypsins and chymotrypsins, to digest ingested leaf tissues from either host plant species. Gelatinolytic zymograms clearly indicate that multiple enzymes are active in the midguts of larvae feeding on either host plant species and that some of these enzymes are susceptible to heterologous plant proteinase inhibitors. Preliminary results suggest that the midgut digestive enzymes active in larvae feeding on L. polyantha differ from those found in larvae feeding on M. bombycina, indicating that host plant ‘choice’ affects the digestive physiology of this insect. This result has potential implications for silkworm rearers.