The quantitative and qualitative changes of bacterial flora associated with the silkworm (Bombyx mori) at different stages of its life cycle were studied. Larvae reared on mulberry leaves were dissected and their bacterial populations counted after a 3-day incubation period at 28 ± 2°C. The results showed a higher heterotrophic bacterial population in the fourth and the fifth instars, which coincide with the active feeding stage of the larvae. The similarity of the genera observed in the digestive tract and that observed on the leaves fed to the larvae suggests colonisation of food microflora in the gut following ingestion. The bacteria inhabiting the gut of silkworm were found to be elaborating amylase, caseinase, gelatinase, lipase and urease. The highest percentage of isolates were protease producers followed by lipid and polysaccharide splitters. The results indicate that the bacterial flora play an important role in the digestion of ingested food material.
