Abstract: Background and Objective: Termites have been classified into morphology-physiologically distinct castes that have a broad range of diets. In this study, the candidate of wood-feeding and fungus-growing termites was chosen to examine the relation between gut morphology, the density of microorganisms and starch hydrolyzing enzyme. Materials and Methods: The gut morphologies of the soldiers of wood-feeding (Globitermes sulphureus (Haviland, 1898), Microcerotermes crassus (Snyder, 1934) and fungus-growing (Macrotermes annandalei (Silvestri, 1914) and Odontotermes feae (Wassman, 1896) termites were determined and compared with those of the workers. Results: No significant differences were observed in the morphological structures between the soldiers and workers in different species. However, the microbial cell counts in the guts of the fungus-growing termites were 3-fold higher than those in the wood-feeding termites, with the hindgut having the highest number of microbes. In the wood-feeding termites, the workers and soldiers harboured a similar number of microorganisms, whereas, the workers of the fungus-feeding termites had 3-fold higher levels of microbes than the soldiers. The enzymatic activity of α-amylase in the fungus-growing termites was dramatically higher than that in the wood-feeding termites. However, there were no differences in enzyme activity in the gut segments of the wood-feeding group and the fungus-growing group. Conclusion: Taken together, the different feeding behaviour and castes of the termites affected the density of symbionts in their gut and α-amylase enzymatic activity was modified according to the amount of nutrition in their diets. This study provided additional information on the hidden role of microorganisms in starch metabolism in the termite’s gut.