The results revealed the activity of some digestive enzymes in the anterior, middle, posterior portions of midgut of third instar larvae of Eristalis megacephala and it showed that the highest pH of trypsin was at pH 6 in anterior mid-gut, middle mid-gut, and posterior mid-gut. The highest pH of chymotrypsin in anterior mid-gut was at pH 7, in the middle mid-gut it was nearly similar at all chosen pH values but slightly higher at pH 7 ,while the chymotrypsin activity in the posterior mid-gut of the larval stage of Eristalis megacephala was highest at pH 8.The highest activity of leucine – aminopeptidase was at pH 9 in anterior mid-gut, at pH 6 in middle mid-gut and at pH 7 in posterior mid-gut. The highest pH of carboxypeptidase A in the anterior mid-gut was at pH 6, in the middle mid-gut was at pH 7, while at pH 6 in the posterior mid-gut. The highest pH activity of carboxypeptidase B was 9 in anterior, middle and posterior mid-guts.
          Some glucosidases were studied and it showed that the highest pH of α- glucosidase was at pH 5.6 in anterior, middle and posterior mid-gut .The highest pH of β- glucosidase was at pH 6 in anterior, middle and posterior mid-gut. The highest pH of α- galactosidase was highest at pH 6 in anterior mid-gut and in the middle and posterior mid-gut at pH 5.6 .The highest pH of β- galactosidase was highest at pH 6 in anterior, middle and posterior mid-guts .The highest pH of α – amylase is at pH 3.6 in anterior mid-gut, pH 6 in middle mid-gut and pH 5.6 in posterior mid-gut. The present study also revealed that the activity of acid – phosphatase was high in anterior mid-gut that middle and posterior mid-gut while the activity of alkaline phosphatase was nearly similar in anterior, middle and posterior mid-gut but slightly higher in anterior mid-gut of larval stage of Eristalis megacephala.