Insects are excellent models for the study of the intestinal function mainly due to the fact that there are suitable species to almost all types of habitat and food habits.  Moreover, the gut is the biggest interface between insect and environment.  Therefore, an understanding of the digestive process for the development of biological control methods, such as the use of transgenic plants in the control of phytophagous insects, is essential.  The occurrence of different digestive enzymes in the alimentary canal of insects is mainly due to chemical composition of the diet ingested by them.  Enzymatic assays of the gut of Anticarsia gemmatalis in all instars were performed aiming at one better adaptative understanding of this insect to the diet change.  The caterpillars received two different treatments:  soy leaves and artificial diet.  The tested enzymes were amylase, lipase and protease using, as substrates, starch, tributyrate dithiopropanol and azocasein respectively, demonstrating an increase of the enzymatic activity during the life cycle, with peaks of activity in the fourth and fifth instars.  Moreover, the caterpillars created with artificial diet presented enzymatic activities superior to the ones of those created with soy leaves when proteases and amylase were analyzed. A possible cause of this disparity can be the presence of enzymatic inhibitors synthecized by the soy, which provokes a reduction in the activities.  As for the activity of lipase, it proved to be higher in the caterpillars created with soy.  This can be related with the highest use of lipids, in order to compensate the increase in the energy expenditure used for the production of more enzymes because of the presence of enzymatic inhibitors in soy leaves.