This work reports the effects of DrTI on proteinases of Anagasta kuehniella and Corcyra cephalonica larvae after incorporation in artificial diet.  The larvae were maintained in plastic boxes, with perforated plastic lid at a relative humidity of 65-70%, temperature at 28ºC. Two treatments to feed the larvae were made, one without DrTI and other containing 1.0% of DrTI.  Each treatment was repeated 5 times with 10 larvae (n=50). The results were analyzed using ANOVA and Tukey test to determine the level of significance (p < 0.05). The trypsin inhibitory activity was determined using the substrate DL-BApNA and for chymotrypsin were used the substrates BTpNA and SAAPFpNA at a final concentration of 1 mM in DMSO 1% (v/v). The artificial diet containing 1.0% of DrTI was inefficient to affect the survival and mean weight of both insects, but stimulated the chymotrypsin-like enzymes activity (11.3%) in A. kuehniella, suggesting that these enzymes probably are insensible to DrTI and also can be employed for proteolytic digestion. On the other hand, trypsin residual activity of DrTI-fed A. kuehniella larvae was ca. 20%. Midgut and faecal extracts from A. kuehniella larvae fed with artificial diet and with DrTI at 1.0% were incubated with TLCK (100 mM) during 10 min at 30ºC. Proteinases activities were monitored by SDS-PAGE in gels containing 0.1% gelatin with different treatments (midgut + DrTI, midgut + TLCK, excrement + DrTI, excrement + TLCK, midgut + DrTI + TLCK and excrement + DrTI + TLCK). Electrophoretic analysis of these treatments showed that TLCK inhibited the most of trypsin-like enzymes, while DrTI probably induced the synthesis of insensitive enzymes to TLCK. Additionally, tryptic test with excrement showed reduction of enzymatic activity, indicating that DrTI not was cleaved by enzymes of midgut. Our data can contribute on understanding the dynamic nature of insect midgut proteinases at molecular level.