The effect of consuming low doses of E-64, a cysteine protease inhibitor, on life history parameters ofEpilachna varivestisMulsant, the Mexican bean beetle, was evaluated in bioassays in which E-64 was applied to lima bean leaves. Mortality, larval growth rates, and adult reproductive patterns were monitored and used to estimate life history parameters. Ingestion of this low dosage of E-64 increased the time to first oviposition, inter-egg mass interval, and number of days to complete larval development. E-64-fed females mated to E-64-fed males produced fewer eggs. There was no statistically significant difference between E-64-fed and control insects for either adult mortality, larval mortality, pupal weight or egg hatch (from E-64-fed females).On a per-day basis, insects fed E-64-treated leaves consumed similar amounts of leaf tissue to the control insects but, because of their longer larval development time, they required more leaf tissue to complete their larval development. The observed differences in life history parameters would potentially translate into large differences in population growth. The value of protease inhibitors for resistance against multivoltine specialist insects is discussed.