Abstract: Third-instar larvae of housefly (Musca domestica) were treated with different inducing methods including pricking, pricking with bacteria, heat shock, and ultrasonication, and collected at different times. The antibacterial activity was measured with liquid phase assay, and the antibacterial-related roteins/peptides were confirmed with stepwise regression model. The results showed that the above four treatments all could induce antibacterial substances. Among these induced proteins, X₁₆ (22 kD) had activity against Micrococcus luteus and Escherichia coli, but X₂ (50kD), X₁₂ (26 kD), ₂₂ (13 kD), X₂₄ (7 kD) only had activity against either M. luteus or E. coli, and X₇ (37 kD) had negative effect on antibacterial activity, which was deduced to be factors that stimulated cell to grow rapidly.

Key words: Musca domestica, inducement, antibacterial_relate d proteins/peptides, antibacterial activity