Three cDNA clones encoding the partial sequence of the antimicrobial factor-like peptide were isolated from the fat body of the cabbageworm, Artogeia rapae immunized with E. coli K12. Nucleotide sequences of three cloned genes have a high degree of homology one another. The primary structure analysis revealed that their deduced amino acid sequences showed the characteristics of the cecropin family antibacterial peptides and that the amino acid residues which are highly conserved in the antibacterial peptides from moths and flies are also conserved in butterfly, implying that these clones are encoding the antibacterial peptides.