Cecropins are produced by insects, particularly under conditions of infection. Cecropins are bioactive peptides that exhibit activities by interacting with membranes and forming transmembrane channels that allow the free flow of electrolytes, metabolites and water across the phospholipid bilayers. Cecropins A, B and D are close homologues consisting of 35-39 residues. They are found in the pupae of the cecropin moth, but related homologues named lepodopteran, bactericidin, moricin and sarcotoxin are produced by other insects.