Diptericin is a 9 kDa antimicrobial peptide (AMP) of flies first isolated from the blowfly Phormia terranova.

A polymorphism at a single residue in the diptericin glycine-rich domain drastically affects its activity against the Gram-negative bacterium Providencia rettgeri.

This represents convergent evolution of an antimicrobial peptide towards a common structure in two separate fruit-feeding lineages.

[10][11] Diptericin B loss is also convergent among lineages feeding on mushrooms or plants, including the mushroom-feeding fruit flies Leucophenga varia, Drosophila guttifera and Drosophila testacea, and plant-feeding Scaptomyza flies.

[10] These observations are part of a growing body of evidence that antimicrobial peptides can have intimate associations with microbes, and perhaps host ecology, in contrast to the previous philosophy that these peptides act in generalist and redundant fashions.