I just read this fascinating article in Science about antimicrobials and insects (avoiding resistance). Natural antibiotics are much less prone to creating resistance in bacterial populations. This group puts forth the hypothesis that insects use antimicrobials for long term clearance of bacterial infections, and not to fight the initial, large influx of bacteria (this is fought by the cellular arm of the insect immune system). This leads to less antimicrobial resistant bacteria. Contrast this, with our own clinical use of antibiotics. The uses a number of experiments to back their claim.
Here is the link: