Proteins in a nonvenomous defensive secretion: biosynthetic significance.

In common with many arthropods, the true bug, Leptoglossus phyllopus, when disturbed, emits a two-phase secretion that consists of an organic phase and an aqueous phase. The organic phase is a mixture of highly reactive low-molecular-weight compounds, analogous to those produced by other arthropods, and is deterrent to many kinds of predators. The aqueous phase, heretofore ignored in most analyses of arthropod defensive secretions, contains proteins. Even though the secretion is not injected, the proteins enzymatically catalyze the derivation of the most reactive components within the impermeable cuticular storage reservoir and, thus, constitute part of the defensive system that appears to be commonly used by arthropods producing irritating chemicals.