Cyanogenesis and the role of cyanogenic compounds in insects.

The cyanogenic system comprising cyanogenic glycosides, hydroxynitriles (cyanohydrins), beta-glucosidases and nitrile lyases is widespread in the plant kingdom but also occurs in several arthropods. A few insects were found to contain mandelonitrile and, in one case, a small amount of prunasin was detected. Cardiospermin and gynocardin occur in one insect, and the cyanoglucosides linamarin and lotaustralin are found in several species of the lepidopterans. Biosynthesis of these cyanoglucosides has been studied in two of these species and their sequestration has been investigated in one species. For Zygaena trifolii the presence of the entire cyanide-handling system indicates an important function of these compounds. So far, their function as defensive compounds seems likely on the basis of their ability to generate HCN and their localization, and appears to be indicated by some feeding experiments with potential predators.