PRODUCTION OF CARDIAC-GLYCOSIDES BY CHRYSOMELID BEETLES AND LARVAE

Cardenolides were looked for in 17 chrysomelid beetles belonging to 11 genera from three subfamilies, and they were found only in Chrysolina and Chrysochloa species (Chrysomelinae, Chrysolinini). The food plants of these insects are not known to produce cardenolides. The Chrysochloa and most Chrysolina species secrete a complex mixture of cardenolides, but Chrysolina didymata secretes a single compound, and Chrysolina carnifex, none. Several quantitative and perhaps qualitative differences were observed in the patterns of cardenolides produced by far distant populations of both Chrysolina polita and C. herbacea, collected in either France and Belgium, or Greece. These differences remain constant from one generation to the other, whatever the food plant is, and appear to be genetic. In C. polita from Greece, the pattern is unchanged after four generations bred in the laboratory on Mentha ×villosa, which is known to be without cardenolides. In adults, the cardenolides are released with the secretion of the pronotal and elytral defensive glands, but in the larvae which lack the defensive glands, cardenolides are also produced. The total amount of cardenolides and the complexity of their mixture increases through the life cycle of the insects. The six main cardenolides secreted by C. coerulans were identified as: sarmentogenin, periplogenin, bipindogenin, and their corresponding xylosides. C. didymata secretes only sarmentogenin. © 1979 Plenum Publishing Corporation.