Juvenile hormone identification in the cabbage bug Eurydema rugosa

Juvenile hormone (JH) plays a pivotal role in almost every aspect of insect development and reproduction. The chemical structure of the JH in heteropteran species has long remained elusive until methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate, commonly named as juvenile hormone III skipped bisepoxide (JHSB₃), was isolated from Plautia stali (Hemiptera: Heteroptera: Pentatomidae). Recently, several groups reported the presence of JHSB₃ in other heteropteran species. However, most of the studies paid no attention to the determination of the relative and absolute structure of the JH. In this study, we investigated the JH of the cabbage bug Eurydema rugosa (Hemiptera: Heteroptera: Pentatomidae), known as a pest for wild and cultivated crucifers. JHSB₃ was detected in the hexane extract from the corpus allatum (CA) product using a chiral ultraperformance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) which can inform the absolute stereochemistry of the JH. Its stereoisomers were not detected. Topical application of the synthetic JHSB₃ to the last instar nymphs inhibited their metamorphosis and induced nymphal-type colouration of the dorsal abdomen in a dose-dependent manner. Additionally, the topical application of JHSB₃ effectively terminated summer and winter diapauses in females. These results indicate that the JH of E. rugosa is JHSB₃. Although individuals in summer and winter diapauses are physiologically distinct in E. rugosa, the results suggest that the physiological differences between these diapauses are based, not on the responsiveness to JH, but on the processes governing activation of the CA or on its upstream cascades.