SEQUESTRATION AND METABOLISM OF HOST-PLANT FLAVONOIDS BY THE LYCAENIDBUTTERFLY POLYOMMATUS-BELLARGUS

Larvae of the lycaenid butterfly Polyommatus bellargus were reared on leaves of Coronilla varia that are rich in flavone C-glycosides. Six f lavonoids including isovitexin and isoorientin, as well as several of their congeners were isolated and identified by spectroscopic means. C omparative HPLC analysis of the host plant and of larvae, pupae, and i magines of P. bellargus indicated selective uptake of isovitexin versu s isoorientin derivatives. Isovitexin-2 ''-O-xyloside was the major fl avonoid detected in pupae and in imagines of P. bellargus. Several min or components were tentatively identified as quercetin- and kaempferol -O-glycosides based on their on line-UV spectra and by comparison with known standards. Since leaves of the host plant accumulate exclusivel y flavones, the flavonol glycosides are considered to be biotransforma tion products that are formed by the insects and/or by symbiotic bacte ria. Imagines of P. bellargus caught in the wild exhibited similar fla vonoid patterns compared to imagines reared in the laboratory. Within the imagines, approximately 80% of all flavonoids are stored in the wi ngs (especially in the orange submarginal lunules), whereas the remain ing 20% resides in the bodies. Female butterflies show a significantly higher flavonoid concentration than males. It is suggested that the s equestered flavonoids are involved in visual mate recognition.