Uptake of flavonoids from Vicia villosa (Fabaceae) by the Lycaenid butterfly, Polyommatus icarus (Lepidoptera: Lycaenidae)

Caterpillars of Polyommatus icarus were reared on inflorescences of Vicia villosa, a plant species acceptable for larval development, but not used as food source in nature. Vicia villosa flowers contained four flavonoids at a concentration of 18.34 mg g(-1) dry weight. Three compounds were identified by MS and NMR as myricetin-3-O-rhamnoside (8.68%), quercetin-3-O-rhamnoside (56.30%), and kaempferol-3-O-rhamnoside (32.18%). Larvae incorporated and metabolized only part of the flavonoids of their hostplant, while a larger proportion was excreted. Besides trace amounts of metabolites, adult butterflies contained mainly quercetin-3-O-rhamnoside and kaempferol-3-O-rhamnoside at a total concentration of 1.22-1.38 mg g(-1). The main flavonoid in the butterflies was kaempferol-3-O-rhamnoside (55%). Females stored more flavonoids than males, and the flavonoid content was correlated with body mass. Butterflies raised on V. villosa as larval food differed qualitatively (number and chemical nature of flavonoids) and quantitatively from conspecifics reared on other hostplants. It is proposed that quantitative variation of flavonoids, which are incorporated into the wing patterns, could serve as a means of mate recognition and selection. (C) 1997 Elsevier Science Ltd.