Journal of Chemical Ecology, Vol. 12, No. 6, 1986 EUPHYDRYAS ANICIA (Lepidoptera: Nymphalidae) UTILIZATION OF IRIDOID GLYCOSIDES FROM Castilleja AND Besseya (SCROPHULARIACEAE) HOST PLANTS 1 F R A N K R. S T E R M I T Z , 2 D A L E R. G A R D N E R , 2 F R A N C O I S J. O D E N D A A L , 3 a n d P A U L R. E H R L I C H 3 2Department of Chemistry, Colorado State University, Fort Collins Colorado 80523 3Department of Biological Sciences, Stanford University, Stanford, California 94305 (Received May 28, 1985; accepted September 25, 1985) Abstract--Iridoid glycosides were found to be sequestered by natural pop- ulations of Euphydryas anicia after ingestion from the host plants Besseya alpina, B. plantaginea, and CastiUeja integra. Both major iridoids of B. al- pina, catalpol and aucubin0 were found in butterfly populations where this was the only host plant. The catalpol-aucubin ratio was higher in the butter- flies than in the host plant. An E. anicia population which uses both B. plan- taginea and C. integra as host plants was found to sequester catalpol as well as another iridoid, macfadieuoside. Macfadienoside was the major iridoid of C. integra, while catalpol esters were the major iridoids of B. plantaginea. Although it was a major sequestered iridoid, catalpol was a minor constituent in both host plants. The macfadienoside-eatalpol ratio in the butterflies from this population was highly variable, and there appeared to be both sex and individual variation in host plant and/or iridoid glucoside utilization by E. anicia. Although other iridoids were present in the host plants, none was sequestered in more than trace amounts. Key Words--Euphydryas anicia, Lepidoptera, Nymphalidae, Castilleja in- tegra, Besseya plantaginea, Besseya alpina, iridoid glycosides, catalpol, macfadienoside, sequestration, plant-insect interactions, herbivory, ecolog- ical chemistry. J This work was supported by grant CHE-8213714 to FRS, in part by grant DEB-06961 to PRE from the National Science Foundation, and a grant from the Koret Foundation of San Francisco to PRE. Paper 5 in the series "Chemistry of the Scrophulariaceae." Paper 4: Roby, M.R. and Stermitz, F.R. 1984. J. Nat. Prod. 47:854-857. 1459 0098-0331/86/0600 1459505.00/0 9 1986 Plenum Publishing Corporation