Iridoid glycoside content ofEuphydryas anicia (Lepidoptera: Nymphalidae) and its major hostplant,Besseya plantaginea (Scrophulariaceae), at a high plains colorado site.

The checkerspot butterfly,Euphydryas anicia, utilizes mainlyBesseya plantaginea and only occasionallyCastilleja integra as a larval hostplant at Michigan Hill, a few kilometers from a site whereC. integra is used by over 90% of the butterflies. TheB. plantaginea leaves that are consumed contain 9-22% iridoid glycosides, composed mainly of catalpol and catalpol esters, while larvae from the same plants contain 6-18% iridoids, mainly catalpol and no esters. Field-collected adult butterflies contain 0.5-4.3% iridoids. Laboratory-reared adults secrete iridoids in the meconium upon eclosion and retain similar amounts. The adult and meconium iridoid content is considerably lower than in the larvae, and metabolism in the pupal stage may be occurring.