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Iridoid glycoside sequestration by Thessalia leanira (Lepidoptera: Nymphalidae) feeding on Castilleja integra (Scrophulariaceae)

Mead, E.W., Foderaro, T.A., Gardner, D.R., Stermitz, F.R.
Journal of chemical ecology 1993 v.19 no.6 pp. 1155-1166
Nymphalidae, feeding behavior, Castilleja, iridoid glycosides, Colorado
A small population of a polyvoltine checkerspot butterfly, Thessalia leanira fulvia (also known as Chlosyne leanira ssp. fulvia), was found to use Castilleja integra as a larval food plant at a localized site (Burnt Mill) southwest of Pueblo, Colorado. Field-captured adult butterflies contained the major iridoid glycosides (catalpol and macfadienoside) of the Castilleja. The content of a third iridoid glycoside, methyl shanzhiside, was also relatively high in the collected butterflies even though most individual Castilleja plants at Burnt Mill contained little or no methyl shanzhiside. Only a few plants, restricted to a small area, did contain appreciable methyl shanzhiside. Most of the plants that lacked the ester methyl shanzhiside contained shanzhiside, the corresponding free carboxylic acid. Thessalia larvae did not normally methylate the acid to produce methyl shanzhiside. Larvae that stopped feeding at an early instar, but yet survived several weeks, did contain major amounts of methyl shanzhiside. It is suggested that only larvae that overwinter or otherwise enter diapause convert shanzhiside to methyl shanzhiside. The Castilleja food plant also contained iridoids other than catalpol and macfadienoside, sometimes in major amounts, but these were never found in larvae, pupae, or butterflies.