| Summary: | A group of toxic sulfur-containing polyynes (thiarubrines) exhibit significant lightmediated
antibiotic activity against microoroganisms particularly against fungi. These
phytochemicals have been isolated from several members of the Asteraceae including Ambrosia
chamissonis Less. (Greene), a species found along sandy beaches in British Columbia. The larvae
of a rare noctuid moth, Lasionycta wyatti (Barnes and Benjamin) (Lepidoptera: Noctuidae), were
found to be associated with the stems and roots of this plant. High performance liquid
chromatographic (HPLC) analyses of L. wyatti larvae and their frass found significant amounts of
thiarubrines. Artificial diets containing thiarubrines were shown to be tolerated by these larvae.
These same diets, however, were toxic to larvae ofManduca sexta (L.) (Lepidoptera: Sphingidae)
and growth inhibitory to larvae of Spodoptera litura (Hubner) (Lepidoptera: Noctuidae). The
combination of simulated sunlight and artificial diets containing thiarubrines, did not negatively
affect the larvae of L. wyatti. However, the incorporation of UV-activated thiophenes did
negatively affect the larvae of L. wyatti. Results of feeding assays suggest the escape mechanism
used by L. wyatti is its ability to rapidly eliminate thiarubrines from its tissues.
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