The frass of the pyrgo beetle (Paropsisterna tigrina) feeding on commercial plantations of the terpinen-4-ol chemical variety of the Australian tea tree.Melaleuca alternifolia, was found to contain a volatile oil almost identical to the essential oil of the ingested leaf. When beetles were fed leaf containing substantial quantities of 1,8-cineole, the predominant frass metabolite as determined by MS, IR,(13)C and(1)H NMR, GC, and CoGC was (+)-2β-hydroxycineole. Both male and female adults and larvae metabolizedMelaleuca oils in similar ways.